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Electronics - Microprocessor Systems Hardware

1. Function Example using Symbolic notation Comment DEBUG syntax Add with ADC AL 08 AL AL 08 C immediate data Carry ADC AL BL AL AL BL 4 C register data ADC AL 0200 AL lt AL 0200 C memory data In the above instruction after execution AL contains the sum of the previous contents of AL the source data and the value of the c flag Note the c flag should be cleared for the first ADC instruction Subtract SUB CX 0A CX amp CX 0A immediate data SUB AL CL AL AL CL register data SUB AL 0200 AL AL 0200 memory data In the above instructions after execution the destination register contains the difference of the initial value of the destination element and the source data Increment INC AL AL AL 1 increment AL by 1 Decrement DEC AL A amp AlL 1 decrement AL by 1 The value of the specified element is incremented decremented by 1 76 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Logical operations These operations are performed in a similar way to the arithmetic operations One number is held in the destination element and the other in the source register memory or is immediate data the result is returned in the destination register Sample logical instructions are tabulated below Function Example using Sym
2. This leaves 14019 12810 1210 40 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Now highest column that can be set is 8 This leaves 1219 810 410 to be converted Now highest column that can be set is 4 This leaves 4 5 410 0 to be converted The result is given below 128 64 32 16 8 4 2 1 1 0 0 0 1 1 0 0 14019 1000 1100 SAQ 1 Convert the following decimal numbers into binary a 1510 b 3810 c 12710 d 14810 e 25510 SAQ2 Convert the following binary numbers into decimal a 0000 11115 b 1010 10105 ep 011111112 d 1100 1100 e 01100110 In microprocessor based systems the microprocessor operates on 8 or more bits at any one time Some microprocessors can handle 64 bits or more of data at one go This makes the binary system rather tedious and cumbersome to use these days hence the hexadecimal system is more popular The hexadecimal system The hexadecimal system or hex uses 16 symbols 0 to 9 decimal plus A to F alphabetic and has a base of 16 Each column has a weighting of 16 where n is the column position number as shown below in table 5 Table 5 Hexadecimal system 16 16 16 16 4096 256 16 1 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 41 Learning and Teaching Scotland MICR
3. Learning and Teaching Scotland ANSWERS TO SAQs b INT Ratc INT Rep main process main process ISRartc ISRep SAQ22 i 1001 1011 9By ii 1001 1000 984 iii 1011 X10X B4y iv 11XX XXXX gt CO v 1010 1111 AFy 148 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland
4. INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING Flowchart Purpose ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 97 Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING program prog15_pas program name uses crt const porta 284 equ portb porta l porte porta 2 ctrlreg porta 3 ctrlbyte 89 var mem1 mem byte not used in this program begin asm start mov al ctrlbyte configure ports mov dx ctrlreg out dx al mov dx portc read portc in al dx mov dx portb write portb out dx al call delay call subroutine xor al ff process out dx al call delay subroutine again jmp start repeat delay time delay subroutine mov ch 0ff loop2 mov cl 0ff loopl dec cl jnz loop 1 dec ch jnz loop2 ret return from subroutine end end of assembly end end of file 98 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING Flowchart Purpose ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 99 Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING Bit masking In engineering control programs decisions need to be made on the state of individual bits in a byte Alternatively individual bits in a byte require to be set or reset When individual bits ar
5. Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Memory organisation A standard 8 bit microprocessor has a 16 bit address bus The 16 address lines are labelled Aj to Ao A 5 being the MSB and Ag being the LSB Similarly the 8 data lines are labelled D to Do Sixteen address lines can directly address 2 65 536 memory locations In computer jargon 1k 1024 Assuming that the memory is 1 byte wide how many kilobytes of memory can be addressed by the 16 address lines Yes 65536 1024 64k This 64 k of memory address space can be fitted with RAM ROM and I O devices A memory map is a diagram that shows how various devices occupy the memory space and what functions are assigned to the different areas of the memory A sample memory is given below Figure 9 A memory map FFFFy I O Memory 8K mapped I O E0004 DFFFy VRAM Video 8K memory C0004 BFFFy Disk drive buffer RAM amp 16K interrupt vectors 80004 TFFFy User RAM programs 16K and data 40004 3FFFy Executive ROM program 16K 00004 58 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Port addressing The figure 9 memory map includes the I O port addresses This means that the I O interface is treated as memory and that memory instructions are used for I O operations The advantage of this is that no special instructions need to be
6. Mode Definition Summary INTR Interrupt STB Strobe IBF Input Buffer Full ACK Acknowledge OBF Output Buffer Full 118 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Detailed operation of port A in Mode 1 of the 8255 Port A as an input port Figure 31 Port A as I P in Mode 1 Input device INTRA To microprocessor The input device places data on port bit PA7 to PAO and then sends an active low strobe STB A on PC4 This strobe latches data into port A The PPI automatically generates an active high input buffer full signal BF on PC5 to the input device IBF PC5 high lets the input device know that data has been reviewed but not yet read The microprocessor also monitors IBF to determine if data is available If IBF A is high it reads port A and IBF A is reset This signals to the input device for more data This handshaking process for an input cycle is shown below Figure 32 Handshaking signals for port A as I P in Mode 1 Data from STB A yf n F ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 119 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Figure 33 Port A as O P in Mode 1 Output Device INTR A Port A as an output port output data VALID DATA OBF A TE _ ACK A G S Handshake signals The microprocessor writes
7. An outline of the outcomes to be covered in the unit The assessment instruments for the outcomes The required achievement standard for each assessment Candidate s guide to working on the unit Safety guidelines for electronics microprocessor laboratory work Microprocessor systems hardware Introduction to assembly language programming Data transfer techniques 15 17 25 27 30 32 33 35 37 91 103 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH iii Learning and Teaching Scotland CONTENTS Section C9 Programmable peripheral interface PPI 113 Section C10 Tutorial questions 135 Section C11 Answers to SAQs 139 iv ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL RY OP WOT ERY Outcomes to be covered in the unit Outcome 1 Describe a microprocessor based system Performance criteria a Given the block diagram of a microprocessor based system the function of each block is clearly described b Describe the internal architecture of a microprocessor c Semiconductor memory memory organisation and memory decoding techniques used in microprocessor systems are clearly explained d The basic instruction cycle and system bus functions are clearly explained Note on the range of the outcome Microprocessor based system memory devices microprocessor input output int
8. TASM and DEBUG of DOS Assembly language programs can also be embedded in high level languages such as Turbo PASCAL ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 85 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE An assembly language program consists of statements Each statement can have four fields or parts The fields are separated by spaces The first field is followed by a full colon and the last field is preceded by a semi colon A sample statement example is given below Start Label mov al 89H Op Code control byte in al Operand Comment The label identifies the line and represents the address of the instruction The OpCode operation code is a valid mnemonic instruction or an assembler directive see later The operand represents information required by the mnemonic instruction This may be registers or memory addresses etc Comments are preceded by a semi colon and are ignored by the assembler Comments are used to convey the purpose of the instruction to the user reader of the program Assembler directives Mnemonic instructions are for the microprocessor Assembler directives are for the assembler to assign names to constants assign storage areas etc Common 8086 directives are listed below 486 CODE DATA DB DW DUP DOSSEG EQU END EXIT MODEL ORG ensure that 80486 is valid default 8086 inform the assembler
9. b2 bs bo by 102 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland DATA TRANSFER TECHNIQUES SECTION C8 Candidate notes Peripheral devices are connected to a microprocessor to allow data to be sent received between the outside world and the microprocessor system The peripheral devices may be connected using memory mapped or I O mapped techniques The data can be transferred in serial form or parallel form Serial data transfer sends the data down a 2 wire communication link 1 bit at atime This method is slow but is useful when data has to be transferred over a long distance at low cost Parallel data transfer has communication lines of the same width as the ports of an I O interface chip usually 8 bits in a microprocessor system Therefore in parallel data transfer 8 bits are normally transferred at one go Parallel data transfer is normally used over short distances and is much faster more expensive and uses more cables than serial data transfer Parallel data transfer may take place e between a microprocessor and memory e between a microprocessor and I O chip e between and I O chip and peripheral device Data transfer may be synchronous or asynchronous ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 103 Learning and Teaching Scotland DATA TRANSFER TECHNIQUES Synchronous parallel data transfer Synchronous parallel
10. c Adda 1 to the result of the inversion and the 2 s complement representation of the negative number is formed Example Express the 4919 and 499 in 2 s complement representation and show that their sum is 0 491 0011 0001 Invert all bits 1100 1110 Add 1 1 49 1 1100 1111 Proof 49 0011 0001 49 11001111 Addition 0 1 0000 0000 ignore carry if any SAQ7 Using byte size data express in hex the 2 s complement of the following numbers a 1 b 1 c 127 d 127 e 2 44 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Logical operations A microprocessor is capable of performing many different types of operations on data such as e Arithmetic operations add subtract e Logical operations AND OR NOT shift and rotate Some of these are discussed next before the actual hardware architecture is considered Truth tables for arithmetic functions Addition Subtraction A B A B Carry A B A B Borrow 0 0 0 0 0 0 0 0 0 1 1 0 0 1 1 1 1 0 1 0 1 0 1 0 1 1 0 1 1 1 0 0 Truth tables for logical operations AND OR EXCLUSIVE OR NOT A B A B A B A B A B A B A IA 0 0 0 0 0 0 0 0 0 0 1 0 1 0 0 1 1 0 1 1 1 0 1 0 0 1 0 1 1 0 1 1 1 1 1 1 1 1 1 0 Logic gates which are capable of carrying o
11. 16 8 lt gt Names 32 bit 16 bit 8 bit EAX AH AL _ Accumulator EAX AX AH AL Base index EBX BX BH BL Count ECX CX CH CL Data EDX DX DH DL Stock pointer ESP SP uses SS Base pointer EBP BP uses SS Destination EDI DI uses ES index Source index ESI SI uses ES EIP Instruction EIP IP uses CS pointer Flags EFLAGS FLAGS Code Data Extra Stack Note 1 The shaded areas are not available to the 8086 8088 or 80286 microprocessors Note2 No special names are given to the FS and GS registers ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 71 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Of immediate interest are the general purpose 16 bit registers AX BX CX and DX These can also be used as two 8 bit registers For example AX may be treated as AH and AL 8 bit registers The code segment CS register is normally used with the IP register to generate the program execution addresses The programmer s model also shows the flags register which is composed of individual bits These bits are used to indicate events that occur inside the microprocessor The z flag is set that is z 1 when the result of an operation is zero The c flag is set when the result of an addition operation gives a carry forward The c is also used to hold the overflow in shift and rotate operations as shown below Shift left Before x 0 0 1 1 0 0 1 1 c After o k lolili
12. b an RTC interrupt is immediately followed by a floppy disk interrupt In a microprocessor system there are hardware external interrupts and software internal interrupts not considered on this course which are given priority as follows e Internal interrupts software highest priority e Non maskable interrupts NMI hardware e Maskable interrupts INTR hardware e Single step interrupt hardware lowest priority There are many sources of external maskable interrupts and these are assigned priority using software or hardware techniques The hardware method uses a chip known as a Priority Interrupt Controller 112 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI SECTION C9 Candidate notes All peripheral devices are connected to the microprocessor by electronic interface circuits These interface circuits may involve serial or parallel data transfers between the peripheral device and the interface circuit A parallel interface connection is shown below Figure 27 Interfacing the microprocessor to the real world Interface Peripheral Device Microprocessor Circuit The real physical word In parallel data transfer all 8 bits of data a byte are transferred simultaneously between the interface circuit and the peripheral device The 8 bit connection on the interface circuit is normally referred to as a port The ports may be m
13. 0200h and 0201h after program execution Answer Location 0200h will store aah and 0201h will store 55h Program 2 mov al 0200 mov ah 0201 mov 0201 al mov 0200 ah int 20 Question What will be stored in location 0200h and 0201h after program execution Answer 0200h will contain 55h 0201h will contain aah Program 3 mov al 0200 and al 0201 mov bl al mov al 0200 or al 0201 mov bh al mov al 0200 and al Of mov 0200 al or al 0201 mov 0201 al int 20 Question Assume initially 0200h and 0201h contain aah and 55h respectively Work out the contents of bh bl 0200h and 0201h after execution of the program ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 79 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Answer bh contains ff h bl contains 00 h 0200h contains Oah 0201h contains 5fh Program 4 mov al 0200 cmp al aa jnz branchl branch2 int 20 branchl mov al 00 mov 0200 al jmp branch 2 In reality branch 1 and branch 2 are addresses or relative number of memory location to be jumped in two complement form Question What will be contained of 0200h after program execution if 0200h initially contained a aah b 55h Answer a aah b 00h The flow chart for this program is given below Compare with aah store 00h in 0200h 80 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and T
14. 2 ctrlreg porta 3 ctrlbyte 89 on ff off 00 begin asm call config loop mov dx portc in al dx read port C cmp al ff je finish port C 255 then end mov dx portb mov al on out dx al LEDS on call wait delay mov al off out dx al LEDS off call wait delay jmp loop repeat Sub Programs config mov dx ctrlreg configure ports mov al ctrlbyte subroutine out dx al ret ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 127 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI wait mov bx ffff delay subroutine loop2 mov cx 0fff loop1 dec cx jne loopl dec bx jne loop2 ret finish end end 128 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Example ports 3 In a control process the level of a liquid is required to be monitored by two sensors Sensor S1 monitors the lower limit and sensor S2 monitors the upper limit When the liquid level is above the upper limit the supply pump is to be switched off If the liquid level falls below the lower limit an alarm is to be raised The operation of the system is summarised below S2 S1 Alarm Pump 0 0 1 0 0 1 0 1 1 0 1 0 1 1 0 0 Sensors S1 and S2 are connected to bits PC3 and PC4 of port C respecti
15. Performance criteria a Given the block diagram of a programmable peripheral interface PPI integrated circuit its operation is clearly explained b Using a manufacturer s data sheets a programmable peripheral interface integrated circuit configuration is designed to meet a given specification c Given suitable software and hardware a programmable peripheral interface integrated circuit is configured and tested to meet a desired specification Note on the range of the outcome The range for this outcome is fully expressed in the performance criteria Evidence requirements Written and graphical evidence that the candidate can explain the operation of a programmable parallel interface integrated circuit Performance evidence that the candidate programmes and tests a programmable parallel interface integrated circuit Outcome 4 Modify an assembly language program Performance criteria a A given functional assembly language program is analysed and its operation is clearly explained b A specified operational change for the assembly language program is correctly designed c The specified operational change for the assembly language program is implemented and tested until fully functional 2 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Note on the range of the outcome The range for this outcome is fully ex
16. SYSTEMS HARDWARE Introduction to assembly language programming Assembly language involves the use of mnemonic instructions in software development The software is then translated into machine code binary code by an assembler program so that the program can be run through the microprocessor circuitry Assembly language programming requires an intimate knowledge of the microprocessor architecture and instruction set The architecture of an 8 bit microprocessor has been outlined in the previous section The microprocessors used in modern systems are much more sophisticated but the basic principles are similar Many present day PCs use microprocessors based on the 8086 microprocessor and have a large user base This introduction to assembly language is centred around the 8086 microprocessor 8086 microprocessor architecture The internal architecture and pin out of the 8086 microprocessor is shown below 40 21 20 8086 PIN OUT 68 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Figure 16 The 8086 internal block diagram Execution Unit Bus Interface Unit EU BIU Segment Registers Instruction Pointer General Purpose Register Address Generation and Bus Control Multiplexed Bus Instruction Queue FLAGS Execution Unit Control System The 8086 consists of two main sections the bus interface
17. and Teaching Scotland DATA TRANSFER TECHNIQUES Polling Normally many devices are connected to a microprocessor system and polling is a method used to determine which peripheral devices require service i e require to send or receive data The microprocessor periodically checks in a pre determined sequence the flags in the I O interface chips to determine which device requires service If a device is ready data transfer takes place otherwise the next device is checked or the main program is executed An example of a polling sequence is shown below Figure 23 Polling sequence placed at regular intervals in the main program main program Is a device ready for data transfej No Yes Identify Device Peform Data Transfer Main Program Polling is simple to implement but has a number of disadvantages a It slows down the execution of the main program b Since polling is a regular activity some devices may be interrogated more often than necessary c Devices may become active immediately after they have been polled and this may result in loss of data due to the time lag in being polled again To reduce the polling overhead and make the system more efficient interrupts are used for I O data transfers rather than polling ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 107 Learning and Teaching Scotland DATA TRANSFER TECHNIQUES Interrupts In an interrupt driven system
18. assessment should assist teachers and lecturers to identify why an individual candidate has failed to achieve a particular outcome and to plan focused support for learning For all the outcomes the reassessment should be based on the original instrument of assessment When candidates have not produced a satisfactory answer to a section of an assessment they should only be asked to repeat those sections in which they have not provided suitable responses Candidates should be asked to complete the reassessment under the original controlled conditions This reassessment should take place as soon as practicable after the initial assessment and after discussion and analysis of the initial assessment has taken place between the candidate and the assessor Candidates should be informed of the sections of the assessments that they are required to repeat and given additional teaching to help them tackle the reassessment When there is a substantial number of candidates requiring reassessment a revision lesson on the problem area should be presented before reassessment Candidates may produce an answer that is substantially correct but contains minor errors such as the mislabelling of a diagram or the incorrect reading of an instrument 1011 0011 being C3y instead of B3y In this situation candidates should be reassessed by asking them to give the correct answer orally This should take place as soon as possible after the initial assessment and before any
19. candidates should be given opportunities to attempt questions on the microprocessor based system and memory implementation similar to those likely to be encountered in the end of topic assignment and test This will reinforce teaching while preparing the candidate for assessment The class test involves the completion of a pro forma and should be allocated about 90 minutes The memory implementation assignment should be returned within one week of issue and it should be an integrated learning and assessment activity with emphasis clearly on learning while assessment evidence is generated as a natural by product Outcome 2 assessment is a class test on data transfer techniques which should be delivered after the teaching of that topic As an integral part of the teaching candidates should be given opportunities to attempt questions on data transfer techniques similar to those likely to be encountered in the end of topic assignment and test This will reinforce teaching while preparing the candidate for assessment The class test involves the completion of a pro forma and should be allocated about 60 minutes Outcome 3 assessment a laboratory assignment on the programmable peripheral interface PPI should be delivered after the teaching of that topic As an integral part of the teaching candidates should be given opportunities to attempt questions on PPI configuration similar to those likely to be encountered in the end of topic laboratory assig
20. in the memory or read retrieved from the memory If the address bus is 16 bits wide then pan 65 536 memory locations can be directly accessed The lowest memory address being 0000 0000 0000 0000 0000p and the highest address being 1111 1111 1111 1111 FFFFy The following diagram illustrates how an instruction is retrieved from the main memory of a microprocessor system 52 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Figure 7 Memory read process data bus Memory Control amp Address Decoding Circuitry selected location microprocessor address bus The instruction pointer program counter sends out the correct address on the address bus and then automatically the contents of the IP PC are incremented by one Once the appropriate memory location has been selected the read signal is activated The contents of the selected location appear on the data bus and are read into the microprocessor The microprocessor instruction format A microprocessor has an instruction set which is a list of all the instructions the microprocessor can execute A program is a selection of these instructions and some data that is stored in contiguous memory locations In general the format of a microprocessor instruction is Operation code Operand where the operand may be an address or data or may not exit Hence a microprocessor ins
21. modifying assembly language programs The assessment instrument is a laboratory assignment in which you will be asked to explain the operation of given assembly language programs modify the given programs to meet new criteria and test the resulting code until functional In common with Outcome 3 you will require access to a computer with appropriate software assembler and associated hardware interfaces If necessary you should seek clarification from your lecturer teacher before you start the laboratory exercise review your progress as you proceed and submit your pro forma report for comment on completion The laboratory exercise for Outcome 4 should take about 120 minutes to complete ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 31 Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL SECTION C3 The required achievement standard for each assessment Outcome 1 Microprocessor based System Assessment The class test questions and the assignment are designed to match the performance criteria for the outcome Because of this you will have to reach a minimum standard in both the class test questions and the assignment to gain a pass Outcome 2 Input Output Data Transfer Assessment The class test questions are designed to match the performance criteria for the outcome Because of this you will have to reach a minimum standard in the test questions to gain a pass Outcome 3 Programmab
22. multiplying digits by their column weightings and summing the results is used to translate a number expressed in any number system into the decimal system Counting in the binary system is carried out in exactly the same manner as the decimal system that is once all symbols in a column are used then the next significant column is used Table 4 shows counting in the binary and decimal systems ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 39 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Table 4 Decimal and binary numbers Decimal Binary Tens Units Sixteens Eights Fours Twos Units 0 0 1 1 2 1 0 3 1 1 4 1 0 0 5 1 0 1 6 1 1 0 7 1 1 1 8 1 0 0 0 9 1 0 0 1 1 0 1 0 1 0 1 1 1 0 1 1 1 2 1 1 0 0 1 3 1 1 0 1 1 4 1 1 1 0 1 5 1 1 1 1 1 6 1 0 0 0 0 1 7 1 0 0 0 1 Converting decimal numbers into binary numbers 1 Identify the highest significant column that can be set to a 1 and set it to 1 2 Subtract this value from the decimal number to get the next number to convert 3 Repeat steps 1 and 2 until the number to convert is 0 4 Set the blank columns to 0 Example convert 1409 to binary 128 64 32 16 8 4 2 1 The column above 128 column has weighting of 256 hence the column 128 is the highest that can be set to a 1 128 64 32 16 8 4 2 1 1
23. out as follows a The microprocessor places a data byte onto the output port b Then it activates the DAV signal DAV 1 to inform the peripheral device that data is now available Also a flag may set in the I O chip to indicate that this event has occurred c The microprocessor then monitors the DACC signal to determine whether or not the data has been read by the peripheral device The flag may be checked for a reset condition d The peripheral device monitors the DAV signal If it is active DAV 1 it reads the data e Then the DACC signal is activated to inform the microprocessor that the peripheral device is ready for new data At this point the flag in the T O chip is also reset f This process continues until all the required data is transferred ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 105 Learning and Teaching Scotland DATA TRANSFER TECHNIQUES The handshaking process is shown below Figure 21 Handshaking for output cycle Data on port valid data DAV DACC data read by peripheral device SAQ19 Explain the sequence of events that take place when a microprocessor receives data from an input device as illustrated below Figure 22 Asynchronous input to microprocessor system Note the direction of the handshake signals has been reversed Input microprocessor Interface Device 106 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning
24. read and write operations may also be used ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 63 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE DATA LINE EEPROM E PROM WWORDLINE EAROM Structure based on SRAM Programmable ROM is manufactured with the links intact Once the binary pattern to be fitted in the device has been decided the data program is then burned into the PROM by blowing the links fuses using a PROM programmer Once a fuse has been blown it cannot be reconfigured and the PROM becomes a ROM random access read only non volatile memory Mask programmable ROMs are also available Erasable PROM is based on the stacked gate memory which is a combination of a FET and FAMOS cell In the unprogrammed state the EPROM cell stores a logic 1 however by applying a large programming voltage pulse it can be made to store a logic 0 The memory stacked MOSFET cell can be returned to its non conducting state by shining UV light onto the cells through the chip s quartz window The disadvantage of the EPROM is that it requires a UV light and twenty minutes to erase the chip Electrically erasing and programming the PROM is much faster hence their EEPROMS popularity over EPROMS The EEPROM cell consists of a MOSFET in series with stacked gate cell By applying a positive voltage pulse at Vcg the floating gate acquires a charge to store logic 1 If a negative v
25. teaching laboratory It is good practice to both commercially and technically survey the market to ensure that the best suppliers are offered sales opportunities Other centres that have tried and tested equipment are often the best source of information and should be consulted as part of the purchasing exercise Suppliers may provide access to users of their products who are prepared to discuss their experiences with others Time spent on this will pay substantial dividends in future years in terms of equipment downtime and repair costs Bytronics Supplier of interface and application boards for PCs Web address http www bytronic co uk E mail sales bytronic co uk Telephone 0121 378 0613 Fax 0121 311 1774 Address The Courtyard Reddicap Trading Estate Sutton Coldfield West Midlands B75 7BU Software The electronics microprocessor teaching laboratory is greatly enriched by the presence of PCs with appropriate software Since computers are one of the main products of electronics technology they find extensive use in the application of the technology and form part of the electronics environment While the capital outlay for this may be significant there has to be recognition of the part played by the computer with specialised software in the electronics environment Through access to suitable computing facilities and software candidates should be exposed to this environment in the teaching laboratory Commercial software for wor
26. that the following section contains code rather than data informs the assembler that the following section contains data for the program rather than program instructions define Byte directive is used to allocate memory space to a byte size variable for example DATA X DB 8 this means x is a variable initialised to the value 8 The value 8 is stored at the address of variable x define word directive is used to allocate memory space to a word 2byte size variable this is used with the DB directive to define an array of variables defines logical segment order informs the assembler to assign a constant value to a symbol informs the assembler that this is the last line of code causes the assembler to generate code to exit from program and to return control to DOS informs the assembler of the program size sets the location for the machine code 86 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE STACK sets the size for the stack default 100H bytes STARTUP causes the assembler to generate the necessary code at the start of the program TITLE allows the programmer to quote the name of the program or the file Another five programs are now presented using Microsoft Macro Assembler 6 0 MASM Note that when creating a source file using MASM memory locations are given a variable name for example meml and the assembler computes the actual addres
27. through to 9 This results in each column in the decimal system having a weighting of 10 where n is the column position number This is shown in table 2 Table 2 Decimal system Thousands Hundreds Tens Units 10 10 10 10 1000 100 10 1 38 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE The decimal number 123 really means 1x10 2x10 310 1x100 2x10 3x1 100 20 3 12310 Note the subscript 10 here is used to indicate the base of the number in this case decimal Counting in decimal is achieved by starting with 0 and adding 1 continuously until the 9 symbols in a column are used then a 1 is carried into the next significant column This is similar for all number systems The binary number system The binary number system uses only two symbols hence has a base of two and each column weighting is given by 2 where n is the column position number This is illustrated in table 3 below Table 3 Binary system Hundred Sixty Thirty Sixteens Eights Fours Twos Units amp twenty fours twos eights 27 26 De 74 De Je 2 2 128 64 32 16 8 4 2 1 The binary number 10111 really means 1x24 0x2 1x2 1x2 1x2 1x16 0x8 1x4 1x2 1x1 16 0 4 2 1 2310 The number 10111 is equal to 2319 Note This method of
28. to the local bus via special connections known as bridges or bus arbitrators The main components of the block diagram are described next Component PC or IP program counter or instruction pointer SP stack pointer GPR general purpose registers A accumulator ALU arithmetic logic unit Shifter SR status register or flags Description The PC always points to the next instruction in memory to be executed Its contents are propagated down the address bus to memory and once an instruction has been fetched its contents are automatically incremented The SP points to an area of memory which operates on the principle last in first out LIFO The stack is very useful for saving the state of the microprocessor in the event of an interrupt or subroutine call and parameter passing The programmer may use the general purpose registers as desired However some of these registers may have a special role for example the DX register on the 8086 is a GPR but it is the only one used for I O addressing The accumulator acts as a source and a destination for data in I O operations This register holds the result of arithmetical logical operations The ALU carries out operations on two pieces of data and normally stores the results in the accumulator The shifter carries out shift and rotate operations on data held in the accumulator The flags indicate the state of the microprocessor or the state of the res
29. var meml mem2 byte begin writeIn Enter a number in the range 0 to 255 readIn mem1 asm mov al mem and al 80 cmp al 80 jz half shl al 1 mov mem2 al jmp finish half shr al 1 mov mem2 al finish end end SAQ18 program saq18 uses crt var meml1 byte begin WriteIn Enter a number 0 to 255 ReadIn mem1 asm mov al mem and al aa shr al 1 mov ah al mov al mem and al 55 shl al 1 or al ah mov mem1 al end WriteIn With adjacent bits exchanged the byte is mem1 end 146 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland ANSWERS TO SAQs SAQ19 Data on DAV DACC data read by microprocessor The handshaking is similar to that shown in figure 21 This time the peripheral device places data on the input port pins and informs the microprocessor that data is available by activating the DAV signal Once the DAV line has been activated the microprocessor takes the data when its ready and informs the peripheral of this event by means of the DACC signal SAQ20 A maskable interrupt can be masked out using software whereas the non maskable interrupt cannot be masked out Also a non maskable interrupt has greater priority than a maskable interrupt SAQ21 a INT Rep INT Rate main process V main process ISRep ISRartc ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 147
30. 01 mode 1 1X mode 2 p Mode set flag 1 active ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 121 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Configuration example An 8255 PPI is to be used for basic I O operations with Port A as input Port B as output Port C upper as input Port C lower as input Determine the control word 1 0 0 1 1 0 0 1 t mode set i Port C lower input Port A mode 0 Port B output Port A input Port B mode 0 Port C upper input Control word 99H SAQ22 Determine the control bytes for the following PPI configurations i Port A as input port B as input and port C as input Gi Port A as input port B as output port C upper as input and port C lower as output iii Port A as input port B as output Both with handshaking facilities iv Port A as bi directional v Port A as output and port B as input Both with handshaking and available I O bits on port C as inputs 122 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Programming the 8255 PPI The following port address will be used in the subsequent program examples Port A 284 H Port B 285 H Port C 286 H Control register 287 H Control byte H This depends on the application On the PC IBM compatible pers
31. 2 PC automatically incremented by 1 The read signal to memory is activated and the The AD 34 is contents of location 0101 are read via the data bus stored in the into the MAR of the microprocessor MAR is a memory address memory address register that can access memory register locations like the PC c PC 0102 is sent out on the address bus PC always points to the next location PC 0103 PC automatically incremented by 1 The read signal to memory is activated and the The ADy 20 is contents of location 0102 are read via the data bus stored in memory into the MAR of the microprocessor MAR is a address register memory address register that can access memory locations like the PC d MAR 2034 is sent out on the address bus PC 0103 The read signal to memory is activated and the contents of location 2034 are read via the data bus into the Al accumulator of the microprocessor PC 0103 Ready for next instruction 56 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE The four machine cycles for MOV AL 2034 are shown below Figure 8 The execution of an instruction M1 M4 are machine cycles T1 T5 are clock pulses within each machine cycle It should be noted that the number of clock pulses required varies with the complexity of the activity taking place in the machine cycle ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 57
32. BER SAVE RESULT IN LOCATION 2 This program adds and subtracts two numbers and stores the results in memory locations 142 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland ANSWERS TO SAQs prog 13_pas Get values for mem1 and memz2 via KBD store EE in mem3 store DD in mem3 message to screen This program reads two numbers from the keyboard If they are equal the result EEy is displayed If they are different the result DDy is displayed ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 143 Learning and Teaching Scotland ANSWERS TO SAQs prog 14_pas Get a number from the KBD mem2 EEH mem2 00H Output message to screen This program reads a number from the keyboard works out whether it is odd oreven The appropriate message is then displayed 144 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland ANSWERS TO SAQs prog 15_pas configure ports read port C send this data to port B Invert the data at port B This program configures port C as input and port B as output The data is read from port C and the inverse of this data is flashed at port B The process repeats indefinitely ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 145 Learning and Teaching Scotland ANSWERS TO SAQs SAQI7 program saq17 uses crt
33. CANDIDATE INFORMATION AND SUPPORT MATERIAL e Before equipment is made live circuit connections and layouts should be checked by your supervisor e If you are working in a group all members of the group should give their assent before equipment is made live e Never make changes to either circuits or mechanical layouts without isolating the circuit by switching it off and removing connections to supplies e Experimental equipment left unattended should be isolated from the supply unless it has to be left on for some special reason in which case a barrier and warning notice are required e Equipment found to be faulty in any way should be reported to your supervisor immediately and not used until it is inspected and declared safe e Be fully aware of what to do if there is an emergency in the Electronics Laboratory e Use hand tools carefully and treat them with respect as they can be dangerous when misused or faulty e Do not remove equipment tools or materials from the Electronics Laboratory without authorisation from your supervisor e Always shut down the computer before switching off the power e Always switch off the power to the computer when connecting disconnecting interface equipment 36 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE SECTION C6 Candidate notes Analogue and digital signals An analogue signal is continuousl
34. MP AL AA 136D 0105 7509 JNZ 0110 136D 0107 A00102 MOV _ AL 0201 136D 010A 3CAA CMP AL AA 136D 010C 7509 INZ 0117 136D 010E CD20 INT 20 136D 0110 B000 MOV AL 00 136D 0112 A20002 MOV 0200 AL 136D 0115 EBF7 JMP 010E 136D 0117 B000 MOV AL 0O0 lt 136D 0119 A20102 MOV 0201 AL 136D 011C EBFO JMP 010E p e 0200 136D 0200 AA 55 2 0100 Program terminated normally e 0200 136D 0200 AA 00 84 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Assembly language The process of creating programs in assembly language is similar to that used for other programming languages and is flow charted below describe the problem Problem Specification Solution Design Code in chosen language produce sub tasks and flow charts translate design into source code using text editor translate source code into object machine code check for syntax errors functionality test fix any erros and re test until fully functional No Finish documentation Each microprocessor has its own assembly language for example the 8086 assembly language is different from that of the 68000 Also the assemblers for a particular microprocessor from various software houses use the same nmemonics but have many differences For the 8086 family of microprocessors various assemblers exist such as MASM A86 NASM
35. NATIONAL QUALIFICATIONS CURRICULUM SUPPORT Design Engineering and Technology Electronics Microprocessor Systems Hardware ADVANCED HIGHER Nirmal Singh m N Acknowledgements This document is produced by Learning and Teaching Scotland as part of the National Qualifications support programme for Design Engineering and Technology First published 2003 Electronic version 2003 Learning and Teaching Scotland 2003 This publication may be reproduced in whole or in part for educational purposes by educational establishments in Scotland provided that no profit accrues at any stage CONTENTS Staff information and support material Section S1 Section S2 Section S3 Section S4 Section S5 Section S6 Section S7 Candidate Section Cl Section C2 Section C3 Section C4 Section C5 Section C6 Section C7 Section C8 Outcomes to be covered in the unit Teaching and learning advice including how to use the resource material Details of starting points based on Higher Electronics Assessment procedures showing what is to be assessed when it is to be assessed and procedures for recording results Resource requirements including course notes laboratory sheets book list audio visual aid list Electronics laboratory requirements including technical information sources components materials facilities and equipment Safety information and support material
36. O INTR B INTR B PC1 IBF B OBF B eee Bete Maclaren O TB Be cece a occ AOR B eosar PC3 INTRA INTRA PC4 ISTB A I O PES OAT IBFA I O PC6 I O ACK A PC7 I O OBFA Mode 2 provides an 8 bit bi directional bus on port A Port B is not used and handshaking is provided by port C Note that in mode 1 or mode 2 operation of the 8255 the control signals from port C can be used to interrupt the microprocessor These interrupt requests are enabled or disabled by setting or resetting the appropriate interrupt enable flip flop in the PPI The three modes of operation of the 8255 are summarised as follows ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 117 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI PAO IN OUT IN OUT o PAI IN OUT IN OUT PA2 IN OUT IN OUT lt gt PA3 IN OUT IN OUT lt gt PA4 IN OUT IN OUT e gt PA5 IN OUT IN OUT PA6 IN OUT IN OUT PA7 IN OUT IN OUT PBO IN OUT IN OUT ___ PB1 IN OUT IN OUT PB2 IN OUT IN OUT Mode 0 PB3 IN OUT IN OUT or Mode PB4 IN OUT IN OUT T lonly PB5 IN OUT IN OUT PB6 IN OUT IN OUT PB7 IN OUT IN OUT PCO IN OUT INTRB INTRB I O PC1 IN OUT IBF B OBF B VO PC2 IN OUT STBB ACKB I O PC3 IN OUT INTRA INTRA INTR A PC4 IN OUT STB A VO STB A PC5 IN OUT IBF A VO IBF A PC6 IN OUT 1 0 ACK A ACK A PC7 IN OUT VO OBF A OBF A
37. OPROCESSOR SYSTEMS HARDWARE Four bits can generate 16 different combinations earlier it was stated that 2 bits could generate 4 different combinations Therefore each hex digit may be represented by a unique 4 bit code Table 6 below shows the relationship between the decimal binary and hexadecimal number systems Table 6 Decimal binary and hex number systems Decimal Binary Hex 10 1 128 64 32 16 8 4 2 1 16 1 0 0 0 0 0 0 1 0 0 0 1 1 2 o 0 1 0 2 3 0 0 1 1 3 4 0 1 0 0 4 5 0 1 0 1 5 6 0 1 1 0 6 7 0 1 1 1 7 8 1 0 0 0 8 9 1 0 0 1 9 1 0 1 0 1 0 A 1 1 1 0 1 1 B 1 2 1 1 0 0 C 1 3 1 1 0 1 D 1 4 1 1 1 0 E 1 5 1 1 1 1 F 1 6 0 0 0 1 0 0 0 0 1 0 To convert hexadecimal numbers into binary simply replace each hex digit by its 4 bit code To convert binary numbers into hexadecimal group the bits in 4s starting from the right hand side and replace each 4 bit code by its hexadecimal symbol Note that in a string of binary digits the left hand bit is called the most significant bit MSB and the right hand bit the least significant bit LSB 42 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE SAQ 3 Convert the following binary numbers into hex a 1010 1010 b 0101 0101 c 1111 0000 d 1101 0010 e 1000 0001 SAQ 4 Con
38. Outcome 1 PC a b d Tutor comments Satisfactory Unsatisfactory Outcome 1 PC c Tutor comments Satisfactory Unsatisfactory Outcome 2 Tutor comments Satisfactory Unsatisfactory Outcome 3 PC a Tutor comments Satisfactory Unsatisfactory Outcome 3 PC b c Tutor comments Satisfactory Unsatisfactory Outcome 4 PC a Tutor comments Satisfactory Unsatisfactory Outcome 4 PC b c Tutor comments Satisfactory Unsatisfactory 14 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL SECTION S5 Resource requirements including course notes book list audio visual aid list Course notes Candidate notes on Microprocessor Systems Hardware are provided in the Candidate Support Material in this pack These should be either adopted by the centre or modified to suit the teaching approach taken and the equipment available Class tests and laboratory sheets Incomplete class test and assignment sheets covering the performance criteria for outcomes 1 and 2 are available in the NABs Almost fifty percent of the performance criteria of Microprocessor Systems Hardware require candidates to operate and test the PPI in conjunction with software and hardware Laboratory sheets for outcomes 3 and 4 covering th
39. R SYSTEMS HARDWARE Program 3 DEBUG version e 0200 136D 0200 AA 55 Data before run r AX 0000 BX 0000 CX 0000 DX 0000 SP FFEE DS 136D ES 136D SS 136D CS 136D IP 0100 u 0100 0122 136D 0100 A00002 MOV AL 0200 136D 0103 22060102 AND AL 0201 136D 0107 88C3 MOV BL AL 136D 0109 A00002 MOV AL 0200 136D 010C 0A060102 OR AL 0201 136D 0110 88C7 MOV BH AL 136D 0112 A00002 MOV AL 0200 136D 0115 240F AND AL OF 136D 0117 A20002 MOV 0200 AL 136D 011A 0A060102 OR AL 0201 136D 011E A20102 MOV 0201 AL 136D 0121 CD20 INT 20 2 0100 Program terminated normally e 0200 136D 0200 OA SF Data after run t Sample trace AX 00FF BX FFOO CX 0000 DX 0000 SP FFEE DS 136D ES 136D SS 136D CS 136D IP 0110 136D 0110 88C7 MOV BH AL t AX 00FF BX FF00 CX 0000 DX 0000 SP FFEE DS 136D ES 136D SS 136D CS 136D IP 0112 136D 0112 A00002 MOV AL 0200 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 83 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Program 4 DEBUG version u 0100 136D 0100 A00002 MOV AL 0200 136D 0103 3CAA CMP AL AA 136D 0105 7502 JNZ 0109 136D 0107 CD20 INT 20 136D 0109 B000 MOV AL 00 136D 010B A20002 MOV 0200 AL 136D 010E EBF7 JMP 0107 e 0200 136D 0200 55 g 0100 Program terminated normally e 0200 136D 0200 00 Note JNZ rather than JNE Program 5 DEBUG version u 0100 0120 136D 0100 A00002 MOV __ AL 0200 136D 0103 3CAA C
40. Scotland TUTORIAL QUESTIONS WITHOUT ANSWERS 2 A4Kx 1 byte EPROM chip has 12 address lines and 8 data lines When blank each cell is in the logic 1 state Only blank EPROMs are shipped to customers by the manufacturer Write a program to test for blank 4K x 1 byte EPROMs using the set up below PC1 Red LED Error PORT C PCO Green LED Blank OK Use a 16 bit register in the microprocessor to track the EPROM addresses 136 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland TUTORIAL QUESTIONS WITHOUT ANSWERS 3 A DAC digital to analogue convertor is to be used in a microprocessor system to generate various waveforms In the set up shown below when PCO 0 a ramp waveform is desired with PCO 1 a triangular waveform should appear PORT B WAVEFORM PORTC K OV Write a program which generates a ramp triangular wave in accordance with PCO over the full range of the DAC D Write a program that allows a microprocessor to send data to a peripheral device using handshaking Output Device ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 137 Learning and Teaching Scotland TUTORIAL QUESTIONS WITHOUT ANSWERS 5 The temperature of an industrial process is measured via an ADC analogue to digital convertor If the temperature is within limits defined by CO and 80 then an enable signal is generated on PCO If the temperat
41. allocated to I O activities or learnt by the user The downside is that memory mapped I O reduces the available memory for programs Some systems used I O mapped input output ports sometimes called isolated I O In this case ports are accessed using special signals and instructions The port addresses are shown on an I O map The advantage of this method is that the I O devices do not eat into the program memory address space Instructions for accessing I O mapped ports may take form below Reading a port IN AL PORTC This means copy the contents of PORT C into the accumulator AL Writing to a port OUT PORTB AL This means copy the information in the accumulator AL to PORT B ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 59 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Memory implementation The 64k memory of a microprocessor system can be easily implemented using standard byte wide memory chips of the type shown below Figure 10 Block diagram of a simple RAM chip Address Lines Random Access Chip select Memory Data Lines CS OE WR When an address is applied and the CS input goes low a memory location is selected in the chip When OE goes low the contents of the selected location are placed on the data bus When WR goes low the data bus information is copied into the selected location When the chip is not selected its output lines are disconnected from the da
42. begin asm call config cofigure ports subroutine monitor call sensors sensors state routine cmp al 00 je alarm both sensors inactive cmp al 08 je pump low level sensor active cmp al 10 je alarm only high level sensor active mov al 00 mov dx portb both sensors active out dx al pump amp alarm OFF jmp monitor alarm mov al 02 mov dx portb out dx al alarm ON jmp monitor pump mov al 01 mov dx portb out dx al pump ON jmp monitor ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 131 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Sub Programs config mov dx ctrlreg configure ports mov al ctrlbyte subroutine out dx al ret sensors mov dx portc masking subroutine in al dx and al 18 ret al contains result e end end 132 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI d Coding using Pascal procedure program ports3a uses crt const porta 284 equates portb porta 1 portc porta 2 ctrlreg porta 3 ctrlbyte 89 var mem1 byte variable procedure config begin asm mov dx ctrlreg mov al ctrlbyte out dx al end end procedure Sensors begin asm mov dx portc in al dx and al 18 mov meml al result in me
43. bits wide and synchronises the events within the system SAQ10 2 65 536 64k SAQI1 ROM stands for Read Only Memory hence the WR write signal is not required SAQ12 The 8086 has a 16 bit data bus and 20 bit address bus The 20 bit address is formed by a segment register and the PC IP register The contents of the segment register are multiplied by 16 and to this result is added the contents of the PC The PC contents are sometimes referred to as the OFFSET address Formation of the 20 bit address is illustrated below 15 0 20 bit address 8086 address generation 140 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland ANSWERS TO SAQs SAQ13 a AAy z 0 b AAy z 0 c 00 z 1 d AE z 0 c 0 SAQ14 Shift Right hy lsc ne na E Rotate Right SAQ15 Program Element Contents hex prog6 asm al FE prog7 asm al OA bh OF mem1 14 mem2 OA prog8 asm meml 00 mem2 FF mem3 FF prog9 asm al BO num BA al BA progl0 asm The program configures explain operation of port A and B as output program and port C as input Data is taken ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 141 Learning and Teaching Scotland ANSWERS TO SAQs SAQ16 prog 12_pas PUT 2ND NUMBER IN LOCATION 1 GET THE 1ST NUMBER ADD TO LOCATION 1 SUBTRACT THE 2ND NUMBER FROM 1ST NUM
44. ble on request They are useful as visual aids on the walls of the electronics microprocessor teaching laboratory as they create an appropriate professional atmosphere and over a period of time act as a constant reminder to candidates Data booklets Technological Studies Data Booklet Hodder Gibson 2A Christie Street Paisley PA INB Data sheets on microprocessor and support devices These may be obtained via the Internet from the manufacturers websites or they may be provided by the teaching section A sample is provided with the support notes Electrical formulae booklet These should be either constructed by the candidate or provided by the teaching section Their main advantage is that they are tailored to fit the courses on offer 16 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL SECTION S6 Electronics laboratory requirements including technical information sources components materials facilities and equipment Technical information sources It should be noted that developments in electronics communications and computing continue to offer tremendous opportunities for the dissemination and retrieval of information Examples at the time of writing are the internet CD ROM and online component distributors catalogues and websites for manufacturers suppliers and providers of educational material All of these and similar pote
45. bolic notation Comment DEBUG Syntax AND AND AL 06 ALAL AND 06 immediate data OR AND AL BL ALAL AND BL register data XOR OR AL 0A ALAL AND 0A OR AL AH AL lt AL OR AH XOR AL 0200 ALAL XOR 0200 memory data XOR AL AL ALAL XOR AL Bit wise logical operation is carried out on the corresponding bits of bytes specified by the destination and source parts of the instruction and the result is stored in the destination SHL SHL AL I shift logical left the contents of AL by 1 SHL AL CL shift logical left the contents of AL by the value held in CL SHR SHR AL 1 shift logical right the contents of AL by 1 SHR AL CL shift logical right the contents of AL by the value held in CL Test compare and branch instruction These instructions allow decisions to be made regarding the state of the microprocessor or process just completed Function Example using DEBUG Comment syntax Compare CMP AL 06 AL 06 immediate CMP AL BL AL BL register CMP AL 2000 AL 0200 memory ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 77 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE In the sample instructions shown above the contents of AL are compared with the source element data If the two numbers are equal the z flag is set toa 1 The contents of the AL and the source component are not altered Jump if Equal JE O11F Branc
46. cycle e Output write cycle All instructions start with the op code fetch cycle operations that follow depend on the nature of the instruction The general instruction cycle fetch execute cycle consists of about four operations or machine cycles 54 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE a Fetch op code b Fetch address low byte AD or data byte c Fetch address high byte ADy if applicable d Complete the instruction execution via read write cycle Consider the execution of the instruction MOV AL 2034 Copy the contents of location 2034 into the accumulator AL Assume that the instruction is stored as Memory location hex Memory contents hex 0100 A9 0101 34 0102 20 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 55 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE The following sequence of events takes place Step Action Comment a PC 0100 is sent out on the address bus PC is initialised PC 0101 PC automatically incremented by 1 The read signal to memory is activated and the The op code is contents of location 0100 are read via the data bus fetched into the instruction register IR of the microprocessor b PC 0101 is sent out on the address bus PC always points to the next location PC 010
47. d and data processing is widely available at reasonable cost and is generally selected by centres to conform with their local policy These may find application in the creation of reports and the analysis of results In addition however circuit simulation and drawing software may also be used but is less widely available and more difficult to locate in a form that is cost effective for the teaching laboratory To meet these criteria the software must be easy to use without extensive training and be available at low cost with multiple copies site licensed Several products on the market have stood the test of time and are favoured for use in colleges and schools they are listed below 22 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Invent crocodile clips simple simulation of electronics and mechanics Web address WWW crocodile clips com education v3 htm E mail sales crocodile clips com Telephone 0131 226 1511 Fax 0131 226 1522 Address Crocodile Clips 11 Randolph Place Edinburgh EH3 7TA Electronics Workbench circuit simulation and testing Web address http www adeptscience co uk E mail info adeptscience co uk Telephone 01462 480055 Fax 01462 480213 Address Adept Science plc 6 Business Centre West Avenue One Letchworth Herts SG6 2HB SmartDraw drawing of diagrams and plans with associated symbol libraries Web address
48. d favour in a number of centres and has proved its worth for several teams of teaching engineers Trunking with 13 amp socket outlets should be fitted around the walls at a convenient height above the wide tables Each candidate should have available a 2 metre run of surface and at least four 13 amp socket outlets This is necessary to allow adequate working surface for test equipment circuits components and papers Eye level shelving around the walls above the power socket trunking can also be useful for test instruments and general storage 20 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL The socket outlets should be protected by a suitable device such as an earth leakage circuit breaker and a central safety switch with key lock The design and installation of such facilities should be undertaken by a specialist since these constitute important safety features The central tables are used for written work and group teaching Suitable strong moveable chairs such as those found in hotel conference rooms should be provided in adequate numbers to allow seating around the wall tables or in the centre but not both Excessive furniture and narrow spaces between tables in the laboratory can be a safety hazard and should be avoided The room should be brightly lit and well ventilated Equipment In the electronics microprocessor laboratory each ca
49. d test the operation of the PPI device to laboratory meet a given specification assignment sheets 4 a Outcome 4 laboratory assignment questions to Completed correctly explain the operation of a functional laboratory assembly language program assignment sheets b Outcome 4 laboratory assignment to modify Completed c and test an assembly language program to laboratory meet a specified operational change assignment sheets 8 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL The timing and duration of assessments It is recommended that the microprocessor systems hardware be taught as a sequence of blocks with a theory block followed by a practical block At the end of each block there should be an assignment that concludes the work on the block while providing evidence for the performance criteria The timing of these assignments is dependent on the candidate s understanding of the relevant block these should be selected with that as the main constraint The recommended sequence for teaching the unit as follows outcomes 1 3 2 and 4 Outcome 1 assessment is in two parts The first part is a written class test which should be delivered after the teaching of the whole of Outcome 1 The second part is a written assignment covering PC c which should be given after the teaching of this topic As an integral part of the teaching
50. data to port A and the output buffer full signal OBF A goes low to signal to the output device that data is available The output device monitors the output buffer signal for a logic O that is the data available signal The output device signals the acceptance of data by making the acknowledge signal ACK A PC6 low This sets signal OBF A PC 7 to a logic 1 Port B operates in a similar manner using its own handshake signals 120 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Configuring the 8255 PPI Before the 8255 ports can be used for data transfer the mode of operation of the device must be set This is achieved by writing a control word byte into the control register The modes for port A and port B can be separately defined while port C is divided into two parts as required by port A and port B definitions The format of the control word for mode selection and port configuration is shown below Figure 34 Mode definition format Control word b7 b6 b5 b4 b3 b2 b1 bO GROUP B Port C lower 1 input gt 0 output Port B P 1 input 0 output Mode Selection P 0 mode 0 1 mode 1 GROUP A p gt Port C upper 1 input 0 output Port A 1 input 0 output P Mode selection 00 mode 0
51. data transfer is used when the microprocessor and peripheral devices are operating at the same speed using a common clock as shown below Figure 19 Synchronous parallel data transfer Micro O Peripheral processor Interface Device Common Clock A continuous stream of data bytes is transferred from one system to another under the control of a common clock pulse Peripheral devices in this situation are more likely to be electronic circuits or electronic equipment rather than electromechanical devices such as printers or process control apparatus 104 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland DATA TRANSFER TECHNIQUES Asynchronous parallel data transfer In general peripheral devices connected to a microprocessor system operate at speeds much lower than that of the microprocessor itself To enable successful data transfer between the two systems asynchronous communication is used Asynchronous data transfer involves the use of two handshake control signals data available DAV and data accepted DACC to enable the data to transfer with integrity between the two systems Figure 20 Asynchronous data transfer Microprocessor I O Peripheral Interface Device In asynchronous data communication data is transferred to or received from the peripheral device when it is ready The above diagram shows data transfer to the peripheral device The process is carried
52. e Free technical helpline 0133 2799123 Address Farnell Electronic Components Canal Road Leeds LS12 2TU Access should be provided for candidates to one or more of the above component distributors catalogues in paper CD ROM or online form Selected data books reference books and specialist texts should also be provided from those offered by the above sources There are so many good items on offer that it is impossible to recommend a definitive list that is largely a matter of local preference Choices should be based on staff expertise the teaching and learning approaches used and the budget available Since many of the smaller specialised texts are low cost it should be possible to provide several reference copies for use in the electronics laboratory Many manufacturers of electronic components have websites These may be located by a net search using the manufacturer s name Once into the website it is often possible to locate technical data application information and in some situations design tutorials Components The electronics microprocessor laboratory should offer access to component stocks as a standard facility This is for the benefit of both staff and candidates who will require access to components for demonstrations experimentation and for case study and project work The stock however has to be managed and controlled if the quality of the facility is to be sustained The approach taken to this is a
53. e In addition other methods may be identified such as Computer Based Training if the centre has such a facility The outcome of this should be a teaching methodology that pervades the course and sets it apart from others 4 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Microprocessor Systems Hardware unit delivery Main topics Delivery suggested Outcome 1 Microprocessor based system block diagram Semiconductor memories Memory organisation Internal architecture of a microprocessor Instruction cycle Explain the theory and technology tutorial examples Explain the theory and technology tutorial examples Explain the theory supplement with examples Describe the generalised 8 bit architecture and relate it to a 16 bit microprocessor e g Intel 8086 Explain theory of a fetch execute cycle Outcome 2 Synchronous and asynchronous data transfers Maskable and non maskable interrupts Priority of interrupts Explain the theory tutorial examples Practical exercises Explain the theory tutorial examples Explain the theory tutorial examples Outcome 3 Programmable peripheral interface PPI chip and its control register Simple assembly language programs Input output data transfer programs Literature searches data sheets explain technology benefits and use Explain theory practical ex
54. e range statements are available in the NABs These NABs should be either adopted by the centre or modified with SQA approval to suit the teaching approach taken and the equipment available Further examples questions may be added to the list provided these meet the unit s performance criteria Book list Coffron J W Programming the 8086 8088 Sybex ISBN 0 89588 120 9 Crisp John Introduction to Microprocessors Newnes ISBN 0 7506 3787 0 Ditch W Microelectronic Systems Part One Arnold ISBN 0 340 58486 6 Ditch W Microelectronic Systems Part Two Arnold ISBN 0 340 61442 0 Vears R Microelectronics Systems Newnes ISBN 0 7506 2819 7 ESM Electronics Service Manual Wimborne Publishing Ltd Allen House East Borough Wimborne Dorset BH21 1PF Tel 01202 881749 Fax 01202 641692 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 15 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Audio visual aids The electronics microprocessor teaching laboratory should have prominently displayed an electrical safety notice These are available from a variety of electrical and electronic wholesale outlets and distributors and are relatively inexpensive Component manufacturers and distributors offer wall charts and posters showing many aspects of electronics These vary from resistor colour codes to product processing details and application advertisements They are generally free and availa
55. e of interest then the unwanted bits are set to zero or masked out This is achieved by choosing a logical operation and a mask byte The bits to be masked out zeroed are ANDed with a 0 and the bits to be retained are ANDed with a 1 Example 1 To monitor the LSB of a byte then mask the byte with 0000 0001 using the AND operation as shown below original byte XXXX XXXX mask 0000 0001 result of AND 0000 000x This means the resultant byte can have the values OOh if bit 0 0 or O1h if bit O 1 Hence decisions may be based on the state of bit 0 Example 2 In a particular program decisions need to be made dependent on the states of the MSB and LSB in a byte How is this achieved The MSB and LSB need to be masked in and all other bits in the byte set to zero as shown below original byte XXXX XXXX mask 1000 0001 AND result x000 000x The result will have one of the following values 0000 0000 00h if MSB LSB 0 0000 0001 01h if MSB 0 LSB 1 1000 0000 80h if MSB 1 LSB 0 1000 0001 81h if MSB LSB 1 Decisions can now be based on these values that is 0Oh Olh 80h or 81h 100 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING Setting bits in a byte To set a bit in a byte simply OR the necessary bit with a 1 and the rest with zeros Example 3 Set bit 6 in a byte toa 1 ori
56. eaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Program 5 mov al 0200 cmp al aa jne branchl mov al 0201 cmp al aa jne branch2 branch3 int 20h branchl mov al 00 mov 0200 00 jmp branch3 branch2 mov al 00 mov 0201 al jmp branch3 Question Draw a flowchart for the above program and hence state its purpose Answer Get first number Get second number store 00 in loc 0200 store 00 in loc 0201 If the numbers in memory are aah they remain untouched If the numbers in memory are not aah they are placed by 00 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 81 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Actual DEBUG programs for program 1 to 5 are now presented Program 1 DEBUG version u 100 136D 0100 BOAA MOV AL AA 136D 0102 A20002 MOV 0200 AL 136D 0105 B055 MOV AL 55 136D 0107 A20102 en a AL 136D 010A CD20 Segment Machine Code Mnemonic Instructions Address ae Program 2 DEBUG version e 0200 136D 0200 AA 55 Data in memory IP 0200 u 0100 136D 0100 A00002 MOV AL 0200 136D 0103 8A260102 MOV AH 0201 136D 0107 88260002 MOV 0200 AH 136D 010B A20102 MOV 0201 AL 136D 010E CD20 INT 20 g 0100 Execute program Program terminated normally e 0200 136D 0200 55 AA Data after program execution 82 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSO
57. el data transfer techniques are clearly explained b The technique of interrupts to synchronise data transfer is clearly explained c The operation of a non maskable interrupt NMI as a technique for determining the priority of an interrupting device is clearly explained ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 27 Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL Note on the range of the outcome Data transfer techniques synchronous asynchronous handshaking Evidence requirements Written and graphical evidence that the candidate can correctly explain parallel methods of data transfer and the technique of interrupting in data transfer Outcome 3 Use a programmable peripheral interface integrated circuit Performance criteria a Given the block diagram of a programmable peripheral interface PPI integrated circuit its operation is clearly explained b Using a manufacturer s data sheets a programmable peripheral interface integrated circuit configuration is designed to meet a given specification c Given suitable software and hardware a programmable peripheral interface integrated circuit is configured and tested to meet a desired specification Note on the range of the outcome The range for this outcome is fully expressed in the performance criteria Evidence requirements Written and graphical evidence that the candidate can explain the operation o
58. em voltage Maskable interrupt INTR Common peripheral devices such as the keyboard disk drive s printer clock and external hardware devices use maskable interrupts Before the 8086 microprocessor will accept an interrupt on the INTR input from any I O peripheral the interrupt flag must be enabled with the STI set ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 109 Learning and Teaching Scotland DATA TRANSFER TECHNIQUES interrupt flag instruction Conversely the interrupts may be disabled using the CLI clear interrupt flag instruction which means all maskable interrupts will be ignored Since many devices can cause a maskable interrupt each device is allocated an 8 bit code 0 255 called an interrupt type The interrupt type value is passed to the microprocessor via the data bus by the interrupting device This ensures that the correct ISR is executed for the device When the INTR is activated and the interrupt flag is disabled the interrupts are ignored and the main process continues to be executed When the INTR is activated and the interrupt flag is enabled the microprocessor completes the current instruction and the following sequence of events take place The microprocessor generates an external interrupt acknowledge signal The interrupt type code is read from the system data bus The FLAGS are pushed onto the stack Further interrupts are disabled The CS and IP registers are pushed
59. emory mapped or I O mapped The interface requirements for different types of devices are different For example the interface circuit for a keyboard is different from that for a printer or stepper motor control or a PAL programmer or an ADC DAC device Designing interface circuits for individual applications requires technical expertise and can be time consuming The design may occupy several PCBs printed circuit boards absorb considerable power and may be difficult to modify To simplify the interfacing task various microprocessor manufacturers have developed programmable input output PIO devices or programmable peripheral interface PPI chips There are readily available off the shelf low cost devices which can be software configured to satisfy hundreds of different interfacing requirements ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 113 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Since the circuit is contained in a single chip the interface is reliable and uses less power than a user designed interface Additional advantages are reduced board size reduced design time and staff need not be highly skilled The PIO PPI device can be as complex as the microprocessor itself The device contains a control register or data direction registers data registers and buffers as illustrated below Figure 28 Block diagram of a PIO PPI Data Register Data ystem data bus O L
60. ercises Explain theory practical exercises Outcome 4 Microprocessor instruction sub set Basic programs Advanced programs Explain the main types of instructions Explain the operation of simple programs that use the instructions such as ADC OR and SHL Explain the operation of complex programs that use masking and input output instructions ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 5 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL SECTION S3 Details of starting points based on Higher Electronics The units in Higher Electronics have been reviewed below for starting points for the teaching of topics in Microprocessor Systems Hardware AH Relevant outcomes are identified using the Microprocessor Systems Hardware AH outcomes as the basis Outcome 1 Describe a microprocessor based system The main topics are microprocessor based systems microprocessor internal block diagram semiconductor memory memory map and instruction cycle Unit Starting point Power Supplies H None Signal Processing and Noise H Types of signals Description of a digital signal Analogue and Digital 8 bit devices and the notion of bytes and busses Interfacing H Electronics Case Study H None Outcome 2 Explain methods of input and output data transfer The main topics are synchronous and asynchro
61. erface address control and data bus interconnections Memory dynamic random access memory DRAM static random access memory SRAM programmable read only memory PROM video random access memory VRAM cache memory Memory organisation system memory map memory and dedicated input output Evidence requirements Written and graphical evidence that the candidate can correctly describe the function of each part of a microprocessor based system in terms of semiconductor memory memory organisation memory decoding the instruction cycle and system bus Outcome 2 Explain methods of input and output data transfer Performance criteria a Parallel data transfer techniques are clearly explained b The technique of interrupts to synchronise data transfer is clearly explained c The operation of a non maskable interrupt NMI as a technique for determining the priority of an interrupting device is clearly explained ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 1 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Note on the range of the outcome Data transfer techniques synchronous asynchronous handshaking Evidence requirements Written and graphical evidence that the candidate can correctly explain parallel methods of data transfer and the technique of interrupting in data transfer Outcome 3 Use a programmable peripheral interface integrated circuit
62. errupt interrupt within an interrupt mechanism is illustrated below Figure 26 Nested interrupts INTR NMI main program main program INTR handler INTR handler NMI handler Note the return from interrupt instruction in the ISR for a non maskable interrupt may or may not return to the previous process This really depends on the nature of the NMI For example if the NMI handler routine shuts the system down safely or helps the system die gracefully there is no need to return to the previous process Nested interrupts are more common with maskable interrupts Most peripheral devices communicate with the microprocessor system using maskable interrupts and may demand service simultaneously Since more than one peripheral device can interrupt the microprocessor at the same time or cause interrupts within the execution of an interrupt service routine all the peripheral devices are allocated priority according to their importance A typical maskable interrupt priority assignment may be e Real time clock highest priority e Keyboard e Com 1 e Com 2 e Hard disk e Floppy disk e LPTI lowest priority ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 111 Learning and Teaching Scotland DATA TRANSFER TECHNIQUES SAQ21 Assume maskable interrupts are enabled at all times Using diagrams show what happens when a a floppy disk interrupt is immediately followed by real time clock RTC interrupt
63. es of data Control bus The control bus provides signals to control the operation of the system This bus is rather complex being about 10 bits wide and some signals being bi directional The clock and R W signals are part of the control bus Data bus The data bus is bi directional and its size depends on the microprocessor word size The data bus carries information to and from the microprocessor for example to and from memory to and from the ports Address bus For an 8 bit microprocessor the address bus is about 16 bits The address bus is unidirectional and emanates from the microprocessor Its purpose is to select memory locations in RAM ROM and I O ports Address decoder This circuit uses the most significant bits of the address bus to select devices ROM RAM I O chips Then the address bus lower bits select the appropriate location s A bus is basically a number of wires grouped by a function For example the 8 wires carrying data information are collectively known as the data bus 48 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE The components shown on the block diagram are external to the microprocessor Hence the busses shown are usually referred to as the external or system busses SAQ 9 Describe the 3 busses in a microprocessor system and state their function SAQ 10 Two bits can produce 4 different combinations Three b
64. ete and certainly not any more than 90 minutes Outcome 3 examines a programmable peripheral interface IC You will be required to a explain its operation using a block diagram b determine the control bytes for different configurations and c test its modes of operation using software 30 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL The assessment instrument is a laboratory assignment in which you will be required to test a pre constructed interface circuit based on a PPI device using prepared software This involves using a computer with an interface card and a port monitor board or an application board with a minimum of output LEDs and switched inputs This laboratory assignment will also test your knowledge of the operation of the PPI device If necessary you should seek clarification from your lecturer teacher before you start the laboratory exercise review your progress as you proceed and submit your pro forma report for comment on completion You may prefer to work on this with a friend but you should both contribute equally as team members and submit individual reports at the end You are unlikely to be allowed to work in teams of more than two as there is not enough in the tests to occupy you fully The laboratory exercise for Outcome 3 should take about 120 minutes to complete Outcome 4 concentrates on understanding and
65. ets operation F8 Hex numbers are pre fixed by the sign Data values here The number of begins must equal the are in decimal number of ends Upper or lower case may be used The WATCH and REGISTERS windows are launched from the WINDOWS pull down menu prior to running the program They are not available in the edit mode Assembly code is enclosed by the words asm and end Labels in the asm end block start with the sign and end with Pascal stuff The writeln statement enables messages and variable memory values to be printed on the output screen writeln The value of mem1 is lt mem1 The readIn statement enables variable memory values to be entered via the keyboard using the Enter key readin mem1 92 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING program prog12_pas uses crt const x 0f EQU y 05 var meml mem2 byte initial values unknown DB begin mem1 0 mem2 0 mem1 and mem set to zero this is pascal asm moy al y mov meml al copy one of the numbers into memory moy al x cle adc meml1 al add to memory sub al y mov mem al end end Flowchart Purpose ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 93 Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING program prog13_pas uses crt va
66. f a programmable parallel interface integrated circuit Performance evidence that the candidate programmes and tests a programmable parallel interface integrated circuit Outcome 4 Modify an assembly language program Performance criteria a A given functional assembly language program is analysed and its operation is clearly explained b A specified operational change for the assembly language program is correctly designed c The specified operational change for the assembly language program is implemented and tested until fully functional 28 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL Note on the range of the outcome The range for this outcome is fully expressed in the performance criteria Evidence requirements Written and graphical evidence that the candidate can explain and modify a given assembly language program Performance evidence that the candidate can implement and test a specified modification to an assembly language program until it is functional ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 29 Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL RY FO WOT OW The assessment instruments for the outcomes The Microprocessor Systems Hardware unit covers the different concepts involved in a microprocessor based system that is system organi
67. f the instruments of assessment but it is likely that a maximum time will be allocated for the completion of each assignment It is expected however that the average candidate will complete the work within the maximum time allowed The table below indicates the recommended time allocated for each instrument of assessment Outcome Suggested time 1 90 minutes PCs a b d 2 60 minutes 3 120 minutes 4 120 minutes It should be noted that the assessment instruments for outcomes 3 and 4 are practical laboratory assignments These assignments should be an integral part of the learning process used to develop the candidate s knowledge understanding and experience of the technology They should produce assessment evidence that the candidate has reached a satisfactory achievement level as a result of the teaching and learning process Reassessment Time is allowed within units for the assessment and reassessment of outcomes Where a candidate has not attained the standard necessary to pass a particular outcome or outcomes there should be an opportunity to be reassessed Reassessment should focus on the outcome s concerned and as a general rule should be offered on a maximum of two occasions following further work on areas of difficulty Evidence from the original unit 10 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL
68. for your chosen microprocessor To improve your knowledge and understanding of the subject material you should consult manufacturers data books data sheets or application notes on the PPI Outcome 4 covers assembly language programming To prepare for this outcome you should access the internet for information and tutorials on assembly language ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 33 Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL To improve your understanding of microprocessors and assembly programming you should source information from e manufacturers catalogues data books e the internet e electronics computing magazines journals and books e your colleagues Since this unit has a substantial practical programming content you should familiarise yourself with text file creation editing saving and retrieving processes You must also pay due attention to all safety procedures set down for the practical activities of this unit particularly when interfacing devices circuits to the PC 34 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL SECTION C5 Safety guidelines for electronics microprocessor laboratory work You should read these guidelines and discuss them with your tutor to clarify their significance in your particular working environment e Enter the Elect
69. fuller discussion or analysis of it In the laboratory it is important that the focus is on microprocessor technology data transfer and assembly language programming and that other issues such as the use of computers and the installation of hardware interface and application cards do not distract the candidate s attention To this end candidates attempting this unit should be familiar with any test equipment or system software used and be able to debug compile and verify programs The assessor should distinguish between assessment difficulties resulting from a candidate s weakness in the use of test equipment or system software and a lack of understanding of microprocessor technology and theory If the candidate is weak in the use of computers or software this should be resolved by additional training followed by the repeating of the requisite tests by the candidate The conditions under which assessment takes place Arrangements documents refer to assessment being carried out under controlled conditions to ensure reliability and credibility For the purposes of internal assessment this means that assessment evidence should be compiled under supervision to ensure that it is the candidate s own work Supervision ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 11 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL may be carried out by a teacher invigilator or other responsible person for examp
70. g equ porta 3 control register address 287h ctrlbyte equ 89h porta is O P portb is O P portec is I P code code segment startup start of program instructions mov al ctrlbyte set up ports mov dx ctrlreg out dx al loopl mov dx portc label for jump statement in al dx sread portc cmp al Offh jz finish mov dx portb out dx al write to portb jmp loopl finish slabel for branch exit sint 20h end send of text 90 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING SECTION C7 Candidate notes Writing debugging and testing assembly language programs using an assembler such as MASM is a rather tedious difficult and time consuming task A more user friendly approach is to embed the assembly language program in a high level language such as PASCAL Turbo Pascal or C The use of writeln write line and readIn read line statements helps to make the program interactive user friendly and easier to test In the following pages five PASCAL programs are presented for analysis A screen shot of progl1_pas is given This program contains detailed comments Explanations of the coding and the windows that appear in screen shot are provided Program prog15_pas deals with I O ports Although this topic has not been covered in detail enough comments are provided to enable a good understanding of the code SAQ16 Thoroughly fam
71. ginal byte XXXX XXXX mask 0100 0000 OR result x1xx XXXX Only the bit that is ORed with a 1 will with certainty be a 1 The rest remain unchanged Example 4 In a control process it is necessary to set bit 7 and reset bit 6 of a data input byte Setting a bit requires the OR operation Resetting a bit requires the AND operation Therefore two steps are necessary as illustrated below data byte XXXX XXXX OR 1000 0000 bit 7 witha 1 1xxx XXXX AND 1011 1111 10xx XXXX bit 6 with an 0 Note Only bits 7 and 6 are affected all others remain unchanged Complementing bits in a byte A bit in a byte is inverted by exclusive ORing it with a 1 Example 5 Invert the last four bits in a byte original byte XXXX XXXX mask 0000 1111 XOR XXXX XXXX Using actual bits 1010 0101 AAh 0000 1111 OF h XOR 1010 1010 A5 h ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 101 Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING SAQ17 Assume load a byte into location mem1 Write a program which checks the MSB of mem1 If the MSB 1 then half the value of the byte is stored in mem2 Ignore remainder If however MSB 0 then double the value of the byte is to be stored in mem2 SAQ18 Write a program which exchanges the adjacent bits of a byte in mem1l bz be bs ba b bo b bo J be b7 ba bs
72. h to address O1FF or label if Jump if z 1 JZ O11F two numbers are equal or if z 1 These instructions follow an operation such as a compare or an arithmetic logical operation Jump if NOT Equal JNE 0100 Branch to address 0100 or label if Jump if z 0 JNZ 0100 two numbers are not equal or if z 0 These instructions follow an operation such as a compare or an arithmetic logical operation Jump in on Carry JC 0100 Branch to address 0100 or label if c 1 Jump on not Carry JNC 0200 Branch to address 0200 or label if c 0 Unconditional Jump JMP 2000 Go to address 2000 Execute sub program CALL 2000 Execute subroutine at address 2000 or label Note again The actual address is formed by multiplying CSx16 and adding the address given in these instructions Miscellaneous instructions Function Example using DEBUG Comment Syntax Clear Carry Flag CLC C 0 Set Carry Flag STC C 1 Halt INT 20 stop Return RET Last instruction in subroutine 78 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Sample programs The programs presented here are written using the DEBUG utility program of DOS The addresses given here are for the IP the segment addresses are as assumed Program 1 mov al aa mov 0200 al mov al 55 mov 0201 al int 20 Question What will be stored in locations
73. http www smart draw com E mail sales ttp co uk Telephone 01889 564601 Fax 01889 563219 Address The Thompson Partnership Lion Buildings Market Place Uttoxeter Staffs ST14 8HZ Turbo Pascal software development including embedded assembly language Web address http www borland com E mail Telephone 0800 454065 Fax 0800 454066 Address Inprise Corporation UK Ltd 8 Pavilions Ruscombe Business Park Twyford Berkshire RG10 9NN ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 23 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Microsoft Macro Assembler MASM development of assembly language programs Web address http www microsoft co uk E mail Telephone 0870 60 10 100 Fax Address Microsoft Limited Microsoft Campus Thames Valley Park Reading RG6 1WG A86 D86 Shareware Assembler Dis assembler for assembly program development is available from various websites The Debug utility a part of MS DOS may also be used for assembly language programming The support notes for the unit Microprocessor Systems Hardware will be based around the IBM compatible PC and the Intel processor 8086 and family of support devices due to the large user base 24 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL SECTION S7 Safety The safety of teaching staff and candidates worki
74. iliarise yourself with progl1_pas then study programs prog12_pas to prog 5_pas Describe the operation of each program using a flowchart and hence state its purpose It may help you to execute these programs on the computer ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 91 Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING 45005 Prompt TUARO an E Hie ES ele A File Edit Search Run Ca gile ieou ptians Window Help TEES PROGRAM PROGLI_PAS TITLE F PROGRAM Ser ALLOWS USE OF READLN WRITELN ETC PASCAL STUFF H A CONSTANT DECLARATION SIMILAR TO EQU MEM1 BYTE VARTABLE MEMORY DECLARATION INITIAL te UNKOWN VALUES ASSIGNED IN CODE AREA SIMILAR TO DB CODE AREA CP START OF ASSEMBLY LANGUAGE DX agag MOY AL H GET THE NUMBER BH Gaga SHL AL 1 DOUBLE IT CS agag MOV MEMT AL SAVE THE ANSWER IN MEM1 DS g NO ENO OF ASSEMBLY LANGUAGE ES aaa ENO OF CODE NOTE THE SP SS Gaga cH 2 4 s o o i a 0 d mla Watches 2 ne MEML 20 Ve FL Help F7 Trade F8 Step Edit Ins Add Del Delete F10 Menu Window1 has source code Reserved Window2 shows Window3 words start in the first column predefined the values of the shows the identifiers are crt byte and asm variables memory state of CPU Note semi colons are at the end of Pascal locations under registers and statements single step FLAGS Comments are enclosed in curly brack
75. ilolo lil il lt 90 All the bits of the data byte are moved one position to the left the MSB is transferred to the c and a 0 is fed into the LSB Rotate left Before x 0 0 1 1 0 0 1 1 c After 0 lt 0 1 11010 1 1 IX Rotate is a circular operation All the bits of the data byte move our position to the left The c bit moves into the LSB and the MSB is fed into the c flag SAQ12 Explain how a 20 bit address is formed by the 8086 microprocessor 72 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE SAQ13 Calculate the results of the following operations and state the value of flags shown in each case a AA AND AA Z b AAyOR AAy Z c AAyXORAAy Z d AAy ADC 044 Z C SAQ14 Illustrate the shift right and rotate right operations Before exploring the instruction set of the 8086 study the program instructions listed below and answer the questions that follow mov al Ofh copy 15 into al register cle clear carry flag adc al Olh add 01 9 to al register mov 0200h al copy the contents of al into memory location 0200h int 21h stop Q State the function of the program What hexadecimal number will be stored in location 0200h at the end of the program A The program adds two numbers in this case fh and 1h and st
76. ines Control Register address bus including chip select Timing and Control Logic To Microprocessor 1 O Interface Chip To Peripheral Device The lower order bits of the address in conjunction with a control signal are used to select the data or control registers in the PPI The data bus is used to send or receive data from the registers in the PPI chip The control bus enables I O read write cycles and allows the use of interrupts The binary pattern stored in the control register sets the mode of operation of the PPI The diagram below gives an example of how the 3 ports of a PPI may be used Each port has 8 bits and these are labelled PA7 to PAO for port A PB7 to PBO for Port B and PC7 to PCO for port C 114 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Figure 29 An example of PPI port usage PA7 PORT port A as input A PAO PB7 PORT B port B as output PBO PC7 port C PORT Pc4 upper 4 bit as output C pc3 lower 4 bits as input PCO ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 115 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI The 8255 Programmable Peripheral Interface The Intel 8255 PPI due to its relative simplicity and ease of use is a very popular device used for interfacing It contains one control register for setting the mode of operation of the PPI and three 8 bit
77. its can produce 8 different combinations Four bits can produce 16 different combinations How many different combinations can be produced by the 16 lines wires bits of the address bus ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 49 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Microprocessor internal architecture inside the microchip The block diagram of the internal architecture of a microprocessor is given below in figure 6 Figure 6 internal architecture of a microprocessor INTERNAL DATA BUS INTERNAL CONTROL BUS INTERNAL ADDRESS BUS The busses shown on this diagram are inside the microprocessor chip and in very small systems they are directly connected to the external system busses In bigger systems however these internal busses are buffered to generate the system busses For example the internal data bus is connected to 8 bi directional buffers to produce the external data bus 50 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE In the PC market reference is usually made to local and expansion busses The local bus is made up of the 3 busses data address and control that connect directly to the microprocessor and it is used to access high speed cache memory The expansion bus interfaces to the peripheral devices such as disk drives printer and keyboard and it also connects
78. ity and some form of memory for storing the incoming data processed data and software required for manipulating the data A more detailed diagram of a typical 8 bit microprocessor system comprising these components is shown below Figure 5 Microprocessor system block diagram Address Bus Output Micro 1O gt Port ea RAM Chip processor ea Input Port ner irl n Control Bus ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 47 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE The components of this block diagram are described below Block Description Microprocessor The microprocessor consists of the control unit and the ALU It is responsible for carrying out arithmetic and logical operations as well as for providing the control signals for system operation T O interface The microprocessor itself is not very useful To communicate with the outside world ports are required The ports are normally programmable and are part of the I O interface chip RAM memory RAM is read write semi conductor memory Time taken to access any memory location is the same hence the name random access memory This memory is volatile and holds the program and data in current use ROM memory ROM is also random access memory but is non volatile and Read Only This type of memory contains firmware such as the executive program which runs when a system is switched on or tabl
79. k the smoke alarm sounds because there is a fire in the next room Now you have to put the book down and you must attend to the smoke alarm interrupt An interrupt that has to be performed and cannot be ignored is called a non maskable interrupt Clearly a non maskable interrupt is more important than a maskable one and is therefore given a higher priority SAQ20 State the difference between a maskable interrupt and a non maskable interrupt Non maskable interrupts NMI The non maskable interrupt request is always recognised by the microprocessor as it cannot be masked out by software When an NMI has been issued the 8086 microprocessor completes the current instruction saves the state of the CPU registers disables maskable interrupts and passes control to the interrupt service routine as follows The FLAGS are pushed onto the stack The INTR inputs are disabled and TF is also cleared The CS register is pushed onto the stack The IP register is pushed onto the stack The IP register is loaded with the interrupt vector address offset The CS register is loaded with the interrupt vector address segment The ISR is executed from the address formed by the new CS and IP registers SON Sse ea Power fail detection circuits may be used to issue an NMI request in the event of sudden power loss This would allow the ISR to halt the system safely while the filter capacitors held their charge and sustained a working syst
80. le a workplace provider The practical assessments should take place in a microprocessor laboratory adequately equipped with the necessary hardware and software Candidates should work individually but they may be allowed to work in pairs when verifying the programs on the hardware test equipment Candidates may have access to the programmer s model of the microprocessor the instruction sub set and the data sheet of the PPI device being used It is recommended that the assessments are introduced using the following procedure e allow the candidates a few moments to read the laboratory assignment sheet e review and summarise the tasks required by the assignment e identify the equipment and facilities provided for the assignment e explain the operating conditions within the laboratory e emphasise safety practices and precautions Candidates should be encouraged to identify themselves to the assessor on completion of the assignment and before any equipment is dismantled The assessor should if possible mark the assignment and provide immediate feedback to the candidate regarding the outcome If necessary remedial action should be performed immediately by the candidate Using internal assessment evidence to contribute to course estimates The practical assessments for this unit are designed primarily for internal assessment purposes and have only limited potential to generate evidence of performance in external assessment The assess
81. le Peripheral Interface PPI Assessment In Outcome 3 for the PPI you are testing you are expected to understand and explain its operation This may involve referring to the PPI block diagram control register control byte and some assembly language code The laboratory report test questions and the practical activities are designed to match the performance criteria for the outcome Because of this you will have to reach a minimum standard in both the test questions and the practical activities to gain a pass Outcome 4 Assembly Language Programs Assessment In Outcome 4 you are expected to understand and explain the operation function of an assembly language program You will be required to make modifications to the program and ensure that it is fully functional The laboratory report test questions and the practical activities are designed to match the performance criteria for the outcome Because of this you will have to reach a minimum standard in both the test questions and the practical activities to gain a pass NOTE Your reports should have adequate information in them to convince your tutor that you have correctly tested the PPI program and that you understand the operation of the device program 32 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL SECTION C4 Candidate s guide to working on the unit Microprocessors micro contro
82. llers are used in most modern electronic equipment for example computers amplifiers alarm systems and televisions Consequently it is important that electronic technician engineers have a good grasp of the fundamentals of microprocessor based systems Outcome 1 explores the components of a microprocessor based system that is the microprocessor RAM ROM I O Interface and busses In this outcome you are required to describe in detail all the components in the system To prepare yourself for this outcome you should familiarise yourself with e number systems decimal binary and hexadecimal e logic functions AND OR NOT EOR e computer jargon bit nibble byte RAM VRAM To improve your knowledge and understanding of the subject material you should read electronics and computing magazines Outcome 2 investigates data transfer techniques The emphasis here is on parallel data transfer using interrupts Maskable and non maskable interrupts are considered as well as their priority To improve your knowledge and understanding of the subject material you should investigate how your computer communicates with the printer via the Centronics interface Outcome 3 looks at the PPI and its operation using assembly code The basic input output operation and some parallel data communication using handshaking is discussed It would be to your advantage to revise number systems logical operations and learn some assembly language instructions
83. ly a single bit A byte size memory location is made up of 8 of these cells A memory chip contains thousands of these memory locations organised in matrix format together with decoding circuitry The word line signal shown on the diagrams is simply the output from the decoding circuitry used to select a memory location consisting of 8 cells Memory Structure Characteristics Static Ram is volatile random access read write memory The memory is composed of 4 MOSFETS acting as a bistable When the bistable is set a 1 is stored and when reset a 0 is stored The contents of this memory are held as long as power remains on l WORD LINE DATAUNE Dynamic Ram is volatile random access read write memory The memory cell is a VORDEN capacitor in fact the gate source junction capacitance of the FET in the cell When the capacitor is charged data 1 when discharged T data 0 Read is destructive therefore the read operation is always followed by a write operation The charge stored in the capacitor tends to leak due to imperfections therefore dynamic RAMs need to be refreshed on a regular basis Structure based on To improve the speed of a video system VRAM DRAM chips are used in CRT display circuitry VRAM stands for Video RAM and has one port for full read and write operations with random access and another port which allows only sequential reading scanning of image True dual ported memory allowing simultaneous
84. m end end procedure alarm begin asm mov al 02 mov dx portb out dx al end end ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 133 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI procedure pump begin asm mov al 01 mov dx portb out dx al end end begin config repeat sensors if mem 00 then alarm if mem1 08 then pump if mem 10 then alarm if mem 18 then begin asm mov al 00 mov dx portb out dx al end end until keypressed end 134 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland TUTORIAL QUESTIONS WITHOUT ANSWERS SECTION C10 1 A stepper motor is to be controlled by two sensors according to the function table below S2 S1 Action 0 0 Free wheel no phases energised 0 1 Clockwise rotation 1 0 Anti clockwise rotation 1 1 Hold locked Two phases energised Connection details are stepper motor Port C PC1 S2 To turn the motor the following codes at regular time intervals need to be applied in the sequence PB3 PB2 PB1 PBO 0 0 1 1 0 1 1 0 1 1 0 0 1 0 0 1 The delay between the codes determines the speed of the motor To reverse the direction of rotation the codes are applied in reverse sequence Design a suitable program to control the stepper motor ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 135 Learning and Teaching
85. matter for the centre s organisational structure but experience suggests that one person needs to be clearly identified as having responsibility for the stock for issuing it and for reordering 18 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Below is a typical basic selection of components resistors Low cost metal film 0 25 W standard preferred values from 1 Q to 10MQ High powered resistors 2 5 W silicon coated standard available values potentiometers 150 mW carbon trimmers standard preferred values from 100Q to 1OMQ capacitors Metallised ceramic plate capacitors standard preferred values from 1 8 pF to 120 pF Resin dipped plate ceramic capacitors standard preferred values from 10 pF to 0 47 uF Radial polystyrene capacitors standard preferred values from 100 pF to 8200 pF Radial lead electrolytic capacitors standard preferred values from 1 uF to 47000 uF Axial lead electrolytic capacitors standard preferred values from 1 uF to 47000 uF diodes 1N4148 1N4001 1N5401 BZX85 range of voltages from 2 7 V to 15 V bridge rectifier W005G light emitting diodes 3 mm and 5 mm red orange and green transistors BC184L BC214L 2N3053 BFY50 TIP31A TIP32A TIP33A 2N3055E 2N2955 2N3819 2N3820 op amps uA 741 LM 324N CA3140E logic chips 74 LS
86. ments based upon written tests offer some opportunities to provide evidence for likely performance in the external assessment however these assessments cover less than 50 of the unit content It should be noted that for course estimate purposes projecting how well candidates will perform in the external assessment staff will have to consider performance across all units Staff who wish build on evidence for estimates may wish to use a question paper that could be attempted during the additional 40 hours which are an integral part of the course 12 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Advice on the recording and retention of evidence Regular meetings and informal discussions between internal verifiers and assessors facilitate good assessment practice By using this approach assessors should understand that internal assessors are matching the internal assessments with external standards All evidence in the form of laboratory results reports should be retained in case of appeals or disputes Overleaf is an example of a checklist which could also be used to record results ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 13 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Unit Number Candidate s Name Unit Title Microprocessor Systems Hardware Class Date ____ Assessor
87. ndidate should have access to the following equipment Ideally there should be one set of equipment per candidate Multimeter Dual rail power supply Signal generator Double beam oscilloscope Logic probe Computer fitted with an interface card incorporating a PPI A port monitor board or an applications board PO Be oe ae It is also helpful to have a limited range of tools available such as snipe nosed pliers wire cutters wire strippers screwdrivers The types of tools and equipment on the market are constantly changing and improving It is strongly recommended that before purchasing any items for an electronics microprocessor laboratory advice is sought from a current user experienced in this area Issues such as the cost of hand tools in relation to their quality and life expectancy with inexperienced users who may damage or remove them from the laboratory have to be given due consideration Equipment may be found which is adequate for the teaching laboratory candidate proof inexpensive and requiring little maintenance There are many suppliers of test equipment and tools but only those specialising in the educational market are likely to offer products at an ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 21 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL acceptable price Similarly these suppliers are more likely to have tools and equipment that can survive the rigours of the
88. ng in the electronics microprocessor laboratory must be the primary concern of everyone involved This has to take precedence over all other activities and be sustained against all other pressures There are many aspects to safety as follows e statutory requirements e centre procedures centre structure e staff training and behaviour e laboratory features e candidate training and behaviour It is beyond the scope of this document to provide details of all of these items which should be incorporated into a centre s safety policy Lecturers teachers must however be content that all appropriate safety measures are in place before embarking on work within the electronics laboratory Candidate training is a recurrent activity that is likely to be the direct responsibility of the lecturer teacher While this has to take place on a continuous basis as work in the laboratory proceeds it is helpful to perform specific safety training at the beginning of the course Such training might form part of the course induction as its relevance extends across all course units This is particularly important for electronics candidates as they should be encouraged to develop their own safety culture this should become a lifelong asset Lecturers teachers performing safety training for candidates may find a rich diversity of available material Of specific relevance however is a teaching package prepared by the University of Southampton Departme
89. nment This will reinforce teaching while preparing the candidate for assessment All candidates must test the operation of the PPI in different modes using prepared software The laboratory exercise should be allocated about 120 minutes including the completion of a pro forma report This should be an integrated learning and assessment activity with emphasis clearly on learning while assessment evidence is generated as a natural by product ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 9 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Outcome 4 assessment is a laboratory assignment on assembly language programming which should be delivered after the teaching of that topic As an integral part of the teaching candidates should be given opportunities to analyse and modify pre written programs similar to those likely to be encountered in the end of topic laboratory assignment This will reinforce teaching while preparing the candidate for assessment All candidates must explain prepared software Modify and test until fully functional the change applied to the given program The laboratory exercise should be allocated about 120 minutes including the completion of a pro forma report This should be an integrated learning and assessment activity with emphasis clearly on learning while assessment evidence is generated as a natural by product In principle there are no time limits for the completion o
90. nous data transfers maskable and non maskable interrupts and the priority of an interrupt Unit Starting point Power Supplies H None Signal Processing and Noise H None Analogue and Digital Interfacing H Data communication techniques Electronics Case Study H None 6 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Outcome 3 Use a programmable peripheral interface integrated circuit The main topics are PPI block diagram PPI mode of operation control byte and testing the operation of the device in different configurations Unit Starting point Power Supplies H None Signal Processing and Noise H None Analogue and Digital Interfacing H Data communication techniques Parallel data transfers Electronics Case Study H None Outcome 4 Modify an assembly language program The main topics are microprocessor instruction sub set simple programs based on processes and complex programs based on decisions masking and input output instructions Unit Starting point Power Supplies H None Signal Processing and Noise H None Analogue and Digital None Interfacing H Electronics Case Study H None ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 7 Learning and Teaching Sc
91. nt of Electrical Engineering and Teaching Support and Media Services The package was prepared in association with and financially supported by the Health and Safety Executive It consists of ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 25 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL e ahandbook Safety Handbook for Undergraduate Electrical Teaching Laboratories e a video programme Not to Lay Blame e a booklet Tutor s Guide The pack is targeted at the first year undergraduate level and works well with other candidates at similar levels The handbook is very comprehensive and sufficiently inexpensive to be bought in quantity and given to candidates for everyday use It is well presented using text and cartoons The video dramatises issues associated with electrical electronics laboratory work using a style and characters likely to appeal to the majority of candidates The Tutor s Guide booklet rounds the package off by giving guidance on the use of the video and handbook In addition it contains Safety Rules for Electrical Laboratories and a comprehensive list of references to enable further reading should you wish it At the time of writing the distribution of the package was the subject of discussions To find out the current situation contact Maggie Bond Department of Electrical Engineering University of Southampton SO17 1BJ Tel 01703 595164 E mail M A Bond sot
92. ntial future products originate from electronics technology Accordingly candidates should be encouraged to use them and to explore and take advantage of such technological products as they emerge A culture of using the technology to its limits should be encouraged There are numerous sources of technical information on electronics other than the traditional library books These sources however are only helpful if they are both accessible and relevant The following has been refined through use and experience but inevitably will be superseded by better methods as the technology advances and they become available Component distributors catalogues MPS Maplin Website http www maplin co uk E mail lt recipient gt maplin co uk Telephone Customer services 01702 554002 Telephone Free technical helpline 01702 556001 Address Maplin MPS Freepost SMU 94 PO Box 777 Rayleigh Essex SS6 8LU RS Website http rswww com E mail http rswww com Telephone 01536 201201 Telephone Free technical helpline 01536 402888 Address RS Components Ltd P O Box 99 Corby Northants NN17 9RS ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 17 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Farnell Website http www farnell co uk E mail Enquiries farnell com Telephone Customer services 0113 2636311 Telephon
93. oltage pulse is applied to Vcg the floating gate acquires a charge to store logic 0 Electrical erasable PROMS are sometimes referred to as electrically alterable ROMS Cache memory is a block of high speed SRAM placed between the microprocessor and the bulk of the main semiconductor memory The cache controller keeps the cache filled with program instructions and data which are most likely to be used by the processor A cache hit occurs if the required data instruction for the microprocessor is in the cache otherwise there is a cache miss A typical cache is about 512k Primary cache is inside the processor and secondary cache is external 64 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Memory devices A typical EPROM device The block diagram of a 27C64 EPROM having a capacity of 64k bits organised as 8k x 8bits is shown in figure 12 and its pin out diagram in figure 13 The block diagram shows that the memory is arranged in a matrix and the internal decoding circuitry is split into an X decoder and a Y decoder Figure 12 EPROM block diagram D7 D6 D5 D4 D3 D2 D1 DO Output control ln al Output buffers Y Decoder X Memory Matrix Decoder 8K x 8 bits ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 65 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE This EPROM has e 13 add
94. omes 1000 1001 80H assume x to be zero b Flowchart configure ports read portA write port B 124 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI c Coding using PASCAL shell program ports1 uses crt const porta 284 equates portb porta 1 porte porta 2 ctrlreg porta 3 ctrlbyte 89 begin asm mov dx ctrlreg configure ports mov al ctrlbyte out dx al loop mov dx portc in al dx read port C mov dx portb out dx al write port B jmp loop repeat end end ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 125 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Example ports 2 Write a program to flash the LEDs connected to port B until port C becomes FFH a Control word for port B as output and port C as input 100 x 1002 89H assuming X 0 b Flowchart ES Vaal ae ports f read port C E gt no er ea load counter 1 load counter 2 decerement counter 2 counter 2 0 Yes decerement counter 1 counter 1 0 126 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI c Coding program ports2 uses crt const porta 284 equates portb porta 1 porte porta
95. on ac uk 26 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland CANDIDATE INFORMATION AND SUPPORT MATERIAL SECTION Cl Outcomes to be covered in the unit Outcome 1 Describe a microprocessor based system Performance criteria a Given the block diagram of a microprocessor based system the function of each block is clearly described b Describe the internal architecture of a microprocessor c Semiconductor memory memory organisation and memory decoding techniques used in microprocessor systems are clearly explained d The basic instruction cycle and system bus functions are clearly explained Note on the range of the outcome Microprocessor based system memory devices microprocessor input output interface address control and data bus interconnections Memory dynamic random access memory DRAM static random access memory SRAM programmable read only memory PROM video random access memory VRAM cache memory Memory organisation system memory map memory and dedicated input output Evidence requirements Written and graphical evidence that the candidate can correctly describe the function of each part of a microprocessor based system in terms of semiconductor memory memory organisation memory decoding the instruction cycle and system bus Outcome 2 Explain methods of input and output data transfer Performance criteria a Parall
96. onal computer the ports are I O mapped hence specialised instructions are used to read and write to the ports The port address is held in the DX register before a read or write instruction is issued IN AL DX Copies the data from the port addressed by DX into the AL register This is the read operation OUT Dx AL Copies the data in the AL register to the port addressed by the DX register This is the write operation Naturally when using the OUT instruction AL must be pre loaded with the necessary data Before the ports can be used for I O data transfer the PPI mode of operation must be set This is achieved by writing a binary pattern control byte into the control register The following code configures ports A and B as output and port C as input MOV AL 89H Load the control byte into AL MOV DX 287H Load the DX register with the control register address OUT DX AL Store the control byte in the control register These three lines of code allow the port to be configured and are usually used only once at the beginning of a program Some sample I O programs are now presented ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 123 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Example ports 1 Write a program which reads port C and transfers its data to port B The program is to repeat indefinitely Solution a Control word required 100 x 1001 This bec
97. onto the stack The IP register is loaded with the appropriate interrupt vector address OFFSET 7 The CS register is loaded with the appropriate interrupt vector address segment 8 The ISR is executed from the address formed by the new CS and IP registers Dy Soe Sa Note the interrupt type number allows the correct addresses for the ISR to be loaded into the IP and CS registers for a particular device Return from interrupt When the last instruction return from interrupt IRET of the ISR is executed the pushed registers FLAGS CS and IP are popped off the stack in the reverse order This returns the microprocessor execution to the prior process Reset input When the reset input is asserted the microprocessor restarts in an orderly fashion The process is similar to an NMI but the previous state of the microprocessor is not saved Interrupt priority Assume two events occur together for example a fire alarm and a telephone call which of these would demand urgent attention Naturally it would be 110 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland DATA TRANSFER TECHNIQUES the fire alarm as that is more critical than the telephone call Similarly in a microprocessor system an NMI interrupt has higher priority than an INTR interrupt In fact a non maskable interrupt can interrupt a maskable interrupt handler routine but the reverse is not possible The nested int
98. ores the answer in memory location 0200h 10h will be stored in memory location 0200h at the end of the program The instruction set is now explained This will enable a greater understanding of the above program Instruction set The 8086 instruction set is rather large so only a sub set of its instructions will be considered The instructions may be grouped into three main categories for convenience e data transfer e arithmetic and logical operations e test and branch operations ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 73 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Each type of instruction can have several different forms addressing modes The general format of the instruction is Operation code Operand or in more detail Operation code destination of data Data transfer instructions source of data These instructions move or rather copy the contents of a source of data into the destination of the data The general format of this instruction is mov destination source Common examples using the mnemonic instruction format are shown below The exact format depends on the syntax of the assembler being used Note all addresses given here are OFFSET addresses The actual address is formed by combining this address with a segment register as explained earlier Function Example using Symbolic Comment DEBUG syntax Notation Data to regi
99. otland STAFF INFORMATION AND SUPPORT MATERIAL SECTION S4 Assessment procedures showing what is to be assessed when it is to be assessed and methods of recording results Using the instrument of assessment The Microprocessor Systems Hardware unit is assessed using only five instruments of assessment Two class tests one written assignment and two laboratory reports assess all of the performance criteria The laboratory assignments include test questions that ensure all performance criteria are assessed The following table shows how assessment tasks are related to their outcome and performance criteria It also lists the evidence that should be collected Outcome PC Assessment task Evidence to be collected 1 a Outcome 1 test paper comprising structured Completed test b questions on the microprocessor block sheets d diagram internal architecture and fetch execute cycle c Outcome 1 written assignment covering Completed semiconductor memories memory map assignment sheets address decoding and I O addressing 2 a Outcome 2 test paper with structured Completed test b questions on parallel data transfer techniques sheets c interrupts and priority of interrupts 3 a Outcome 3 laboratory assignment questions to Completed correctly explain the operation of a PPI chip laboratory assignment sheets b Outcome 3 laboratory assignment to configure Completed c an
100. parallel ports The internal block diagram of the 8255 is given below Figure 30 Block diagram of the 8255 PPI The internal block diagram shows that port C may be considered as two 4 bit ports PC7 to PC4 port C upper and PC3 to PCO port C lower The control register is shown in two parts Group A control bits define the mode of operation of port A and port C upper 12 I O lines Group B control bits define the operation of port B and port C lower 12 I O lines 116 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI There are three modes of operation for the 8255 1 Mode 0 basic I O 2 Mode 1 strobed I O 3 Mode 2 bi directional I O Mode 0 provides two 8 bit ports A and B and two 4 bit ports port C upper and port C lower Any port may be configured as input or output Data may be read or written to the appropriate port at any time without handshaking or latching at the input ports Mode 1 provides two 8 bit ports A and B with latching at input and output ports Port C bits become handshaking lines for ports A and B Six bits of port C are used for handshaking and control three for port A and three for port B The remaining two bits may be used as I O bits The table below shows allocation of port C bits in mode 1 control Allocation of port C bits in Mode 1 Mode 1 Ports A and B Ports A and B as Input as Output PC
101. pressed in the performance criteria Evidence requirements Written and graphical evidence that the candidate can explain and modify a given assembly language program Performance evidence that the candidate can implement and test a specified modification to an assembly language program until it is functional ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 3 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Ry Od LNY Teaching and learning advice including how to use the resource material Teaching methods In general the teaching and learning methods used are very dependent on the contents of the unit and the facilities and expertise available at the delivering centre By their very nature however the units in the Advanced Higher Electronics course suggest the following teaching methods e laboratory based learning activities e use of demonstration circuits where possible e use candidate centred circuit testing and analysis e relate essential theory to circuit applications e place components used in commercial contexts e use worked examples to illustrate software structures e use input output data transfer demonstrations with prepared software e refer to manufacturers data sheets for devices under investigation It is important that all the teachers lecturers working on the Advanced Higher Electronics course share a commitment to these methods and employ them as much as possibl
102. r mem1 mem2 mem3 byte initial values unknown DB begin writeln enter value for first number readIn mem1 writeln enter value for second number readIn mem2 pascal makes it easy to get numbers into variables memory locations asm mov al meml cmp al mem2 jnz branch mov al 0ee eeh 238d mov mem3 al jmp finish branch mov al O0dd ddh 221d mov mem3 al finish end bit of pascal stuff again writeln mem1l mem1 mem2 mem2 mem3 mem3 readIn hit any key for edit screen end 94 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING Flowchart Purpose ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 95 Learning and Teaching Scotland INTRODUCTION TO ASSEMBLY LANGUAGE PROGRAMMING program prog14_pas uses crt var mem1 mem2 byte begin writeln enter numberto be analysed readIn mem1 asm mov al meml shr al 1 shift right jc branch branch if C 1 ie LSB of number 1 mov al 0ee mov mem2 al jmp finish branch moy al 00 mov mem2 al finish end writeln If mem2 0 the number is odd writeln If mem2 0ee 238 the number is even writeln mem2 mem2 readIn end 96 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland
103. ress lines A12 to AO e 8 data lines D7 to DO e 2 power supply pins e 2 active low enable signals e 2 programming signals for normal operation V and PGM are held at 5V e 1 pin not connected pin 26 for future use A typical static RAM device The block diagram of a 6264 static RAM having a capacity of 64k bits organised as 8k x 8bits is shown in figure 14 and its pin out diagram in figure 15 The block diagram shows that the memory is arranged in a matrix and the internal decoding is again two dimensional Figure 14 Static RAM block diagram 1 O7 00 OE Control Input data ICS Logic control WR A12 Column Decoder A9 x A8 Row Memory Decoder matrix Y AO Y 66 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Figure 15 The 6264 static RAM pin out diagram The pin layout for this RAM chip shows it has e 8 bit wide data D7 to DO e 13 bit address A12 to AO e 2 power supply pins e 2 chip enable signals one active high and the other active low e 2 active low write and read enable signals WR and OE e 1 not connected pin The two devices covered are similar in capacity physical size pin layout and are microprocessor compatible that is they can be easily connected to a microprocessor ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 67 Learning and Teaching Scotland MICROPROCESSOR
104. ronics Laboratory only at agreed times e Enter the Electronics Laboratory only when you are authorised e Only work on equipment when a supervisor is present e Always avoid bulky loose or trailing clothes long loose hair heavy metal bracelets or watch straps e Do not take food or drink into the Electronics Laboratory e Avoid wet hands or clothes and clean up any liquid spillages e Beas careful for the safety of others as for yourself e Think before you act be tidy and systematic e Keep passages and work areas free of obstructions e Voltages above 120 V dc and 50 V rms are always dangerous so take extra precautions as voltages increase e Never remove earth connections and make sure that all accessible conducting parts of equipment or experiments are earthed If in doubt check for earth continuity e Multimeters and hand held probes should be of good fused design and are not recommended for dangerous levels of voltage or power e Understand the correct handling procedures for batteries capacitors inductors and other energy storage devices Always handle them carefully e Fluorescent lights can cause rotating equipment to appear stationary You should be aware of this and take precautions if necessary e Before equipment is made live all casings covers or shrouds must be in place so that no live parts can be touched with fingers ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 35 Learning and Teaching Scotland
105. s SAQ15 a Study the five MASM programs and complete the table below to indicate the contents of the listed elements after the execution of the said program b Explain the function of progl0 asm As I O ports are still to be covered sufficient comments are included to enable you to answer the question Program Element Contents hex prog6 asm al prog7 asm al bh mem1 mem2 prog8 asm mem1 mem2 mem3 prog9 asm ah num al prog1l0 asm explain operation of program ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 87 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE title prog6 asm program name model tiny maximum program size 64k dosseg snormal segment order stack default stack size 100h data constant and variable declaration x equ Oaah constant x aah y equ 55h constant y 55h code code segment Startup start of program instructions mov al x program or al y shl al 1 exit int 20h end send of text title prog7 asm model tiny dosseg stack data x equ Ofh x is a constant equal to Ofh y equ 05h _ _ y is a constant equal to 05h meml db meml1 is a memory location initial value unknown mem2 db mem2 is a memory location initial value unknown code Startup mov bh x mov bly moy al bh cle get ready for addition adc al bl mov meml al save answer moy al bh sub al bl mov mem al save answer exi
106. sation data transfer methods input output interface ICs and assembly language programming Each outcome addresses a particular theme and you will be involved with assessment activities for all of the four outcomes Outcome 1 deals with the system block diagram internal architecture of the microprocessor fetch execute cycle and memory implementation You will be asked to describe the microprocessor system block diagram and its components in a short class test You will also be given an assignment in which you will be required to explain semiconductor memories and their implementation in a microprocessor system If necessary you should seek clarification from your lecturer teacher before you start any class test or assignment review your progress as you proceed and submit your pro forma class test assignment for comment on completion The class test for Outcome 1 should take about 60 minutes to complete and the assignment for Outcome 1 should be submitted within one week of issue and certainly not any more than three weeks Outcome 2 covers data transfer techniques You will be asked to explain data transfer methods types of interrupts and interrupt priority in a class test If necessary you should seek clarification from your lecturer teacher before you start the exercise review your progress as you proceed and submit your pro forma class test for comment on completion The class test for Outcome 2 should take about 60 minutes to compl
107. sed by A 3 to Ap So the address is A AA AJA A A A A A A AJA A A A 15 14 13 12 11 10 9 8 PE RN 5 4 w p hex ols gt Ola p o o fo o lo 0 0 0 o o lo 0 0o o0 TO 0000 3FFF Similarly for chips 1 2 and 3 Chip1 A AJA AJA A A A 15 14 13 12 11 10 9 hex o ojs gt a A w N p gt 4000 TO 7FFF hex p U A a N E ojs gt a W A a N 8000 BFFF ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 61 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Chip3 A AJA AJA A A A A A A A A A A A hex 15 14 13 12 11 10 9 8 Da 2 ee U A w N p a C000 ea ee ae ed i ds SRE The address decoding diagram is shown below Figure 11 Address decoding for 16k memory chips Ay ee Ao Address bus Chip 3 Data bus Chip 2 Chip 1 Chip 0 Read Write 62 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Types of semiconductor memories used in microprocessor systems The various types of memories used in microprocessor systems are now described The description includes the cell structure which is capable of storing on
108. series TTL selected functions as appropriate 4000 series CMOS selected functions as appropriate other analogue integrated circuits NE555N timer ICM7555 timer L7805CP L7812 CP positive voltage regulators L7905CT L7812 CT negative voltage regulators other digital integrated circuits Microprocessors PPIs DACs ADCs to suit laboratory applications fuses As required for instruments switches Push button toggle slide and DIL miniature as required transformers As required lamps and bulbs Low voltage and power selection to meet requirements relays Low voltage as required connectors Terminal blocks 4 mm plugs and sockets in red black blue yellow and green ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 19 Learning and Teaching Scotland STAFF INFORMATION AND SUPPORT MATERIAL Materials Few materials are required It may be helpful to have reels of solid and stranded conductor wire in a variety of colours available Some are suggested below Wire type Colour Solid Core Wire 1 0 6 Black Blue Brown Green Red White Violet Yellow Hook Up Wire 7 0 2 Black Blue Brown Green Red White Violet Yellow Facilities The ideal electronics microprocessor teaching laboratory has office style or computer tables wide around the walls with matching narrow tables in the middle A typical plan is shown below This type of layout has foun
109. ster MOV AL 4F AL 4F Copy 0100 1111 into the AL register Register to register MOV BL AL BL amp AL Copy the contents of AL into BL Register to memory MOV 0200 AL 0200 AL Copy the contents of AL into location 0200 Memory to register MOV BH 0200 BH lt 0200 Copy the contents of location 0200 into BH Register to output OUT Dx AL DX lt AL Copy the contents of port AL to the port addressed by DX Input port to IN AL DX AL amp DX Copy the contents of register the port addressed by DX into AL 74 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Arithmetic and logical operations Arithmetic operations are add subtract multiply and divide Also available are increment and decrement Logical operations are AND OR and XOR Shift and rotate operations are shift left shift right rotate left and rotate right These instructions take the usual format The operation or process is carried out on the data numbers in the destination and source elements The result is returned in the destination element as illustrated below Figure 17 The instruction process result register memory process immediate register memory ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 75 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Arithmetic Operations
110. t end 88 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE title prog8 asm model tiny stack data mem1 db Offh mem1 is variable or memory location sinitial value ffh mem2 db 00h mem2 is variable or memory location initial value 00h mem3 db 00h mem3 is variable or memory location initial value 00h code Startup moy al meml mov mem3 al moy al mem2 mov meml al mov al mem3 mov mem al What is stored in the three memory locations now exit end title prog9 asm program name model tiny maximum program size 64k dosseg snormal segment order Stack default stack size 100h data constant and variable declaration num db Oabh num is a mem loc with known value abh code code segment Startup Sstart of program instructions mov al num program mov cl 4 shl al cl cl holds shift value mov ah al mov al num shr al cl or al ah mov num al exit int 20h end send of text ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 89 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE title progl0 asm_ program name model tiny maximum program size 64k dosseg snormal segment order stack default stack size 100h data constant and variable declaration porta equ 284h porta address 284h portb equ porta 1 portb address 285h portc equ porta 2 portc address 286h ctrlre
111. ta bus that is the lines are in the tri state or high impedance condition This facility allows the output from various devices to be connected together without causing damage SAQ 11 Which of the signals discussed above is not required by a ROM chip To implement 64k of memory using 16k memory chips as shown on the memory map of figure 9 requires 4 x 16k chips The next step is to determine how many address lines are necessary to access 16k bytes Sixteen address lines can select 64k of memory Fifteen address lines can select 32k of memory Fourteen address lines can select 16k of memory The address lines A 3 to Ay are used to select the memory locations inside the memory chips The higher address lines A 5 and A 4 are decoded to produce active low chip select signals for the 4 chips so that only one chip is enabled at any time The truth table for the decoder is shown as follows 60 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE A15 A14 CS CS chip2 CS chip1 CS chip0 chip3 Rel jojo l OlR oO ole o m m Clearly the ROM of the figure 9 is chip 0 and the top two 8k blocks are chip 3 The memory space occupied by each chip can now be determined For the ROM the chip is selected when A 5 and A are both 0 and all its memory locations are then acces
112. the microprocessor continues with the main process until an I O device interrupts it Once the interrupt has been received and accepted by the microprocessor control is transferred from the main program to the interrupt service routine ISR The address of an ISR known as a vector is usually held in an interrupt vector table The ISR performs the I O task and returns control to the main program through its last instruction Return from Interrupt IRET The interrupt mechanism is shown below Figure 24 Interrupt mechanism Interrupt main program main program IRET instruction Most microprocessors have at least two pins for hardware external interrupts as below Figure 25 Interrupt inputs for a microprocessor NMI Non maskable interrupt request Micro processor INTR Maskable interrupt request RESET The above diagram shows three inputs to a microprocessor The difference between non maskable and maskable interrupts can be readily explained using real life situations Assume that you are at home reading a book The telephone rings You may choose to continue reading the book and ignore the interrupt or you may choose to answer the telephone This is 108 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland DATA TRANSFER TECHNIQUES an example of a maskable interrupt that is an interrupt which may be ignored On the other hand as you read the boo
113. truction may be one two or three bytes long A single byte instruction consists only of the operation code op code A two byte instruction consists of the op code followed by a data byte ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 53 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE A three byte instruction consists of the op code followed by a two byte address All the instructions and data are held in memory as binary hex codes This means each instruction of a microprocessor has a unique op code binary pattern A microprocessor may have hundreds of instructions or op codes which the user can use but which are difficult to remember As an aide m moire each op code is allocated a mnemonic As an example consider the instruction MOV AL 2034 a oer Op code mnemonic operand This means copy the contents of the memory location whose address is 20344 into the Al accumulator of the microprocessor This instruction is composed of three bytes as follows Op code MOV AL A9 Address low byte AD 34 Address high byte ADy 20 This will be stored in memory starting at location say 0100y as follows Memory location hex Memory contents hex Comment 0100 A9 Op code 0101 34 ADL 0102 20 ADy The instruction cycle The execution of an instruction may involve the following operations e Op code fetch cycle e Memory read cycle e Memory write cycle e Input read
114. ults of a process just completed ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 51 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE IR instruction register The instruction register holds the op code operation code of the current instruction Decoder The decoder is a PLA which decodes the op code CU control unit The outputs of the decoder are applied to the CU which generates all the controls to complete the execution of an instruction Memory Memory is an electronic circuit sometimes called a register in which binary information may be stored retrieved and updated In a basic system memory is one byte wide There are different levels of memory in a microprocessor system The fastest memory is constructed from general purpose registers inside the microprocessor the next fastest is primary cache memory again inside the microprocessor this is followed by the secondary cache memory The main or primary or semiconductor memory RAM ROM is next and the slowest memory is backup memory magnetic media The main memory may be regarded as a large array of locations pigeon holes letter trays in which data may be stored or retrieved Each memory location has its own position in the array and is accessed via the address bus The data in the selected memory location connects to the bi directional data bus The status of the read write line determines whether the data is to be written stored
115. unit BIU and the execution unit EU The EU contains the ALU flags and general purpose registers The EU carries out all the arithmetic and logical operations All the registers in the 8086 are 16 bits wide although some can be used as two 8 bit registers The BIU controls the address data and control buses When the EU is decoding an instruction or executing instructions inside the microprocessor the BIU prefetches instructions from memory and stores them in the instruction queue for faster processing ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 69 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE The 8086 has a 16 bit data bus and 20 bit address bus The 20 bit address is formed by a segment register explained later and the PC IP register The contents of the segment register are multiplied by 16 and to this result is added the contents of the PC The PC contents are sometimes referred to as the OFFSET address Formation of the 20 bit address is illustrated below Figure 17 8086 address generation 15 0 20 bit address 8086 programmer s model The programmer s model of a microprocessor is basically a diagram showing all the registers of the microprocessor that the programmer can use The 8086 programmer s model is shown as follows 70 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE 32
116. ure is above the upper limit a cooling fan is switched on to restore the temperature to within the acceptable band Similarly if the temperature falls below the lower limit a heater is switched on Write a program to carry out the above function using the set up given below temperature PORTB KC CAD Signal Fan Heater 138 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland ANSWERS TO SAQs SECTION C11 SAQI1 SAQ2 a I111 a 1549 b 100110 b 17040 c 111 1111 c 12740 d 1001 0100 d 20419 e 1111 1111 e 10240 SAQ3 SAQ4 a AAg a 0101 0101 b 55y b 1111 1010 c FOy c 1011 1100 d D2y d 10100110 e 8ly e 0001 0000 SAQ5 SAQ6 a Fy a 810 b 7Fx b 2lio c 8Cy c 18810 d C8y d 16510 e FFy e 25510 SAQ7 SAQ8 a Oly a AAy b FFy b 004 c 7Fu c 88u d 8l d 00g e FEn e 7Fy f Olp g FFy SAQ9 In an 8 bit system The data bus is 8 bits wide and is bi directional Itis used to carry data between the microprocessor and other system components ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 139 Learning and Teaching Scotland ANSWERS TO SAQs The address bus is 16 bits wide unidirectional and emanates from the microprocessor It is used to select memory locations The control bus is complex some signals are bidirectional and some unidirectional The control bus is about 10
117. ut the above functions on a pair of signals have two inputs A microprocessor normally operates on bytes of data which means it can perform logical arithmetic operations on 8 pairs of bits simultaneously For example if the microprocessor is performing the AND operation on two bytes it takes the corresponding bits in each byte and does the logical operation on all of them simultaneously This is illustrated below using actual bytes A54 AND OFy A5 1010 0101 OF 0000 1111 AND answer in binary 0000 0101 Answer in hex 054 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 45 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE SAQ 8 Find the answers to the following operations on bytes of numbers expressed in hex a AA AND FF b AA AND 00 c 80O0R 08 d 80 AND 08 e FF AND 7F f 00OR01 g 00 EOR FF 46 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Microprocessor based system block diagram A microprocessor system takes in digital signal inputs processes them by means of software and then sends them out to other devices A simplified diagram of such a system is shown below Figure 4 Simplified microprocessor system block diagram Microprocesso Digital System Digital Inputs including Outputs Software This system must have an input interface output interface processing abil
118. vely The pump and alarm are connected to PBO and PB1 respectively Devise a suitable assembly language program to satisfy the desired requirements Solution a Analysis Sensors are connected to PC3 and PC4 of port C hence the remaining bits required to be masked out after reading port C as follows XXXX XXXX AND 0001 1000 mask byte 18H 000x x000 Possible values of port C sensors after masking 0000 0000 00H 0000 1000 08H 0001 0000 10H 0001 1000 18H ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 129 Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI These values can be used to send the appropriate codes to port B as below Port C after masking Data to port B 00 H 0000 0010 02H 08 H 0000 0001 01H 10H 0000 0010 02H 18H 0000 0000 00H b Control Word Port B is output and port C is input hence control byte 89H will be acceptable c Flowchart i configure ports i E analyse sensors i sensors 00H alarm on sensors 00H sensors 00H all off alarm on 130 ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH Learning and Teaching Scotland PROGRAMMABLE PERIPHERAL INTERFACE PPI Coding using assembly language subroutines program ports3a uses crt const porta 284 equates portb porta 1 portc porta 2 ctrlreg porta 3 ctrlbyte 89
119. vert the following hex numbers into binary a 55 b FA c BC d A6 e 10 SAQ 5 Convert the following decimal numbers into hex a 15 b 127 c 140 d 200 e 255 SAQ 6 Convert the following hex numbers into decimal a 08 b 15 c BC d A5 e FF The common number ranges used in microprocessors systems are as follows e A binary digit is called a bit e Four bits are referred to as a nibble e Fight bits are called a byte e Sixteen bits are called a word The following table gives the maximum and minimum ranges for a byte and word in the commonly used number bases ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 43 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Table 7 Common number ranges used in basic microprocessor systems Decimal Binary Hex Byte Oio 0000 000 00y to to to 25510 1111 1111 FFy Word Oio 0000 0000 0000 0000 00004 to to to 65 53510 1111 1111 1111 1111 FFFFy Two s complement representation of binary numbers This representation is used to express positive and negative numbers in a microprocessor system The MSB represents the sign of the number and the remaining bits reflect the magnitude of the number Positive numbers are expressed as normal binary with the MSB set to 0 The negative numbers are formed as follows a Write the magnitude of the negative as a positive number b Invert all the bits
120. y variable that is it can take on many different values over time as shown in figure 1 Figure 1 An analogue signal amplitude continuously y variable signal t A digital signal can only have one of two values at any time as shown in figure 2 Figure 2 A digital signal amplitude 1 5y 0 Ov t A digital signal is a two state signal and its two values 5V and OV are normally represented using the binary symbols 1 and 0 respectively 1 equates to 5V 0 equates to OV ELECTRONICS MICROPROCESSOR SYSTEMS HARDWARE AH 37 Learning and Teaching Scotland MICROPROCESSOR SYSTEMS HARDWARE Number systems One binary digit bit represents a single digital signal A digital system normally uses more than one signal and each signal is represented by a bit A digital system that uses two signals A and B can be completely represented by all the different combinations of the two digital signals as shown below in table 1 and figure 3 Figure 3 Two bit digital signal combinations Table 1 Two bit digital signal combinations ojlol gt oj joln This illustration shows how binary notation can be much more convenient than using the waveform when dealing with digital systems and signals Let us examine the denary decimal number system before delving further into the binary system The decimal number system The decimal system has a base of 10 because it uses 10 symbols 0

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