Lab2 Handout - University of Guelph
Contents
1. LDX JSR CMPB BEQ PSHD LDD LDX JSR BRA SWI char pressed is 4c CR LF 0 1100 getchar 0 X 1B terminate msg printf 0 X getnewval 14 Start Address of main program get the character from the keyboard Check if the char is an ESC jump to end of program push char on stack parameter for printf second parameter in ACC D Load Index Reg X with printf address print message on terminal repeat getting new chars end of program return to D Bug122. 7 Connector H7 located at top right of breadboard 8 Connector H8 located at top left of breadboard Table 1 provides a brief description of the signals I O Pin Usage Many I O pins of the MC9S12DG256 on the Dragon12 Plus2 board are used by on board peripherals here are examples 1 PORT A Keypad Connector Signal Name Pot Dooi E H1 PP3 PP2 PP1 PPO ie Gen Purpose I O H1 PK3 PK2 PK1 PKO S Gen Purpose I O H1 PTO PT1 PT2 PT3 2 NOT USED H2 PT4 PT5 PT6 PT7 7 NOT USED H2 PK5 PK4 Gen Purpose I O H2 PJ1 PJO i NOT USED H2 PBO PB1 PB2 PB3 PB4 0 4 Gen Purpose I O H3 PB5 PB6 PB7 5 7 Gen Purpose I O H3 PH7 PH6 PH5 PH4 4 7 Gen Purpose I O PET PE6 PES PE4 4 7 NOT USED 0 3 3 a H3 H4 PH3 PH2 PH1 PHO Port H 0 Gen Purpose I O H5 PAO PAI PA2 PA3 PA4 PA5 PA6 PA7 Port A 0 7 Gen Purpose I O Piel a ent exon ee eee H6 PAD02 PADO3 PAD04 PADOS PADO6 PADO7 Port ADO 2 7 Analog to Dig H7 PS0 PS1 PS2 PS3 PS4 PS5 PS6 PS7 Port S 0 7 Serial Comm ar papa rowan NOTUSED H8 PMO PM1 PM2 PM3 PM4 PM5 Port M 0 5 NOT USED Table 1 MCU Connectors J8 J9 Pin Assignments 0 5 4 4 0 2 PORT B Light Emmitting Diodes LEDs 3 PORT H DIP and Pushbutton Switches 4 PORT K Liquid Crystal Display LCD 5 PORT P 7 Segment Display 6 PORT AD Light Sensor Temp Sensor Trimmer Pot IMPORTANT Fortunetly it s unlikely that all on board per
3. O registers PORTA EQU 0000 offset of PORTA from REGBAS DDRA EQU 0002 offset of DDRJ from REGBAS LDX REGBAS LDAA FF Set all pines of PORTA all output STAA DDRA X set PORTA as an output port LDAA CD value to output to PORTA STAA PORTA X output the data END 3 1 2 Dragon12 Plus2 Port Allocation It should be noted that the ports on the Dragon12 Plus2 are multiplexed that is they can have one of two or more possible functions The following table provides a summary Bxtemal Signals F clk IRQ XIRQ ete Please refer to Appendix A for detailed description of the MCU connectors H1 H8 i e how to access the I O ports on the Dragon12 Plus2 Board and Appendix B for the address of some registers utilized in certain ports 3 2 Simple Interface to LED s The light emitting diode LED is one of the most often used output devices in an embedded system In many embedded systems LEDs are simply used to indicate that the system is operating properly An LED can illuminate if it is forward biased and has sufficient current flowing through it The current required to light an LED may range from a few to more than 10 mA The voltage drop across the LED when it is forward biased can range from 1 6V to more than 2 2V LED indicators are easy to interface with micro controllers All you need is enough current to drive the LED and a series resistor to absorb the voltage drop limit the current to some acceptable value The c
4. ENGGS864 Microcomputer Interfacing Lab 2 Parallel Port Programming amp General Interfacing School of Engineering University of Guelph Fall 2012 Start Date Wednesday Week 4 Due Date No Report is Required 1 Objectives The purpose of this lab is to e Develop fundamental concepts associated with programming parallel ports available on the MC68HC12 micro controller e Design and construct a system which displays the 8 bit binary ASCII code of a pressed PC keyboard on LED s e Design an equivalent software decoder to display BCD numbers on a 7 segment display 2 Introduction Data transfer between the I O device and the interface chip can proceed bit by bit serial or in multiple bits parallel Data are transferred serially in low speed devices such as modems and low speed printers Parallel data transfer is mainly used by high speed I O devices In this lab we will only be concerned with parallel I O interfacing After you become familiar with the on chip ports we are going to perform several practical experiments to learn how to interface the M68HC12 to the real world In the previous lab you became familiar with programming techniques using the assembler directives In real life the MCU deals with outside devices using its internal registers memory timer A D serial ports and I O ports Usually there is an electronic interfacing circuit between the MCU and the outside world The outside device could be input or outp
5. Output binary to har SES far GetGmaEmel Obtain a Tine of input fromthe usr SEEsA ar sscanhex Convert and ASCH hex to binary mi SEESE isedigit Checks for membership 0a FAF sE toupper Converts Tower case char to upper case SEE salphaQ Checks for membership ia zA 2 sE strlen Retms the length oF astring SEs strepy Copies a mull terminated string SEBQA___ far oui2hext Displays amp bit mmber as 2 ASCH chars SEEC ar outthex Displays 16 bit number as 4 ASCI chars SEEAO SetUserVector Setup user interrupt service routine SEEM far WriteBEByte Write a data byte to on chip EEPROM SEEAG far BraseEE Bulk erase on chip EEPROM SEEMA O far ReadMem Read data from MGSHCI2 memory map SEEAE far WriteMem Write data to MGSHCI2 memory map SEEB2 Table 5 D Bug12 Utility Routines Summary Here are a set of rules that you can follow to utilize these utility routines 1 Calling a function from assembly language is simple e First push the parameters onto the stack in the proper order loading the first or only function parameter into the D Accumulator In other words if you have two parameters or arguments then one will be passed by the D Accumulator and the other pushed onto the stack e Then call the function with a JSR instruction e The code following the JSR instruction should remove any parameters pushed onto the stack If a singl
6. Result Register 7 High Byte Baud Rate Register High Baud Rate Register Low Control Register 1 Control Register 2 Status Register 1 Status Register 2 Data Register High Data Register Low Table 4 M68HC12 Ports and Registers 8 Appendix C Evaluation Board Displays of Dragon12 Plus2 Board The Dragon12 Plus2 Board has several means to display information by the MCU12 Here are some examples 1 Light Emmitting Diodes LEDs connected to Port B 2 Seven Segment Displays connected to Port P 3 Liquid Crystal Display connected to Port K Each peripheral is connected to a specific port as demonstrated above These ports can still be used as general purpose ports if the peripherals are not used 1 If you don t use the LCD or just unplug the LCD the Port K will be available as well 2 Port B drives LEDs but if you ignore the status of the LEDs the port B can drive any other I O devices on the breadboard Please refer to the Dragon12 Plus2 Trainer User s Manual for more details LEDs Each port B line is monitored by an LED In order to turn on port B LEDs the PJ1 port J pin 1 must be programmed as output and set for logic zero 7 Segment LED multiplexing There are 4 digits of 7 Segment LEDs on the Dragon12 Plus2 board The type of the 7 Segment display on board is called common cathode in an individual digit all anodes are driven individually by an output pot and all cathodes are inter
7. e parameter is stacked a PULX or PULY instruction is one of the most efficient ways to unstack it 2 All 8 bit and 16 bit function results are returned in the D Accumulator Char values returned in the D accumulator are located in the 8 bit B Accumulator 3 Boolean function results are zero for False and non zero values for True 12 Example 1 To output a single character to the control terminal SCI i e screen you can use the int putchar int function whose Pointer Address is located at EE86 If the control SCI s transmit data register is full when the function is called putchar will wait until the transmit data register is empty before sending the character Adding the following instruction sequence in your program will output the character A to the control SCI putchar equ EE86 ldd A jsr putchar PCR The addressing mode used in the jsr instruction of this example is a form of indexed indirect addressing that uses the program counter as an index register In reality the HCS12 does not support PCR Instead the PCR mnemonic is used to instruct the assembler to calculate an offset to the address specified by the label putchar The MiniIDE software supports this syntax However if you are using an assembler that does not support program counter relative indexed addressing the following two instruction sequence can be used instead ldx putchar load the address of putchar jsr O x call the subroutine I
8. eps should be taken 1 Output 06 to Port B set PPO low and PP1 PP2 and PP3 high The number 1 is shown on the digit 3 the leftmost digit but other 3 digits are turned off Delay lms Output 5B to Port B set PP1 low and PPO PP2 and PP3 high The number 2 is shown on the digit 2 but other 3 digits are turned off Delay lms Output 4F to Port B set PP2 low and PPO PP1 and PP3 high The number 3 is shown on the digit 1 but other 3 digits are turned off Delay lms Output 66 to Port B set PP3 low and PPO PP1 and PP2 high The number 4 is shown on the digit 0 the rightmost digit but other 3 digits are turned off Delay lms Go back to step 1 11 9 Appendix D Evaluation Board Using D Bug12 Routines The D Bug12 monitor provides a few subroutines to support I O operations One can utilize these I O routines to facilitate program development The D Bugl2 currently provides access to 18 different utility routines through a table of 16 bit pointers beginning at address EE80 as shown in Table 5 This appendix will provide you with some information that will allow you to utilize internal D Bug12 routines Please refer to Page 173 Section 4 8 in your text book Using the D Bug12 Functions to Perform I O Operations for detailed examples Function Description Veo Tale AS far man SoD OO O o Cd getchar Cead komso sea putchar senda char out SCI or SC sew printf Formatted
9. f the 7 Segment display e PP3 is connected to Digit 0 of the 7 Segment display Refer to Appendix C for more details of how to utilize the 7 Segment Displays on the Dragon12 Plus2 board 4 Requirements You are required to accomplish the following for this lab 1 Use the example provided to you in Section 3 1 1 to familiarize yourself with configuring I O ports and apply the same technique to port B instead of port A 2 The user will type characters on the PC keyboard whose values will be sent to the PC s serial COM port by software on the PC The PC serial port will be connected to the serial port on the HC12 The software on board the HC12 will monitor its serial port for the 8 bit character codes and latch new codes on one of its parallel output ports Use Port B on the Dragon12 Plus2 board since this port is 4 already connected to the LEDs Please refer to a Appendix D in this handout for information on utility routines that can help you get a char from the keyboard and printing a char to the terminal b Your text book Section 4 8 page 173 for using the D Bug12 functions to perform I O operations 3 Seven Segment Software Decoder e Input a number via the PC keyboard using the Debug12 utility functions e Display the number read on Digit0 of 7 Segment display on the Dragon12 Plus2 board e Use Port P since it is connected to the 7 Segment Displays 5 Academic Misconduct The policy for this course is
10. h impedance input If a write is attempted to an input pin its value does not affect the I O pin but is stored in an internal latch When the pin becomes an output this value appears at the I O pin Data direction register bits are cleared by reset to configure I O pins as inputs So to configure a pin in a certain port as an output pin a 1 should be written to the corresponding data direction register else a 0 should be written The following example illustrates how to configure port A on the MC68HC12 3 1 1 Example of Configuring a Port Problem Write an instruction sequence to set port J as an output port and output the value CD to it Solution Since port A is bi directional we need to configure it as an output port Figure 1 shows the Port A Data Register and Data Direction Registers Notice that in the code below the label PORTA was set to 0000 which is the address of Port A data register and the label DDRA was set to 0002 which is the address of the A data direction register Address UUUU Bit7 6 5 4 3 2 1 Bito PA7 PAO On Reset 0 0 0 0 0 0 0 0 Port A Data Register PORT A Address 0002 Bit7 6 5 4 3 2 1 Bito DDRA7 DDRAO On Reset 0 0 0 0 0 0 0 0 Port A Data Direction Register DDRA 1 Associated pin is an output 0 Associated pin is an input Figure 1 Port A Data Direction Registers REGBAS EQU 0000 base address of all I
11. ipherals will be used by one application program So the I O pins on unused peripheral devices can still be used by your circuits on the breadboard For instance if you don t touch the 4x4 on board keypad the entire port A will be available to your circuits 7 Appendix B Port Registers Each port within the M68HC12 has several registers that are used to control its functionality and also give the status of the port following a read write transaction Table 2 provides a brief description of the regular I O ports and their associated registers Ports A B E K can be used for Input Output based on how the Data Direction register has been programmed Por Resistor Description Address Current Usage PORT A PORTA Data Register A 0000 Keypad L S DDRA Data Dawtion Raiter A soon o PORT B PORTB Data Register B 0001 LED ee bore pata Direction Register B 0003 PORT P PORTP Data Register P 0258 7 Seg Display EOS pone Data Daston Regier soos P PORT H PORTH Data Register H 0260 DIP Switches O bone pate Divton Regter mt S02 PES PORT E PORTE Data Register E 0008 IRQ XIRQ LO Done pate Dieton Regter e mon S PORT K PORTK Data Register K 0032 LCD POY port pata Dison Reiter soo Table 2 M68HC12 I O Ports and Associated Registers Table 3 provides a brief description of the I O ports H J that have interrupt capability Wakeup Port P is very similar to ports H a
12. ircuit in Figure 2 is often used to interface with an LED Using a 5 volt supply and assuming that the LED has a 1 7 volt drop across it a suitable resistor will limit the current to 10 mA An I O port pin of a micro controller generally does not have enough drive to supply the current So an inverter is often used as a switch to turn the LED on and off When the inverter s output is low close to OV the diode has a 2 0V voltage drop and by ohm s law 5V 2 0V Irz x Rr When setting the I x to 10mA the resistor Ry is solved to be 3002 3 3 Seven Segment Decoder Digital readouts found in electronic calculators and digital watches use LEDs Each digit of the readout is formed from seven segments each consisting of one LED that can be illuminated by digital signals A BCD VCC 68HC12 74HC04 i b al BCD Input _Seven Segment Decoder ABCD abcdefg Figure 3 Seven Segment Display to seven segment decoder is a combinational circuit that accepts a decimal digit in BCD and generates the appropriate outputs for the selection of segments that display the decimal digit In this lab you will attempt to interface the MPU to a seven segment display located on the Dragon12 Plus2 Board using software Notice that Port P is used to multiplex and enable the 4 units of 7 Segment Display e PPO is connected to Digit 3 of the 7 Segment display e PP1 is connected to Digit 2 of the 7 Segment display e PP2 is connected to Digit 1 o
13. mportant If the name of a library function is preceded by the keyword far then it is located in the expanded memory and must be called by using the call instruction Example 2 To retrieve a single character from the control terminal SCI use the int getchar void function whose pointer address is located in EE84 If an unread character is not available in the receive data register when this function is called it will wait until one is received Because the character is returned as an integer the 8 bit character is placed in accumulator B Adding the following instruction sequence in your program will read a character from the SCIO port getchar equ EE84 jsr getchar PCR Example 3 The following is a sample code for utilizing the getchar and printf utility routines Notice that there are two org statements The first org statement is to set the starting address of the variables and constants at location 1000 The second org statement is to set the start address of the main program to be executed to location 1100 When you attempt to run your program you need to issue the command g 1100 in the miniIDE environment CR EQU 0D ASCII Code for Carriage Return LF EQU 0A ASCII Code for Line Feed getchar EQU EE84 Address of Debug12 Utility Function getchar printf EQU EE88 Address of Debugi2 Utility Function printf ORG 1000 Start Address of variables constants 13 msg getnewval terminate db ORG
14. nally connected together Before sending a number to a 7 Segment LED the number must be converted to its corresponding 7 segment code depending how the 7 segment display is connected to an output port The Dragon12 Plus2 board uses port B to drive 7 segment anodes and used PPO PP3 i e Port P to drive common cathodes In the next few paragraphs we will explain how to multiplex 7 segment by displaying the number 1234 on the display By convention the 7 Segments are called segment a b c d e f and g as shown in Figure 5 Figure 5 The Dragon12 7 Segment The segment a b c d e f g and Decimal Point are driven by PORT B PBO PB1 PB2 PB3 PB4 PB5 PB6 PB respectively The hex value of the segment code is shown in the following table The schematic for multiplexing 4 digits is shown in Figure 7 10 Number DP G F D cC B A Hex Value 1 oO o Oo Oo o 1 1 o 06 2 o 1 o 1 1 o 1 1 5B 3 oO 1 Oo o 1 1 1 1 S4F oO 1 1 o O 1 1 oO 66 Figure 6 Hex Value of the numbers 1 2 3 4 COMMON CATHODES Figure 7 Multiplexing the 7 Segment Displays on the Dragon12 Plus2 Board The digits 3 2 1 and 0 are driven by PPO PP1 PP2 and PP3 respectively PORT P The 7 Segment LED is turned on one at a time at 250 HZ refresh rate It s so fast that our eyes will perceive that all digits are turned on at the same time To display the number 1234 on the 7 Segment display the following st
15. nd J in functionality Por Register Descripion Addr PORT H PTH Data Register H Data Direction Register H Input Register H Reduced Drive Register H Pull Devide Enable H Polarity Select Register H Interrupt Enable Register Wakeup Interrupt Flag Register H Data Register J Data Direction Register J Input Register J Reduced Drive Register J Pull Device Enable J Polarity Select Register J Interrupt Enable Register J Interrupt Flag Register J Table 3 I O Ports with Interrupt Enable Capability Table 4 provides a brief description of other I O ports and registers that are used for Real Time Inter rupt Section 6 7 in Text Book Analog to Digital Conversion Section 12 3 in Text Book and Serial Communication Pa kese Dsoiption OO OOO o o Ar PORT ATD PORT SCI 0 RTICTL CRGFLG CRGINT ATDOCTLO ATDOCTLI1 ATDOCTL2 ATDOCTL3 ATDOCTL4 ATDOCTL5 ATDSTATO ATDSTAT1 PORTADO ATDODROH ATDODR7H SCIOBDH SCIOBDL SCIOCR1 SCIOCR2 SCIOSR1 SCIOSR2 SCIODRH SCIODRL Real Time Interrupt Control Register RTRO RTR6 The CRG Flag Register RTIF The CRG Interrupt Enable Register RTIE Control Register 0 Reserved Control Register 1 Reserved Control Register 2 ADPU Control Register 3 S8C S4C S2C S1C Control Register 4 PRS4 PRS0 Control Register 5 SCAN MULT CC CB CA Status Register 0 SCF Status Register 1 Reserved Data Input Bit7 Bit0 Result Register 0 High Byte
16. ut devices The input devices could be digital or analog Digital input devices include switches keyboards digital integrated sensors that send OV logic 0 or 5V logic 1 and so on There are many analog input devices for example all types of transducers A transducer is an analog device that converts some form of energy to an electrical signal this will be covered later on in the course 3 Preparation The preparation for this lab involves the familiarity with e I O parallel ports of the 68HC12 and programming them e The Light Emmitting Diodes LEDs on the Dragon12 Plus2 e The Seven Segment Display on the Dragon12 Plus2 3 1 MC68HC12 I O Ports The 68HC812A4 has 91 I O pins arranged in Twelve I O ports All of these pins serve multiple functions depending on the operation mode and data in the control registers Ports A through J and ports S and T are used as general purpose I O pins under the control of their associated data direction registers Port AD is fixed as either inputs for the A D converter or as logic inputs and does not have a data direction register Each pin of the bidirectional ports has an associated bit in a specific port data register and another in a data direction register The data direction register bits are used to specify the primary direction of data for each I O pin When an output pin is read the value at the input to the pin driver is returned When a pin is configured as an input that pin becomes a hig
17. zero tolerance for any form of academic misconduct Consultation with other students is encouraged especially on design issues However directly copying another student s work or copying portions of code for example assembly language code is an honour code violation and will result in a failing grade and may result in a failing grade in the course Students will automatically be referred to the Director of the School and Dean of the college for action Please refer to the regulations outlined in the student handbook regarding academic misconduct 6 Appendix A MCU Connections Eight pin header connectors H1 H8 surrounding the breadboard provide access to the MCU s I O and bus lines as seen in Figure 4 These connectors are located adjacent to the prototype area COMPATIBLE 3u G pave2 HEADERS g 2 5U IO PA7Z x Ecis c28 O PA6 c228 lojens RIB g gc24 Sens c23 EXTAL j R128 CO Ecze Spar on EE z H3 H4 bald CUE g Mdsisisisisisisisio sls o19 o Gs S o 9 S S S S S S S S1S A o rv vr H ONF OMN WERTET P See ae RE Bae Figure 4 Main Pin Headers on the Dragon12 Plus2 Board 1 Connector H1 located at upper left of breadboard 2 Connector H2 located at lower left of breadboard below H1 3 Connector H3 located at bottom left of breadboard 4 Connector H4 located at bottom right of breadboard 5 Connector H5 located at lower right of breadboard 6 Connector H6 located at upper right of breadboard
Download Pdf Manuals
Related Search