EsduinoXtreme User Guide
Contents
1. S12 can process an external interrupt this way However since the processor comes with several additional hardware interfaces built into it it makes sense that these interfaces are also set up to be able to trigger their own interrupts The result is that the system has now gone from one available interrupt to a large number of possible interrupts Therefore some way has to be set up so that if two interrupts happen at the same time one of the two can be specified as being at a higher priority and thus will be handled first Also not all the available hardware possibilities will be used in any one design So the unused interrupts must not be enabled There is one more complication added when using the serial monitor which appears at the top of flash memory Instead of relying on one interrupt routine to determine what device requested an interrupt each S12 interrupt source automatically causes the associated handling routine address to be fetched from a table called the Interrupt Vector Table For the S12 this table is by default at the very top of memory right in that same 2K memory space that the serial monitor is in Since that memory is protected it can t be changed by the serial monitor Okay a BDM pod can do it but that defeats the purpose of working with the serial monitor There are solutions to these issues and I ll cover them here As an example I ll use SCIO as the interface we want to set up to handle an interrupt from The steps w2. also be installed in a protective housing to keep it isolated from undesired external voltage sources Overview of features EsduinoXtreme comes equipped with a variety of interfaces and on board resources These include but are not limited to the following 8 MHz crystal providing a 4 MHz nominal bus speed when enabled This can be mutliplied by six using the on chip PLL resulting in a 24 MHz bus speed 1 MHz internal oscillator is the default clock source following powerup before the oscillator is enabled This minimizes current draw and EMI Memory resources 240K Flash 4K EEPROM 11K RAM e Operating voltage 5V or 3 3V jumper selectable Power sources via USB port by default can be powered externally via optional input jack through the on board 5V regulator using an external 6 12 VDC power source USB communication interface to host computer via FTDI chip utilizing microB USB connector User LED red LED on DIG13 Port J bit 0 available for application use e On chip development support adaptation of Freescale AN2548 Serial Monitor e BDM connector 6 pin standard header enables the use of a separate BDM pod for for programming all Flash and EEPROM memories and debugging programs in real time Input output headers emulate the Arduino Leonardo pinout with four of the signals user assignable via jumper blocks e Footrpint for optional user installed SPI memory device EEPROM or Flash in SO 8 package Option
3. as12 assembler will assemble the file sending the listing output to the console and writing the S19 object output to a file named m out You will want to then rename the m out file to something ending in s19 to load into the target system with uBug12 or a BDM pod Please note that SBASIC and as12 by themselves do not do any hardware setup It is up to you to write the code to set up the MCU hardware SynCode and Eclipse GCC The URL for these is http feaser com zip Imagecraft C Imagecraft C for CPU12 is a commercial product that supports HC S 12 microcontrollers It includes support for the NolICE12 debugger You can download and use it for free during a 45 day trial period There are special priced versions for students and non commercial users The URL is http www imagecraft com Cosmic C Cross Development Environment Cosmic C is a commercial product that includes the Cosmic S12 assembler and C compiler They also have a full featured BDM source code debugger available and full S12 simulator Their IDE is called IDEA It is available in versions for both Windows and Linux based computers The URL is http www cosmic software com s12x_des php Software Debugging Writing software is only the first part of the development process Next comes testing to verify the program functionality This requires not just running the application on the target system but having a means of tracing what is happening should something not function as ex
4. at the desired value Example taken from the Serial Monitor code S12SerMon2r7 SYNR equ CRGV4 S00 CRG synthesizer register REFDV equ CRGV4 01 CRG reference divider register POSTDIV equ CRGV4 S02 CRG post divider CRGFLG equ CRGV4 03 CRG flags register LOCK equ 00001000 lock status bit UPOSC equ 00000001 Oscillator Status Bit GIRS EME equ CRGV4 S05 CRG clock select register PLLSEL equ 10000000 PLL select bit PLLC I equ CRGV4 S06 CRG PLL control register PLLON equ 301000000 phase lock loop on bit CPMUOSC equ SO2FA 7S12CPMU Oscillator Register OscFreq equ 8000 7Osc speed i e external crystal frequency dna ES VNR equ 02 7 mult by syne 1 3 24MHz VCOFRQ equ 40 veo gain initREFDV equ 00 REFFROQ equ 80 7plll stability Ini tPOSTDIV egu 00 POSC Divider Register CPMUPOSTDIV movb initSYNR VCOFRQ SYNR set PLL multiplier movb initREFDV REFFRQ REFDV set PLL divider movb initPOSTDIV POSTDIV set post divider movb C0 CPMUOSC Enable external oscillator nop nop predir CRGFLG LOCK 0 while crg crgflg bit lock 1 beer CLKSEL PLLSEL pengage PLL to system Clock Usage The oscillator and bus clocks are used not just to sequence through instructions and time memory and peripheral accesses They are also used to dictate the timing of several other harware module capabilities such as SCI baud rate RTI COP timing and Flash EEPROM programming For example the baud ra
5. be aware of it is if you are preparing an S record file that will be used by Freescale to create a ROM version of the S12 for OEM use Notice that the address space for 240K Flash requires 20 bits to specify not 16 bits Obviously there is an issue here as the CPU can t directly access this much memory Furthermore Flash is not the only memory mapped device we want the CPU to access There are also RAM EEPROM and various I O Input Output devices such as that dancing penguin What Freescale did to solve this problem was to divide up the CPU logical space into sections each dedicated to its specific device We ll get back to this in a moment The next step was to devise a way to determine the value of the extra address lines each piece of hardware had To do that there had to be a way of tying all this hardware such as Flash and RAM together physically so that the CPU could address them The solution was to define something call the Global address space Global addresses start at 000000 and go to 7FFFFF and are the physical address space used to reach real hardware like Flash or RAM It takes 23 bits to define this address space providing room for 8 Megabytes of stuff With this much addressing range that 240K block of Flash can fit in just fine Furthermore room is reserved for larger Flash devices as well The internal devices of the S12 were then placed in the Global Address space at fixed locations Notice that Flash is at the top
6. before the S12 will start handling interrupts This can be done with the cli assembler directive which translates to andcc EF The bit is set whenever an interrupt routine is called by the Interrupt module It is possible for you to write your code to clear this flag on purpose while your interrupt routine is being processed Doing so will allow interrupts of a higher priority to interrupt the current routine while still preventing lower priority routines from stepping in It will also keep high priority interrupts processed in a timely fashion As you can see setting up interrupts is not for the faint of heart and requires careful planning for it to be done correctly Furthermore debugging interrupt code can be a nightmare The IDE simulator with its breakpoints can help here but it only goes so far For difficult problems this can require the use of a BDM pod with matching troubleshooting software and even a logic analyzer However don t let these difficulties keep you from using interrupts You can still do a lot even without a BDM pod It just requires using that space between your ears more Other Interrupt Caveats Some of the interrupts like SWI and XIRQ have slightly different rules for using them However the basics outlined here still apply Again you will need to read up on the documentation to use these effectively 12 Clock Since your application most likely will be designed to run upon power up of the module witho
7. filenames If that was the case that component would have to be enclosed in quotes Complete pathnames have to be specified too for it to work Therefore the command format used is cumbersome to type To help make this process easier an IDE like AsmIDE can be configured to do the command for us When using the HSW12 assembler you will need to keep the following points in mind 1 The assembler likes code fields separated by the Tab character rather than by a space This seems to be more an effect of using the ActiveState Perl interpreter than Dirk s assembler Under certain circumstances the assembler will flag a line as an error when the first character is a space rather than a tab or when a space separate fields like label and instruction haven t spent time noting the exact circumstances of the effect just use tabs regardless now and have not had a problem 2 Arithmetic expressions may have different rules of precedence than other assemblers You need to specify parentheses for everything to make sure expressions get evaluated correctly Evaluation seems to be right to left whereas other assemblers may be left to right The assembler is made to have the following precendence order amp gt gt lt lt 3 Comments after an instruction need to be prefixed by a semicolon or they are considered part of the instruction This also means that regardless of where a semicolon is in a line it starts the comment sectio
8. grow downward With 256 pages of 16k bytes each the maximum possible Flash that can be used by the S12 is 4 megabytes If that full amount were available then the page numbering would go from 00 to FF The default mapping of Flash to CPU Logical Address space on powerup is as follows Flash Bank FD CPU Address range is 4000 to 7FFF Fixed Flash Bank FE CPU Address range is 8000 to BFFF Window Actual Bank determined by PPAGE value Flash Bank FF CPU Address range is C000 to FFFF Fixed always The PPAGE register is in the CPU Address space at 0030 Changing the value written here determines the actual 16K Flash bank that is visible to the CPU in the 8000 to BFFF address range This is how the processor can execute code in any Flash bank Furthermore there is an instruction made just for this CALL With CALL the programmer can set it up so that the executing code calls a subroutine in another Flash Bank Various blocks can be re mapped via special registers following a reset event if desired The starting address for the RAM block is set via the INITRM register the location of the register block is re mapped via the INITRG register and the location of the EEPROM block can be re mapped via the INITEE register Interrupts Embedded systems are called such because they interface directly with the real world The interfaces used rarely are the video displays and keyboards a standard desktop computer has More likely they a
9. the Target tab of the programmer GUI click Detect Chip The Device Selection box should update automatically to display GA MC9S12GA240 If not you ll need to do some troubleshooting to figure out why not 8 At this point you re ready to load a program into flash so click on the Load Hex Files button to open a Windows file explorer from which you ll select the file you wish to load Just leave the default settings You can read up on the options later in the USBDM project documentation if you want to 9 If you haven t already done so downlaod and unZip one or more of the example projects for EsduinoXtreme from our Support Library at http support technologicalarts ca docs Esduino EsduinoXtreme Code CodeWarrior C 10 Using the file explorer opened previously via the HCS12 Programmer GUI navigate to a project folder and the subfolder called bin There you ll find the s19 file to load usually it s called Project abs s19 A suggested project to start with is Example_RTI Load the Project abs s19 file found inside that project s bin folder 11 Leave unchanged the defaults for Bus frequency and Security and ensure EraseMass is selected under Erase Options in Device Operations Click the Load and Go button and a second or two later you will see a Programming Completed message popping up You should also notice that the red LED on your EsduinoXtreme is blinking rapidly If you connect up another LED in series with a current limiting resistor to groun
10. A separate document on the Technological Arts website describes the installation functionality and operation of uBug12 BDM Pods USBDMLT This pod is based on the open source USBDM project on the Freescale Community Projects board and is supported as a Debug tool in CodeWarrior select TBDML It comes with a DLL for CodeWarrior that needs to be installed first however Check the Resources tab of the USBDMLT product web page for details and links to the files and documentation A small standalone Windows application called HCS12_Flash is also provided which enables loading s record files into virtually any HC12 S12 and S12X target nolCE12 This is a Windows based source level debugger for HC12 S12 and S12X targets with support for BDM pods including USBDMLT URL is http www noicedebugger com Software Considerations Software development can proceed more easily if you have a good understanding of the basics of how the 9S12G hardware works An understanding of memory addressing and interrupts is needed as a starting point This section provides that introductory background However for a complete definition of the 9S12G capabilities read the Freescale reference Memory Map PPAGE and banking are two terms you need to understand relating to addressing memory on the S12 Let s start with the CPU Central Processing Unit This is the processor that handles the actual machine code instructions It is designed with 16 bit regist
11. CIO interrupt handler s address should be in Flash at FFD6 and FFD7 Relocated to F7D6 7 with the serial monitor in use If two interrupts have the same priority then table position will determine the higher priority one Hardware Interrupt Initialization The next step is to set up the hardware interface so that it generates an interrupt when we want it to By default hardware generally will not send an interrupt to the CPU and so we need to configure it to do this Obviously this step is very dependent on the particular hardware we want to generate the interrupt Therefore you will need to read closely the documentation for the hardware subsystem you are using to make sure that it is done correctly Otherwise strange results will occur if any results occur at all For SCIO we need to set the baud rate first This is done at 00C8 and 00C9 You will need to read the documentation to determine the values to write here to get the baud speed you want based on the CPU bus clock The default value for Control Register 1 is good so we keep this by setting SCIOCR1 at 00CA to 00 Finally we enable the transmitter and receiver for SCIO and enable their respective interrupts at the same time by writing a value of AC to the SCIOCR2 control register at 00CB CPU Interrupt Enable The final step is to enable the S12 CPU to handle interrupts Following Reset the Codition Code Register has the Interrupt mask bit set This bit must be cleared
12. EsduinoXtreme User Guide Print Introduction The latest Arduino format board from Technological Arts is implemented with a full featured Freescale S12 microcontroller having Flash EEPROM and SRAM memories SCI SPI and CAN communications subsystems dual 8 bit DACs sophisticated 16 bit timer channels PWM and multi channel 12 bit analog to digital conversion capability EsduinoXtreme brings these features within easy reach of engineers educators and hobbyists Unlike other hobby boards which may use sub standard parts and undergo minimal testing EsduinoXtreme is manufactured to industrial specs and is suitable for OEM use This guide provides basic setup and operation instructions for EsduinoXtreme Included are both the hardware and software information needed to get the board working with a variety of programming languages and development tools The first step in preparing to use EsduinoXtreme is to read through this manual before attempting to apply power to the device WARNING The board contains electrostatic sensitive components and it is recommended that standard electrostatic precautions be taken when handling the module There does not have to be a visible spark for a dangerous voltage to affect the electronics Just walking accross a carpet on a dry day is enough to build up a potentially damaging amount of static charge Recommended precautions include using a wrist grounding strap and or a grounded workstation The module can
13. Warrior is considered the industry standard and is available in different suites from Freescale Each suite has different capabilities and prices The least expensive of these is the Special suite which is available for free Its main limitation is that it only allows C programs to compile to a maximum size of 32 KB The assembler is not bound by this limitation though On the other end of the suites is the Professional version which has no limitations CodeWarrior includes an IDE and a simulator You can find out more by visiting the Freescale site for CodeWarrior at http www freescale com webapp sps site prod_summary jsp code CW HCS12X amp fsrch 1 You will find a link on this page to download the Special suite of the software The link will download an executable to run that does the actual installation You will also need to download and install the relevant Service Pack to support he S12GA240 MCU used on EsduinoXtreme Please be aware that the file sizes are over 300 MB so it is best to use the fastest network connection possible Alternatively you may order a CD from Freescale to obtain the software Here are some other links for documentation to help get CodeWarrior up and running This is a comprehensive and therefore complex package Plan to spend some time learning how to use it CodeWarrior Documentation List Quick Start Instructions Compiler Documentation CodeWarrior Development Tools Learning Center While CodeWarrior can be u
14. al header footprint for adding wireless communications via the Digi XBee module using the Technological Arts ADXB adapter Setup and Verification of Hardware Power and serial connections default jumper positions There are two basic ways to use EsduinoXtreme in developmen which are described in detail belowt 1 On chip Serial Monitor with uBug12 You will need a microB USB cable in order to establish communications between EsduinoXtreme and your host computer The cable can also provide power for the board to a maximum of 500 mA supplied by your computer s USB port Note if you plug EsduinoXtreme into an upowered USB hub the available current will be less than 500 mA depending on what else is plugged into the hub 2 External Background Debug Module BDM pod Use a BDM pod such as our USBDMLT to program and power the board via your computer s USB port There is a jumper block on USBDMLT which you can use to select 3V or 5V operation If you want EsduinoXtreme to run your program without a computer attached you will need to supply power through one of several methods detailed in the next section Refer to the board s schematic diagram and feature sheet for details There are several jumpers placed on the board as well as pads to put jumpers When the board is first used there are only a couple of jumpers that need to be checked These are listed below along with their default settings A full jumper list is provided later JB1 se
15. an hold up to 128 interrupt routine addresses You will need to reference the S12 documentation to find out where each device s interrupt address is kept in the table The serial monitor implements a pseudo table for interrupts set aside at the F7 page in memory The reason for the pseudo table is that the serial monitor has to be able to manage its interrupts to function correctly The pseudo table will also allow detection of an interrupt triggered that no routine is written for it and let the serial monitor take over This helps in the troubleshooting process The pseudo table exists from F710 through F7FF Your reset vector will need to be programmed at F7FE or your application will not start on powerup even if the Load Run switch is in the Run position You might ask yourself What happens if two devices simultaneously ask for an interrupt to be handled There are two parts to the answer to this question and I ll handle the first part here The position of an interrupt address in the Vector table gives it a priority in relation to all the other interrupts So if two interrupts come in simultaneously the one that has the vector address higher in the table will be handled first That is why Reset which is considered an Interrupt has its vector at the top of the table at F FFE It trumps all other interrupts For our example the SCIO device is supposed to have it s interrupt handler address stored at the D6 location in the table The S
16. b to pick is 6808 Options as this is hardly used now For Full pathname of Assembler enter c Perl bin Perl exe For Full pathname of helpfile enter C nsw12 doc hsw1 2 html The last text box on the dialog is for assembler switches This should have hsw12asm pl L hsw12 perl s19 e You will need to have your source code located where the Perl assembler is at C nsw12 perl Now you can use the IDE to create assembler source files They can be assembled by going to Build gt Assemble on the IDE This will generate a file of S records that can be loaded into EsduinoXtreme MinilDE This is another IDE that comes with the asm12 assembler as its default It is located at URL http www mgtek com miniide SBASIC The SBASIC language is a no line numbers variation of BASIC with a compiler that runs on Windows computers It uses the as12 assembler to generate object code You will need to download as12 and install it to use SBASIC The URL for obtaining both SBASIC and the as12 code is http www seanet com karllunt sbasic htm Or if you prefer here at the direct links SBASIC ZIP archive as12 ZIP archive Once this is extracted to its own directory you will find within it the SBASIC compiler called sbasic exe SBASIC is a compiler that runs via a command line Use Start Accessories CommandPrompt in Windows to open a DOS Command Prompt window Typing the command without any parameters generates the follow
17. called EX_SCl rar and we ve placed the Project abs s19 file in the folder for your convenience that s the file that you should right click on and save to your PC Then use uBug12 or a USBDMLT pod to load that file into your board before using it see instructions for these two approaches below EsduinoXtreme comes from the factory pre programmed with a simple SCI demo program in Flash You can run this by placing the Load Run switch SW2 in the Run position when applying power or pressing reset The demo program requires use of an ASCII terminal program such as HyperTerminal on Windows systems to provide a means for you to interact with the program Besides setting the correct ComPort refer to http support technologicalarts ca docs USB 20Boards ConfiguringVirtualCOMports padf for help with this you ll need to configure the terminal program with the following properties Emulate ANSI terminal type 9600 baud 8 bits e One stop bit No parity e No flow control Do not append line feeds to incoming line ends No local echoing of typed characters When the SCI demo program starts it activates the red LED on the board and sends the following text out the serial port which consequently appears in your terminal window Technological Arts EsduinoXtreme SCI demo Input String Go ahead and type a character string of up to 20 characters and press lt enter gt Your string will then be echoed back in the terminal window an
18. ctors Notes on Serial Monitor EsduinoXtreme comes pre programmed with a serial monitor in the topmost 2K of Flash memory This monitor is based on Freescale s Application Note AN2548 adapted for 9S12GA240 by Technological Arts It is designed to function using the SCIO interface at 115200 baud with an 8 MHz crystal which it boosts to 24MHz using the PLL Besides activating the PLL it moves the RAM block and EEPROM block via the INITRM and INITEE registers to various addresses depending on the MCU variant To learn more about these details or to customize options such as which SCI to use which port pin for the Load Run selection bus frequency etc download and open the the serial monitor project in CodeWarrior where you can view and modify the def and asm files as required After building the modified project the new s record file will have to be burned into flash using a BDM pod e g USBDMLT from Technological Arts You ll find the the serial monitor project in the Technological Arts Support Library at http support technologicalarts ca docs Esduino EsduinoXtreme Code SerialMonitor
19. d with its anode connected to the DIG2 pin on the J1 header you ll see it blink at a 0 5Hz rate A Note that once you have loaded a program with USBDMLT the serial monitor that was pre programmed into flash at the factory is no longer present f for some reason you wish to use the serial monitor instead of USBDMLT you ll need to load it back in Follow the steps from 4 to 11 shown above and load the serial monitor s19 file found in the Support libary at http support technologicalarts ca docs Esduino EsduinoXtreme Code SerialMonitor Application Programming There are several language options available for writing application programs for EsduinoXtreme One can use Assembler C or BASIC or a combination of these This section lists descriptions and hardware specific setup instructions for the various options available The choice of what to use is left to the user Generally though it will be based on application requirements budget and what the programmer is familiar with or willing to learn Keep in mind that there is a difference between a programming language and an Integrated Development Environment IDE An IDE combines several functions of the development process into one program It can be designed to work with a specific language like C or Forth However the language does not define the IDE functionality An IDE can include an editor assembler compiler simulator debugger serial monitor interface or BDM pod interface or
20. d you ll be prompted to enter a decimal number Do so followed by enter and then enter a hex number when prompted Each time the value you entered will be echoed back in the terminal window the size of the numbers allowed max out at 16 bit Here s a typical session Technological Arts EsduinoXtreme SCI demo Input String good morning Output String good morning Input Decimal 32768 Output Decimal 32768 Input Hex f07e Output Hex FO7E Input String Each time through the session the program toggles the LED If you d like to examine the project you ll find it EX_SCI0 and other example CodeWarrior projects in our Support Library at http support technologicalarts ca docs Esduino EsduinoxXtreme Code CodeWarrior C The demo program serves as a reasonable confirmation that your board is working properly Now it s time to learn how to load other programs 1 Using uBug12 EsduinoXtreme comes pre programmed with the Technological Arts version of Freescale s Serial Monitor program in Flash After reset the setting of switch SW1 is examined by the code and the following actions result 1 If the switch is closed i e LOAD position control is passed to the Serial Monitor whcih initializes various parameters of the MCU and waits for commands to be received on the serial port via the USB connection Since the SerialMonitor uses a binary interface i e non ASCII it requires a companion application to be running on the host computer to p
21. e and find the subfolder inside PGO called Devices The path is something like C Program Files pgo USBDM 4 10 6 130 DeviceData 3 Plug your USBDMLT pod into an available USB port on your PC Launch the application called HCS12 Programmer that was included with the USBDM software 5 The program GUI has three tabs On the Interface tab you ll see the Select BDM field which should now be displaying USBDM JS16 0001 indicating that it has detected the pod If not click the Detect button to detect it If it can t detect your pod youo ll need ot visit the Help page of the USBDM project to resolve the issue 6 Next click the Target tab Plug the 6 pin ribbon cable into your EsduinoXtreme BDM port Note that this is the right angle male header directly adjacent to the J1 header Do not use the 6 pin vertical header adjacent to the slide switch that one is the SPI port Ensure that the cable is plugged in the correct way red stripe closest to the J1 header i e the ribbon cable is exiting from the bottom of the connector You may wish to snap the optional plastic strain relief onto the ribbon cable connector to make it easier to grasp for plugin and removal Ensure that the jumper is in place on the USBDMLT pod selecting either 3V or 5V operation That way the pod will power your EsduinoXtreme via the USB port of your PC Should you decide to use an external power source later e g battery you can remove the shorting plug entirely from the USBDMLT 7 On
22. e need to do are 0 Set the stack pointer 1 Initialize any pointers buffers etc needed by the interrupt routine 2 Initialize the S12 to handle interrupt input 3 Initialize the hardware to enable its interrupt output 4 Enable CPU interrupt flag in Condition Code register ere TSewa Stack Pointer Before any interrupts can be handled the CPU stack pointer has to be initialized This is done with a LDS instruction and need only be done once in your setup code Be sure you set it up to point to a valid location in RAM and that you reserve plenty of space for it to grow into Stacks grow down towards lower memory addresses Oh yeah not using a valid RAM location will crash your system Usually the stack pointer is used to store the return address when calling a subroutine or to store temporary variables However in the case of an interrupt all the CPU register values are stored on the stack when the interrupt begins processing That way when the interrupt processing routine finishes the entire CPU state is restored Whatever routine got interrupted should never know it Therefore when writing an interrupt processing routine it has to end with an RTI or Return from Interrupt instruction RTI expects to find all the CPU registers stored on the stack in a certain order so it can restore the CPU state as required when it is executed If your interrupt routine does not leave the stack exactly as it found it you will crash the sy
23. ers such as X Y and PC Program Counter As such it can address some 65 536 bytes directly 64K and not one byte more nor less It does not care what is on the other end of an address be it a register RAM Flash or a penguin dancing on a keypad An address is just a place to read or write an 8 bit byte Every piece of hardware that the CPU communicates with has to map somewhere into this address space We will refer to the CPU address space as the Logical Address It makes logical sense to the CPU to find stuff here One consideration to keep in mind regarding memory accesses is that the CPU is designed as a 16 bit processor As such its accesses are optimized when it is doing fetches and writes to even addresses An even address has a zero in the Least Significant Bit position If the CPU has to do a word access with an odd address then it actually has to make two accesses and then manipulate the results to produce the expected results This increases latency So be sure to remember this when setting up tables that will be read frequently Instruction fetches have this issue mostly alleviated by the use of an instruction queue There are various memory resources that have been included on the S12GA240 chip The Flash consists of 240K of memory Physically a 240K Flash memory would have its memory cells addressed from 00000 to 3DFFF This physical address for Flash is never used by the S12 directly though The only time you really need to
24. he SETDP directive You can force direct addressing by prefixing the target address with the left angle bracket character Once you have an S record generated you can program it into your module using the appropriate method for the hardware variant you are using e g uBug12 for the Serial Monitor or any compatible BDM pod AsmIDE AsmlDE is not an assembler but an IDE that comes with the default as12 assembler and is capable of being adapted to using Dirk s HSW12 assembler if desired The install package for this IDE is available from several sites The URLs are http hcesl2text com files asmide340 zip http mamoru tbreesama googlepages com asmide340 zip http mamoru tbreesama googlepages com asmide src zip This provides the source To set this up to use the HSW12 assembler you will first need to install the assembler and Perl interpreter as per the instructions previously provided in the HSW12 section Next download the AsmIDE zip file and extract the files into a directory created to contain them You will find in your directory an executable called AsmIDE exe Start the AsmIDE exe program so that it can be configured Once the application window appears Go on the Menu bar to View gt Options This will bring up a dialog box that sets the IDE options e Select the Assembler tab at the top e You will need to change one of the default CPU settings Under Currently Selected Chip family select 6808 The recommended ta
25. he total current draw will be limited if the system is powered via the USB port instead of an external power supply Another limiting factor is heat At room temperature the regulator by itself will only be able to dissipate about two watts of heat The amount of dissipation needed will depend both on the input voltage applied and the current drawn to feed the electronics So a power supply at 6 volts will not cause the regulator to heat up as much as a 12 volt supply will If you need to dissipate more heat than two watts though you must add a heat sink to the regulator Appendix Electrical specifications Input Voltage Optional connectors J6 or J7 will accept a positive voltage from 7 12 Volts DC to provide VIN when a USB connection or USBDMLT pod connection to a host computer is not used Operating Current 50 mA nominal The on board regulators can provide up to 700 mA so external circuitry connected to the headers can safely be powered from the regulator The total current that may be drawn before the voltage regulator s thermal shutdown circuit engages depends on the input voltage and ambient temperature Operating Temperature Range 20 C to 70 C Note the temperature range is limited mainly by the rating of the crystal A broader range of 40 C to 85 C can be accommodated by using an extended temperature range crystal or the internal 1 MHz oscillator Board Dimensions nominal 2 70 68 7mm x 2 1 53 4mm x 0 475 12mm excluding conne
26. ing message providing a summary of it s usage SBasic compiler version 2 7 for the 68HC11 68HC12 usage sbasic infile options where infile is the name of an SBasic source file Input files have a bas extension by default Output will be written to stdout Options are cxxxx VXXXX SXXXX b mxxxx i where xxxx is an address given as four hex digits CXXXX sets first address of executable code VXXXX sets start of variables SXXXX sets top of return stack b generates branch opcodes not jump opcodes MXXXX sets target MCU 6811 or 6812 Ji does not generate interrupt vector table There are several sample programs included in the archive with SBASIC along with a manual that explains its use in greater detail You can pipe the output to a file that can be used by the assembler sbasic infile gt outfile You must specify options to have the program generate code that will work on the S12 as the default values will not work Read the manual for more information on the options for variable location stack etc that must be configured Once SBASIC generates an assembly file you will need to use as12 to parse that file It in turn will generate an S record file that you can program into your target board To start the as12 assembler enter the following command at the prompt asl2 file ext where file ext is the path name and extension of the file you want to assemble in this case the output saved from the sbasic command The
27. lects the voltage source for running the board The factory default is USB meaning that 5V from your computer s USB port will supply power to everything on the board The VIN position would only be used if you were to supply power externally via optional 2 pin Molex header J6 or optional barrel jack J6 or via power pins on header J4 JB3 through JB6 provide user selectable signal assignments to some of the J1 and J3 header pins and can be moved to the desired position for specific applications Their configuration does not affect the basic operation of the board JB7 selects the operating voltage of the MCU A shorting plug must be in place in one of the two positions in order for the MCU to run If it is missing the MCU will not run JB8 selects the source of the Voltage Reference input pin VRH on the MCU which is related to the analog to digital converter subsystem The default position is VDD meaning that analog voltage conversions will be referenced to the MCU operating voltage set by JB7 described above Leaving this jumper off will result in undefined operation of the analog to digital converter subsystem JB9 is a three way selector block for communications between the host computer s USB port the SCIO pins of the MCU and the optional XBee RF module interface The default positions are US meaning that the USB to UART chip s RX and TX lines are connected to the MCU s RX0 and TXO pins i e SCIO Refer to the schematic diagram and feat
28. n Therefore the semicolon can t be part of of an instruction parameter like FCS CODE where the programmer assumes the semicolon is supposed to be part of a string 4 If you need to use Indexed indirect Program Counter Relative addressing you will have to use the format TARGET for the instruction target address Dirk does do offsets relative to the PC register but uses this format to implement the PCR option seen in some other processor assemblers So to do an indirect jump to an address held in memory location TARGET the code will be JMP TARGET _ Instruction is generated with offset relative to the PC register 5 S2 records generated need to be checked carefully to make sure they are created to go into the correct place in memory Using the ORG instruction can be tricky and will produce bad results if not done correctly Please read Dirk s comments on this thoroughly 6 The BRA instruction will change automatically to an LBRA instruction if the target address gets too far away This is generally a good thing but it does add two extra bytes to the code So be aware of it if you end up needing to count bytes used by a routine You can force the assembler not to switch to LBRA by prefixing the target address with the left angle bracket character lt 7 By default the assembler assumes direct page addressing for addresses starting in 00xx If you change the contents of the Direct Page register you can let the assembler know about it with t
29. of this address space and here is where things like PPAGE fit in To be able to specify the extra address bits which the CPU can t access registers were defined to accommodate the values for the additional address lines PPAGE is specifically for Flash Code can only be run in the Logical Address space of the CPU To allow Flash for example to be able to run code routines stored in it it has to be mapped into the Logical Address space of the CPU directly This is done by dividing up the Flash into pages of 16K each Two of these pages are then fixed into the CPU Logical Address space They are always there Okay there are lots of caveats and exceptions could be going into here but I m not going that far for now This way code can be placed in these fixed pages so the CPU has something to tell it what to do when power is first applied This is why the interrupt vector table is in Flash by default Space is also allocated in the Logical Address space for a third 16K Flash page The hardware Flash page appearing here though is determined by the value of the PPAGE register For a 240K Flash the 16K pages are numbered starting at F1 and going to FF One would think that numbering them should start at 00 and go to 0F but such is not the case This partially has to do with where the Flash is in the Global Address space namely at the top As the possibility exists for larger versions of Flash to become available over time the space taken by Flash will
30. pected There are two methods of accessing the S12 processor to do debugging The first is by using the flash resident Serial Monitor The second is the use of an external BDM pod Each method has value and which is used will depend on the needs of the development process and the available budget Serial Monitor The basis for the serial monitor pre programmed into EsduinoXtreme is described in detail in Freescale document AN2548 It provides a means to assist in debugging S12 code among other capabilities However the serial monitor by itself can not do anything It is designed to work with an external program that communicates with it uBug12 Because of this the serial monitor has a requirement that an SCI port must be dedicated to its use Therefore if you use the serial monitor as part of your troubleshooting process that SCI port cannot be used by your application program The serial monitor uses the SCIO port on the board so you are free to use SCI1 for your application if needed The AN2548 document is available for reference at http www freescale com files microcontrollers doc app_note AN2548 pdf fsrch 1 uBug12 Technological Arts provides a multi platform Java program called uBug12 as a means of interfacing with the serial monitor in Flash The program enables the user to manage the use of Flash memory and it provides standard troubleshooting capabilities such as examination and modification of both CPU registers and memory locations
31. re things like temperature sensors motor drivers and so forth A common consequence of this is that the programs written for an embedded system have to be able to respond quickly to external events occurring asynchronously to the program execution state The best way to process these events and have them work with your program is to set up interrupts An interrupt is a way to make an asynchronous event synchronous with your program Basically what happens is that some event external to the CPU signals the CPU to stop doing whatever it is doing and to spend some short amount of time dealing with the external signal After the CPU finishes what it needs to do it can go back to whatever it was doing before the interrupt happened The typical way of doing interrupts would be to have a software routine usually in assembly language set up to be called at a specific address The address could be fixed or specified in a table An external pin on the processor would be pulled low by the device requiring handling The only other fact to remember is that there is a flag set aside in the condition code register to mask the interrupt or allow it to be processed Usually the interrupt would only be masked when it was absolutely necessary in the main program An example is when the program reads a variable that is itself changed by the interrupt routine The interrupt must be masked while the read takes place and then enabled again after the read is completed The
32. rovide an interface to the user Technological Arts has created a freely downloadable Java program called uBug12 for this purpose which can run on Windows Mac and Linux hosts 2 If the switch is open i e RUN position control is passed to the user program in Flash via the user program Reset vector If the user reset vector has not been programmed control will revert to the monitor as described above To use uBug12 you will first need to download and install it Refer to the uBug12 manual for instructions and a link to the downloadable file When you are ready to proceed place switch SW1 in the Load position and connect a microB USB cable between your computer and EsduinoXtreme You can find instructions on how to download and use uBug12 at this URL http www technologicalarts ca shop documentation 63 debugging tools 1 7 1 ubug12je user manual html 2 Using a USBDMLT pod 1 Ensure that you have downloaded and installed the latest USBDM project from SourceForge 2 As of version 4 10 6 130 the S12GA240 was not yet included in the devices list for this project We have created an updated xml file which includes the S12GA240 Download this file called hcs12_devices xml from our Support library http support technologicalarts ca docs Esduino EsduinoXtreme Code USBDMLTfile and overwrite the corresponding xml file on your PC You ll find where to put it by navigating to the Windows program folder on your PC where the program files resid
33. sed to generate s19 files it does not support direct interface through the on chip serial monitor uBug12 can perform that function by enabling you load the generated files into your board However if you d like to use CodeWarrior for seamless loading and interactive debugging you will need a BDM pod that is compatible with CodeWarrior CodeWarrior is not guaranteed to work with all BDM pods so be sure to see the list of compatible BDM pods in the Freescale documentation The Technological Arts USBDMLT which is a low cost implementation of the open source USBDM project works very well and has the advantage of providing power to your board via the host USB port Dirk Heisswolf s HSW12 This S12X XGATE assembler is part of Dirk Heisswolf s HSW12 IDE This is a freeware IDE and assembler available on the web The site is listed in the instructions that follow The main difference between this development platform and others is that it is designed to be run on Linux systems The IDE is also designed to work with a BDM pod when loading and debugging programs However the assembler itself can easily be made to run on Windows computers with the additional installation of a Perl interpreter which is also freely available Here are the instructions to install Dirk Heisswolf s assembler on a Windows computer Get the free ActiveState Perl executive installed To do this first go to the URL http www activestate com Under Community Tools click on Ac
34. some subset of these capabilities It will depend upon the IDE So review what each can do before choosing one to work with An IDE can be useful because it can combine several development steps into one or allow blending of the functions e g source level debugging or using both assembly and the featured language To assist you in getting a better idea of what is available here is a table of the major development platforms that are available and that can be used to develop software for EsduinoXtreme Language Assembler IDE aa BDM Com Other free CodeWarrior Special C x 32K limit for C unlimited assembler CodeWarrior Pro C x commercial product HSW12 Assembler x Linux AsmIDE Assembler Windows MinilIDE Assembler Windows ISBASIC BASIC DOS based IGCC Syncode Windows IGCC Eclipse C Windows Imagecraft C Cc as12 x x some commercial product Cosmic C C S12X x x commercial product All of these will work with an assembler and allow assembly code to be embedded within the language The main difference will be in whch assembler is used There are several S12 assemblers available that can be used to write software Code Warrior from Freescale Cosmic Software s cas12x part of their C programming environment and Dirk Heisswolf s HSW12 Each of these come with their own IDE programs as well What follows are brief descriptions and instructions where needed for each of these development tools CodeWarrior Code
35. stem Been there done that Interrupt Routine Initialization Your setup code needs to make sure that before any interrupt handling is enabled that any variables that the interrupt routine accesses are initialized correctly This includes counters buffer pointers buffer contents etc This may seem obvious but a lot of software problems come from not noticing or taking care of the obvious stuff 12 Interrupt Initialization Now we start getting to the fun stuff The first item to set up is where the table of interrupt vectors is in memory and to do that we need to understand what exactly is an interrupt vector table In the typical processor discussed previously there is only one interrupt address to deal with for the one interrupt pin on the processor chip The S12 could have stayed with this and left it to the interrupt routine to determine which hardware device triggered it However this approach ends up being wasteful of CPU cycles and that can really hurt a system designed for high performance embedded use The alternative is to have each integrated hardware device provide the CPU directly with the address of the routine to handle its interrupt needs This is what the Interrupt Vector Table is for When an S12 device triggers an interrupt that request is handled by the Interrupt module The Vector table the module manages occupies a 256 byte block of memory Since each routine address is specified by two bytes of memory the table c
36. te for any of the SCI interfaces is set by this equation baudRegister BusFreq 16 10 baudrate Here the BusFreq is the system bus frequency as determined above in KHz This will usually be 24000 KHz The baudrate value is the desired baud divided by 100 So 9600 becomes 96 etc The resulting baudRegister value is then programmed into the SCIBDH and SCIBDL registers as the high and low bytes of the value respectively Obviously if the system bus clock is changed to a different value then this will affect the baud rate programmed into the SCI module Example coming soon Hardware Details Input Output Connectors The four main I O connectors follow the Arduino Leonardo standard for pincount and location and attempt to match up signals from the MCU to similar signal types used on Arduino Leonardo Additionally a 6 pin header bringing out the SPI pins is implemented in the same physical location of the board to provide compatibility with shields that depend on this feature Unused pins on this header have been assigned to VDD so as to make the header more versatile Since the S12GA240 MCU has a higher pincount than the Atmel MCU used on Arduino Leonardo there are some extra choices that have been implemented with jumper blocks so that the user can decide assignments on an application by application basis 12C implementation since the S12GA240 does not have a dedicated I2C subsystem 12C functions must be bit banged in software
37. tivePerl On the next page that appears click on the ActivePerl Download Now button Choose to Save the file After it is saved then double click on the file to run it You have to agree to the license to proceed Standard settings work fine Just click on Next each time it shows NOOR WOOD 8 The Perl interpreter is now installed on your computer 9 Get Dirk s freeware S12X assembler installed To do this go to his web site at http home arcor de hotwolf 10 Click on the Download link 11 Click on Save when prompted and choose where to save the file 12 Once this file is saved you will have to uncompress the archive However if you used IE to get the file the file you get is also an archive If you use Firefox you don t get this extra complication 13 To uncompress this file first rename it so it has a zip extension 14 Now decompress the zip archive 15 Take the folder that is created called hsw12 and move it to the root directory of the C drive To run the assembler a DOS command window will have to be used This can be done by going on your Windows system to the Start button and clicking on Run under that The command to run is cmd This will bring up a DOS window to type commands in Here is an example of the command to run to use the assembler c Perl bin Perl exe hswl2 perl hswl2asm pl MyProgram Fconfig asm s19 L hswl2 perl Note that there are no spaces used in the pathnames or
38. ure sheet for details on other possible configurations USB Interface EsduinoXtreme can communicate with a PC using one of the MCU s on chip Serial Communication Interfaces SCls through a USB to UART interface chip made by FTDI If you plan to use this interface you ll need a microB to USB A cable The first time you plug the board into your computer it will need to install USB drivers for the USB interface chip If you are using Win7 or later it should find the necessary drivers and install them automatically However if you re using WinXP you ll need to download the drivers from www ftdichip com vcp and install them yourself After successful driver installation you can determine which virtual com port Windows has assigned to your board by using Windows Device Manager via MyComputer Properties Hardware and looking at the comport list It will show you the USB com port assignment number e g COM6 You ll need to know that in order to access it through a terminal program or via uBug12 with the built in monitor program Using the Factory Installed Demo Program Note Boards shipped before 1 27 2015 did not have this program loaded Instead they have a program which simply flashes the LED continuously there s no serial communication To continue with this section if you have one of those board fetch the Demo program from our Support Library here http support technologicalarts ca docs Esduino EsduinoXtreme Code CodeWarrior C The program is
39. ut the support of the serial monitor it will need to configure the clock registers on the 9512G hardware The reason for this is that if the Load Run switch is in the Run position the serial monitor detects this setting upon powerup or reset and jumps immediately to your application as pointed to by the address you put in Flash at F7FE F If you do not program this location the serial monitor will take control regardless of the Load Run switch position When the serial monitor starts your application following reset it does not configure any of the hardware registers first It goes directly to your code After reset MCU clock is in PEI mode refer to 10 1 2 in S12G Manual so Bus Clock MCLK is 6 25 MHz This means the oscillator based upon the external crystal is not enabled and the bus clock is generated from the internal 1MHz oscillator boosted by the PLL to 25MHz and divided by four resulting in an MCLK frequency of 6 25 MHz How is the clock set then to the speed you want To do that the hardware uses the following equations PLLClock 2 Oscillator SYNR 1 REFDV 1 BusClock PLLCock 2 The BusClock frequency is the one we want The Oscillator term is the frequency of the crystal oscillator attached to the chip or the frequency being fed into the MCU on the EXTAL pin EsduinoXtreme has an 8 MHz crystal so this will be the oscillator value The registers SYNR and REFDV will need to be initialized to get the system clock
40. via the assigned pins connected to J3 pins 9 and 10 or via any other convenient pins The EsduinoXtreme feature sheet details the signals for each header pin using the pin names shown in Freescale documentation Note that several pins can have more than one function depending on how the hardware registers are configured Furthermore some hardware subsystems can be re mapped to different ports Refer to the Freescale manual for the MC9S12G for details Voltage Regulator Configuration EsduinoXtreme has two on board regulators U2 supplies 5V and U3 supplies 3 3V U2 takes the filtered DC voltage 6 12 VDC applied to one of the optional VIN connectors J6 and J7 or applied to the VIN pin on header J4 and provides a smooth regulated 5 Volts DC to the components When jumper block JB1 is set to VIN this 5V rail is active Otherwise 5V comes from the USB connector and U2 is not used In either case the 5V rail is fed to 3 Volt regulator U3 which produces a 3 3V output for use when the MCU operating voltage is set via JB7 to 3V and which also appears at the 3V3 pin on header J4 for use by application shields if required The 3V supply is also used to power the optional XBee module if it is attached via user installed header J10 since it is a 3V device If you plan to use the on board regulators to power your own circuits in addtion to the module please be aware that the regulators are rated to supply a maximum of 700 mA total current each but t
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