EE 308 Lab 1 Spring 2002 EE 308 – LAB 1 ASSEMBLER
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1. Figure 2 An assembly language program used to get started with the CA6812 ZAP and D Bug 12 Question to answer before lab What are the contents of the A register after each instruction of the program shown in Figure 2 executes We will use D Bug 12 to explore the memory of the HC12 on your EVBU The memory map for your 68HC12 is shown on page 31 of the MC68HC912B32 Technical Summary Most of this memory is used by the D Bug 12 monitor Page 3 55 of the M68EVB912B32 Evaluation Board User s Manual shows the memory available for your use Question to answer before lab How many bytes of RAM are available for your use on the EVBU Type the program shown in Figure 2 before coming to lab and save it under the name lab01 s You can also use a web browswer to download the program Also create the file 1ab01 1kf which contains the following lines EE 308 Lab 1 Spring 2002 Link file for program lab0l s seg text b 0x0800 n text program start address seg data b 0x0900 n data data start address lab0l o application program You can assemble the at home using the demo ca6812 assembler with the commands gt ca6812 a l1 xx pl lab0Ol s gt clnk o lab01 h12 m lab0Ol map lab01 1kf gt chex o lab01 s19 lab01 h12 The ca6812 command will create a file called 1ab01 o which contains the machine codes in a special form which other programs can read It also creates the file Lab01 1s which2. e What is the D Bug 12 command to change the Program Counter e Use the BF command to load 0x55 into memory locations 0x0980 to 0Ox09ff Use the MD com mand to verify that it worked Answer the following questions about the EVBU e What software resides in memory locations 0x8000 to OxFFFF e What value is the stack pointer loaded with when D Bug 12 initially starts up after reset
3. 1 after the program has finished Change the input data from 07 to Sbe and rerun the program Check the results Some questions on the simulator e How do the contents of the A register compare to what you predicted in the Pre Lab after the execution of each in instruction e Change the contents of the B register to 0xAC Change the contents of the A register to OxDC Set the stack pointer to 0x09D0 Hint How did you change the program counter e How can you put 0x3421 in the X register How can you verify the change took place Do it to see if your ideas are correct e What do the four columns in the Disassembly window represent e Reset the program counter to 0x0800 and rerun the program Display memory to look at input and result Is result equal to input 2 If not why EE 308 Lab 1 Spring 2002 When you have finished exploring the simulator type QUIT or EXIT Connect your EVBU to your computer and power supply as you did in last week s lab and power up your HC12 Open a terminal to the HC12 by double clicking on the jtt Win 3 11 Terminalj ttz on your desktop To download your program to your EVBU type LOAD atthe D Bug 12 prompt Then select the Transfers menu Send Text File submenu and select the file 1ab01 s19tosend Wait for the HC12 to respond with gt Using your EVBU do the same things that you did on the simulator and answer all of the questions from the simulator section that are applicable to the EVBU In addition
4. shows what op codes were generated by the assembler The clnk command will translate the 1ab01 o file into a form which the ZAP simulator can understand It also creates a file 1Lab01 map which shows where in memory the program will be loaded The chex command will create a s19 file which is the file you will use with the HC12 evaluation board Bring a disk with the program on it to the lab As you gain experience you will operate independently in the lab However for the first few labs you should be pestering the lab assistants to distraction to make sure you get everything that you can from the time in the lab We are there to help Your part is to take the pre lab seriously and show up for the lab session prepared The Lab Create a directory for this course say D EE308 Inside this directory create a subdirectory for this lab say D EE308 LABO1 Change to this subdirectory type in the lab01 s program and assemble it with the commands shown above Some questions on the output of the assembler e Look at the Lab01 1s file Where will the machine code for the instruction staa result be stored in the HC12 e What machine code is generated for the staa result mnemonic Is this what you expected Look up the STAA instruction in your CPU12 Reference Manual to determine what code this in struction should generate e At what address will result be located in the HC12 memory Start the ZAP simulator Once you are in th
5. EE 308 Lab 1 Spring 2002 EE 308 LAB 1 ASSEMBLER SIMULATOR AND MONITOR Introduction and Objectives This laboratory introduces you to the following 68HC12 assembly language programming tools e The 68HC12 assembler CA6812 This runs on the PC e The 68HC12 simulator ZAP This also runs on the PC e The D Bug 12 monitor that runs on the 68HC12 An assembler takes assembly language code in a form that a human can reasonably read with a little practice translates it to machine codes which a microprocessor can understand and stores them ina s19 file which the 68HC12 microcontroller can understand In this lab we will use the Cosmic Software CA6812 assembler which is on the PCs in the Digital Microcontrollers lab This is copyrighted software which is licensed for use on our lab computers only There is a demo version of this assembler as well as the Cosmic C compiler available It should be adequate for most of the labs in this course Information about how to obtain this demo assembler and compiler will be posted on the EE 308 web page In your HC12 kit you received a copy of the P amp E Microsystems ASM12 assembler You may put this assembler on your own PC and may put it in your directory on the EE computer system Using this assembler you can do much of the assembly language programming at home IASM12 is similar to the Cosmic assembler we will use in lab The Cosmic CA6812 assembler produces an output file with a h12 extension which
6. What is the difference between the MD and MDW commands e How would you change the value of the B accumulator to 0x55 Spring 2002 The assembly language commands of interest are LDAA STAA TAB ABA and ASRA Read the descrip tions of these commands in the 68HC12 CPU12 Reference Manual At this point you will not understand everything the reference manual says about these instructions but you should understand enough to get you through this lab Figure 2 is a simple program for the HC12 We will use it to illustrate how to use the assembler the simulator and D Bug 12 EE 308 Lab 1 Spring 2002 7 6 8HC12 demo program Bill Rison 7 1 22 99 This is a program to divide and multiply a number by two and store the results in memory title LAB 2 Demo Program evbram equ 0800 70x0800 is start of user ram on 68HC12 prog equ evbram start program at beginning of RAM data equ evbram 0100 CODE section text The stuff which follows is program code org prog set program counter to 0x0800 ldaa input Get input data into ACC A asra Divide by 2 staa result Save the result ldaa input Get input data into ACCA tab Put the same number into ACCB aba Add the number to itself multiply by two staa resultt l Save the result Swi jEnd program return to monitor in HC12 DATA section data The stuff which follows is data org data input dce b S07 first input data result ds b 2 reserve two bytes for results
7. e simulator load the h12 file using the File menu Go to the Show menu and click on Memory Give a starting address of 0x0800 and a Data format For Size select Byte Adjust your desktop so you can see the Registers Disassembly Command and Memory windows In the Disassembly window you should see the 1ab01 program 4 EE 308 Lab 1 Spring 2002 Question e What value do the HC12 registers have in the Register Window Trace or single step through your program using the i st ep command in the command window or clicking on the Foot step icon and observe what is going on in the Disassembly and Register windows When you are done single stepping do the following e Set a breakpoint at the swi instruction Do this by double clicking on the address of the swi instruc tion in the Disassembly window The address should become hightlighted in red You need to set a breakpoint so the simulator will stop at this address it does not have D Bug 12 loaded to recognize the swi instruction e Reset the program counter to 0x0800 You can reset the program counter by entering the command Zap gt eval Spc 0x0800 in the Command window or by double clicking on the pc in the Register window and typing in the desired value e Run the entire program You can run the program by entering the command Zap gt go in the Command window or by clicking on Green Light icon on the icon bar Check that you have the expected values in result and result
8. the ZAP simulator uses It also produces an output file with a s19 extension which can be loaded into and run on the 68HC12 The D Bug 12 monitor running from HC12 EPROM loads 19 records into the HC12 and provides some tools for debugging loaded programs The ZAP simulator simulates the operation of the 68HC12 on a computer This has two advantages you can try a program without having a 68HC12 and you can easily see information such as register contents number of cycles to complete etc which are difficult or impossible to observe on an actual microcontroller Again the full ZAP simulator is a licensed program which cannot be distributed but we have a demo version of the simulator which will be adequate for most of the labs in this course The relationship between these various programs is illustrated in Figure 1 Pre Lab You should read this entire lab before coming to lab and answer all of the questions in the pre lab section before coming to lab The D Bug 12 commands of interest for this lab are ASM BF BR NOBR G HELP LOAD MD MDW MM MMW RM RD and T Read the descriptions of these commands in Chapter 3 of the M68EVB912B32 Evaluation Board User s Manual EE 308 Lab 1 lab01 h12 __ lab01 s CA6812 ZAP lab01 s19 y Figure 1 The relationship between CA6812 ZAP and D Bug 12 Questions to answer before lab D Bug 12 e
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