The purpose of this lab is to write a few assembly language programs and test them on the simulator and on your EVBU.

As in last week's lab you will write some programs in assembly language and run the programs on the HC12 simulator and the EVBU. To make sure your programs work you will use D-Bug 12 op codes as your input data. There is one problem when running programs on the simulator - D-Bug 12 code which is present in the EVBU is not on the simulator. We can fix this problem by loading D-Bug 12 into the simulator. The following tells you how to do that.

• Open a 4DOS (or DOS) window and give the following command at the command prompt:

     net use e: \\timor\pclib
  

  This will mount a disk which contains an H12 file of D-Bug 12.
• Start the ZAP simulator. Load the file e:\ee308\dbug12.h12

Write and run the following programs:

1.

Write a program which writes an 0xff to address 0x0002, and then increments address 0x0000 indefinitely. (Note: this is a four-line program.)

Test your program both on the simulator and the EVBU. Trace through the program on the simulator and observe what happens to the data at address 0x0000. Check that the port PA lines are being toggled on your EVBU. (Use a logic probe to verify that the Port B lines are toggling.)

2.

Write a program to swap the last element of an array with the first element, the next-to-last element with the second element, etc. The array should have 0x20 eight-bit numbers and should start at 0x0900. (This is a problem from the homework due Feb. 4.)

Check that your program works both on the simulator and the EVBU. Use the following data for your test:

	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
090	00	01	02	03	04	05	06	07	08	09	0A	0B	0C	0D	0E	0F
091	10	11	12	13	14	15	16	17	18	19	1A	1B	1C	1D	1E	1F

3.

Write a program to compute the sum of the positive numbers of an array with 0x30 signed eight-bit numbers. Store the sum at 0x0900-0x0901. The array starts at 0xe000. (This is a problem from the homework due Feb. 11.)

Test your program on the simulator and the EVBU. What is the value of the sum stores at 0x0900?

4.

Write a program that puts the smallest one-byte signed number from memory locations 0xFCE0 through 0xFCFF in accumulator A and memory location 0x0900. (Note: The smallest possible one-byte signed number is 0x80 = -128₁₀.) Test your program on the simulator and EVBU.

5.

Write a program that puts the lowest unsigned number from memory locations 0xFCE0 through 0xFCFF in accumulator A and memory location 0x0900. (Note: The lowest possible one-byte unsigned number is 0x00 = 0₁₀). Test your program on the EVBU. Note that this program will be the same as for Part 4 with one instruction changed.

You can load programs into the on-chip EEPROM. When loaded in EEPROM your program will remain on your HC12 even after turning off power. Before loading your program into EEPROM, you must re-assemble it after modifying your program to start your code at address 0x0D00.

The details of how to download your program into EEPROM are given in the Universal Evaluation Board User's Manual in Appendix E, and are summarized here, with a description of how to make this work with our computers.

• Modify your program to put the code at address 0x0D00. Add this instruction as the first instruction in your program:

             clr   $16    ; Turn off the COP reset timer
  

  Leave the data at address 0x0900. Modify your lkf link file to put the .text section at address 0x0D00.
• Make sure you are talking to your EVBU with a Windows 3.11 Terminal. (The Windows 95/98/NT Hyperterminal will not work for this).
• Move jumpers W3 and W4 to their other position (position 1), then reset your board.
• On the Windows 3.11 Terminal menu bar, select Settings, Text Transfer, Line at a Time, Wait for Prompt String, and type in a `*' as your prompt string (without the quotes).
• From the HC12 command prompt, type L (for LoadEE). Go to the Transfers menu, choose Send Text File, and send your S19 file which was assembled to place the program into EEPROM.
• After the HC12 responds Programmed, hit the STOP icon at the bottom of the Terminal window, then change your Terminal Text Transfer settings back to Standard Flow Control.
• Move your W3 and W4 jumpers back to their original position (position 0), and reset your EVBU.
• At the HC12 prompt, examine the contents of memory starting at location 0x0D00 and verify that your program has been loaded into EEPROM.

After the code is in the EEPROM, you can run it in one of two ways - 1) From D-Bug 12, set the program counter to 0x0D00 and `g` (or `g 0D00`); or 2) Move jumper W3 to its other position (position 1), and reset or power-cycle the EVBU. (Note that if you run your program using method 2, you cannot easily re-enter D-Bug 12 to check the results of your program. We will use method 2 in later labs where we won't need to re-enter D-Bug 12 after starting a program.)

1.

Load your last program (which finds the lowest unsigned number) into EEPROM. Run it by giving the G 0D00 command from D-Bug 12. Verify that the performance is the same as when you ran it from RAM.

2.

Turn off power to your EVBU. Turn power back on, and rerun your program by giving the G 0D00 command from D-Bug 12. Verify that your program stayed in EEPROM.