EE 308 - LAB 3

Final version for 2001

Assembly Language Programming

Introduction and Objectives

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

Make sure you have the programs clearly thought out and written down before you come to lab. You should put all your code starting at memory location 0x0800. You are encouraged to bring the programs in on disk.

The Lab

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.

Write and run the following programs:

Write a program which writes an 0xff to address 0x0002, and then increments address 0x0000 indefinitely. (Note: this is a very short 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 PA lines are toggling.)

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. 7.)

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

  0 1 2 3 4 5 6 7 8 9 A B C D E F
000 00 01 02 03 04 05 06 07 08 09 0A 0B 0C 0D 0E 0F
001 10 11 12 13 14 15 16 17 18 19 1A 1B 1C 1D 1E 1F

Write a program to determine the number of non-negative numbers in a table. The starting address of the table is 0xa000 and the ending address is 0xdfff. Each element in the table should be considered to be an eight-bit signed number. Save the answer at address 0x0900. (This is a problem from the homework due feb. 9.)

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

Write a program that puts the largest one-byte unsigned number from memory locations 0xFCE0 through 0xFCFF in accumulator A and memory location 0x0900. (Note: The largest one-byte unsigned number is 0xff = 25510.) Test your program on the simulator and EVBU.

Loading Programs into EEPROM

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. Also, modify your LKF link file to start the .text section 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.

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, 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 running a program.)

Load your last program (which finds the highest 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.

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.

Bill Rison