EL - 262 / E1 Fall 2001

Introduction to Microprocessors and Microassembly Programming

Professor: Case

Submitted By:

Andrew Buettner

Lab #2: Addressing Modes, Branching, and the ASM Command

Thursday, March 06, 2003

Table Of Contents

1) Cover Page...............................1

2) Table of Contents.....................2

3) Objective..................................3

4) Components Used....................4

5) Procedures................................4

6) Lab Data / Results.....................5

1) Table 1...........................................5

2) Table 2...........................................5

3) Table 3...........................................5

4) Table 4...........................................5

5) Table 5...........................................6

6) Table 6...........................................6

7) Table 7...........................................6

8) Table 8...........................................6

9) Table 9...........................................6

10) Table 10........................................6

11) Table 11........................................7

12) Table 12........................................7

13) Table 13........................................7

14) Table 14........................................7

15) Table 15........................................7

16) Table 16........................................7

17) Table 17........................................8

18) Table 18........................................8

19) Table 19........................................8

20) Table 20........................................8

21) Table 21........................................8

22) Table 22........................................8

23) Table 23........................................9

24) Table 24........................................9

25) Table 25........................................9

26) Table 26........................................9

27) Table 27........................................9

28) Table 28......................................10

Table Of Contents (Continued)

29) Table 29......................................10

30) Table 30......................................10

31) Table 31......................................10

32) Table 32......................................10

33) Table 33......................................10

34) Table 34.......................................11

7) Answers to Lab Questions.......11

8) Conclusions.............................12

9) Attachments.............................12

Objective

The objective of this lab is to learn how to use the ASM command on the 68HC11 for on line assembly of programs. Additionally, to learn the syntax of the various branch commands to control program flow. Lastly to be able to write code that involves various branch commands and to use the Trace command to observe command - level program flow.

Components Used

1) Computer station with connected BUFFALO client. #D

Procedures

1) Bring the stations up.

2) Using MM set the following stack into memory at &HB600: 45, 56, 65, 76, 87, AB

3) Using RM set the IX register to &HB600, and the program counter to &H0100

4) Using MM set the following stack into &H0100: F6, B6, 02.

5) Use STOPAT to execute the code, record results.

6) Use RM to set the program counter back to &H0100 and IX to &HB600

7) Use the ASM program to enter the following code after the current stack:

a) LDX #B602

b) LDX B602

c) LDAA 3,X

d) LDX 4,X

e) STX B604

f) STX 3,X

8) Record Stack

9) Using MM enter the following stack at &H0100 B6, B6, 00, BB, B6, 01, B7, 01, 0C, 7E, 01, 20

10) Store at memory &H1020: 7E, 01, 00

11) Use the Trace (T) command to step through the code and observe results.

12) Set the program counter to &H0100

13) Load the following into stack at &H0100: B6, B6, 03, 81, 76, 27, F9, 7E, 01, 07

14) Trace the program's execution and note results.

15) Change &H0104 to something other than 76 and repeat step 14.

Lab Data / Results

1) Table 1: Stack of &HB600 Before Program Execution

	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
B60x	45	56	65	76	87	AB	23	12	5D	28	50	10	2A	A7	0D	B1
B61x	00	00	00	00	00	00	00	00	00	00	00	00	00	00	00	00
B62x	00	00	00	00	00	00	00	00	FF	FF	FF	FF	FF	FF	FF	FF

2) Table 2: Stack of &H0100 Before Program Execution

010x

011x

012x

013x

014x

015x

016x

017x

018x

3) Table 3: Registers Before Program Execution

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	B600	FF	FF	D0	0041

4) Table 4: Stack After Program Execution (&H0100)

010x

011x

012x

013x

014x

015x

016x

017x

018x

5) Table 5: Stack After Program Execution (&HB600)

	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
B60x	45	56	65	76	87	AB	23	12	5D	28	50	10	2A	A7	0D	B1
B61x	00	00	00	00	00	00	00	00	00	00	00	00	00	00	00	00
B62x	00	00	00	00	00	00	00	00	FF	FF	FF	FF	FF	FF	FF	FF

6) Table 6: Registers After Program Execution

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0103	FFFF	B600	FF	65	D0	0041

7) Table 7: Stack for Step 7 Before any Trace

010x

011x

012x

013x

014x

015x

016x

017x

018x

8) Table 8: Registers Before Trace

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	B600	FF	FF	D0	0041

9) Table 9: Registers After First Trace *Note: If Stack is unlisted, no change occurred*

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0103	FFFF	B602	FF	FF	98	0041

10) Table 10: Registers After Trace 2

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0106	FFFF	6576	FF	FF	90	0041

11) Table 11: Registers After Trace 3

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0108	FFFF	6576	00	FF	94	0041

12) Table 12: Registers After Trace 4

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	010A	FFFF	0000	00	FF	94	0041

13) Table 13: Registers After Trace 5 *Stack does not change*

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	010D	FFFF	6576	00	FF	94	0041

14) Table 14: Registers After Trace 6 *Stack does not change*

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	010F	FFFF	6576	00	FF	94	0041

15) Table 15: Stack for Trace / Jump Operation

010x

011x

012x

013x

014x

015x

016x

017x

018x

16) Table 16: Registers Before Trace Operations

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	0000	00	FF	94	0041

17) Table 17: Registers After Trace 1

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0103	FFFF	0000	45	FF	90	0041

18) Table 18: Registers After Trace 2

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0106	FFFF	0000	9B	FF	9A	0041

19) Table 19: Registers After Trace 3

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0109	FFFF	0000	9B	FF	98	0041

20) Table 20: Stack After Trace 3 Illustrating Changes

010x

011x

012x

013x

014x

015x

016x

017x

018x

21) Table 21: Registers After Trace 4

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0120	FFFF	0000	9B	FF	98	0041

22) Table 22: Registers After Trace 5

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0109	FFFF	0000	9B	FF	98	0041

23) Table 23: Registers After Trace 6

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	0000	9B	FF	98	0041

24) Table 24: Registers After Trace 7

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0103	FFFF	0000	45	FF	90	0041

*Note: This is the same as the first step and returns to repeat at that point*

25) Table 25: Stack for Compare Program

010x

011x

012x

013x

014x

015x

016x

017x

018x

B60x

B61x

B62x

26) Table 26: Registers Before Compare Program

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	0000	45	65	90	0041

27) Table 27: Registers After Trace 1

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0103	FFFF	0000	76	65	90	0041

28) Table 28: Registers After Trace 2

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0105	FFFF	0000	76	65	94	0041

29) Table 29: Registers After Trace 2

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	0000	76	65	94	0041

*Note: This is identical to the initial trace and loops to that point*

30) Table 30: Stack With Altered &HB603 Value

010x

011x

012x

013x

014x

015x

016x

017x

018x

B60x

B61x

B62x

31) Table 31: Registers Before Trace Operations

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0100	FFFF	0000	76	65	94	0041

32) Table 32: Registers After First Trace

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0103	FFFF	0000	70	65	90	0041

33) Table 33: Registers After Trace 2

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0105	FFFF	0000	70	65	99	0041

34) Table 34: Registers After Trace 3 and All Subsequent Traces

Register:	PC	IY	IX	AA	AB	CCR	SP
Value:	0107	FFFF	0000	70	65	99	0041

Answers to Lab Questions

1) Q: Write code that will place the smallest number (Unsigned Binary) of a stack in &HB600 - &HB606 into memory location &H01C0.

A: 1) 0100 LDAB #$FF

2) 0102 LDX #$B600

3) 0105 STAB $01C0

4) 0108 INCB

5) 0109 CMPB #06

6) 010B BGT $0121

7) 010D LDY #B600

8) 0111 ABY

9) 0113 LDAA 0,Y

10) 0116 CMPA $01C0

11) 0119 BHI $0108

12) 011B STAA $01C0

13) 011E JMP $0108

14) 0121 STOP

2) Q: Write code that will place the smallest number (Signed Binary) of a stack in &HB600 - &HB606 into memory location &H01C0.

A: 1) 0100 LDAB #$FF

2) 0102 LDX #$B600

3) 0105 STAB $01C0

4) 0108 INCB

5) 0109 CMPB #06

6) 010B BGT $0121

7) 010D LDY #B600

8) 0111 ABY

9) 0113 LDAA 0,Y

10) 0116 CMPA $01C0

11) 0119 BGT $0108

12) 011B STAA $01C0

13) 011E JMP $0108

14) 0121 STOP

Conclusions

From this lab it is shown that ASM can be used to enter code using the 68HC11's assembly language, instead of directly programming it with machine code. Additionally the Trace command was observed as it stepped through the program code. Also, the various branching instructions were implemented and produced the correct results. Through this lab I learned the syntax of the ASM command (ASM <starting address>). Also I stepped through the code produced by step seven to prove that the stack at &HB600 did not change even though the command was a write. I believe that the reason for the no change condition is because the memory locations specified are EEPROM memories, and can not be directly written to. The results from that trace consist of tables 7 - 14. Another problem that was encountered was the fact that B could not be added to X to form an address. I discovered this problem while working with the two lab questions. In order to compensate for this problem, I used Y as a temporary register and added B to it, then used that as the stack point address. This workaround successfully solved the problem and the submitted code in this lab performed optimally. Other than that there were no other problems with this lab.

Attachments

Original lab handout
Original lab data
Calculations