Assembly Language

Please refer to slides and Primer boards lessons

1. If the switch S7 of the input PORT0 connected to the data line D7 is at logic 1 and the other switches are at logic 0, specify the contents of the accumulator when the instruction IN PORT0 is executed.
   MVI A,9FH
   IN PORT0
   MOV B,A
   OUT PORT1
   HLT
2. Specify the output at PORT1 and the contents of the register B after executing the instructions in Problem #1.
3. Specify the register contents and the flag status as the following instructions are executed.
   A C S Z CY
   XX XX 0 0 0
   MVI A,5EH
   ADI A2H
   MOV C,A
4. Specify the register contents and the flag status as the following instructions are executed.
   A B S Z CY
   XX XX X X X
   SUB A
   MOV B,A
   DCR B
   INR B
   SUI 01H
5. Write a program to
   a. clear the accumulator
   b. add 47H (use ADI instruction)
   c. subtract 92H
   d. add 64H
   e. display the results after subtracting 92H and after adding 64H
6. Specify the register contents and the flag status as the following instructions are executed
   A B S Z CY
   XX XX 0 0 0
   XRA A
   MVI B,4AH
   SUI 4FH
   ANA B
7. What is the output at PORT1 when the following instructions are executed?
   MVI A,8FH
   ADI 72H
   JC DSPLAY
   OUT PORT1
   HLT
   DSPLAY: XRA A
   OUT PORT1
   HLT

Answers.

1. The data on A after the instruction IN PORT0 is executed will be the same as the data read on PORT0. Thus, the data on A will be equal to 80H.
2. The data on register A will be copied to register B. So, the data on register B will be 80H. After the instruction OUT PORT1, the data on Register A will be outputted in PORT1. Thus, PORT1 would also show 80H or 1000 0000.
3. A C S Z CY
   XX XX 0 0 0
   MVI A,5EH 5EH xx 0 0 0
   ADI A2H 00H xx 0 1 1
   MOV C,A 00H 00H 0 1 1
4. A B S Z CY
   XX XX X X X
   SUB A 00H XX 0 1 0
   MOV B,A 00H 00H 0 1 0
   DCR B 00H FFH 1 0 1
   INR B 00H 00H 0 1 0
   SUI 01H FFH 00H 1 0 1
5. SUB A
   ADI 47H
   SUI 92H
   OUT PORT0
   ADI 64H
   OUT PORT0
   HLT
6. A B S Z CY
   XX XX 0 0 0
   XRA A 00H XX 0 1 0
   MVI B,4AH 00H 4AH 0 1 0
   SUI 4FH C0H 4AH 1 0 1
   ANA B 40H 4AH 0 0 0
7. The Carry flag will be set after the instruction ADI 72H, so when the JC DISPLAY is executed it will jump to DISPLAY. XRA A will reset the accumulator. Thus, the output in PORT1 will be 00H.