Question

The Registers A and C of 8085 contain the data E2H and 47H. What will be the contents of Accumulator in Hex digits after execution of each of the following instructions independently?

1) SUB C

2) XRA C

3) ADD C

Answer 1

1) [A] =E2H

[C] = 47JH

Instruction:SUB C

[C] = 47H = 0100 0111

2’s complement of 47H is : 1011 1001 i.e. [B9H]

After Execution: [A] =  9BH

   Carry [CY] = 00H

2) XRA C

∴ After execution : [A] = A5H

3) ADD C

∴ After executing : [A] = A9H

   Carry [C_Y] = 01H