8051 flag bits and program status word register(PSW)

                   PSW(Program status word) Register is to observe the bit level manipulations takes place in any arithmetic calculation.

PSW Register at Bit Level Description:

Register banks used in 8051:

1    1. The flag register in the 8051 is called PSW(Program Status Word)

2    2. What is the size of flag register in 8051?                               Ans:8-bits

3    3. Which bits of the PSW register are user-definable?       Ans: PSW.5, PSW.4, PSW.3

4    4. Find the Carry(CY) and Auxiliary carry(AC) flag bits for the following?

                        MOV A,#0FFH

                        ADD A,#01

Ans:   CY=1 and AC=1

1     5. Find the Carry(CY) and Auxiliary carry(AC) flag bits for the following?

                        MOV A,#0C2H

                        ADD A,#3DH

Ans:       CY=0                                      AC=0

Categories: embedded programming