Question

Consider the following statements:

1. Auxiliary carry flag is used only by the DAA and DAS instructions

2. Zero flag is set to 1 if the two operands compared are equal

3. All conditional jumps are long-type jumps

Which of the above statements are correct?
1. 1, 2 and 3
2. 1 and 2 only
3. 1 and 3 only
4. 2 and 3 only

Answer 1

Correct Answer - Option 2 : 1 and 2 only

LJMP (long jump): It is a 3-byte instruction in which the first byte represents opcode, and the second and third bytes represent the 16-bit address of the target location.

SJMP (short jump): It is a 2-byte instruction where the first byte is the opcode and the second byte is the relative address of the target location. The relative address ranges from 00H to FFH.

All conditional jumps are short jumps because they are 2-byte instructions.

Let two operands A and B are compared, if

• A = B, zero flag (Z) is set to 1
• A > B, sign flag (S) is reset to 0
• A < B, sign flag (S) is set to 1

 

Auxiliary Carry Flag (AC): It is set if a carry is generated out of the lower nibble. It is used only in 8-bit operations like DAA and DAS.