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Module 3: Instruction Set and Programming

20232m

Which of the following statement is true for the instruction PUSH B?
(i) It is an arithmetic instruction
(ii) Executes in single machine cycle
(iii) It reads from memory location
(iv) It performs memory write operation

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Answer: (iv) It performs memory write operation

Explanation: PUSH B (push register B onto stack) increments SP then writes B to internal RAM at [SP]. So it is a memory write, not read, not arithmetic. It takes 2 machine cycles (24 oscillator periods) on 8051, not single. It uses direct addressing for B but stack operation is indirect via SP. Hence only (iv) is true.

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