Discussion
Assertion (A) : \(\mathrm{IO}/\overline{\mathrm{M}}\) pin is used to access memory.
Reason (R) : In memory mapped I/O the input/output ports are accessed as memory.
Answer: B
Both (A) and (R) are true but (R) is not the correct explanation of (A).
In the 8085, the \(\mathrm{IO}/\overline{\mathrm{M}}\) signal tells the system whether the current cycle is an I/O or a memory operation: low for memory, high for I/O. So it is used when accessing memory, and the assertion is true.
The reason is also true: in memory-mapped I/O the ports are given memory addresses and are accessed with memory instructions. But that is a different scheme. In memory-mapped I/O this pin is not needed to tell ports from memory, so the reason does not explain why the pin exists.
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