GATE CS 2000 Q1.7 — Machine Instructions and Addressing Modes

In the 8085 microprocessor, the READY input pin is used to synchronize slower memory or I/O devices with the faster CPU:

• If the READY input is high (logic 1), it indicates that the external device is ready for data transfer, and the microprocessor proceeds with normal execution.
• If the READY input is low (logic 0), the microprocessor enters a wait state ($T_{\text{wait}}$) and suspends its operation, holding the current state until the READY signal goes high.

Therefore, to put the 8085 microprocessor in the wait state, we must lower the READY input.

Why other options are incorrect:

• The HOLD pin is used for Direct Memory Access (DMA) requests. Raising the HOLD input asks the CPU to relinquish control of the address and data buses, which is different from entering a wait state for slow memory/IO synchronization.