Question

The IOR (active low) input line acts as output in

(a) slave mode

(b) master mode

(c) master and slave mode

(d) none of the mentioned

The question was asked in an internship interview.

The above asked question is from DMA Controller 8257 in portion DMA, Floppy Disk and CRT Controllers of Microprocessor

Answer 1

Right option is (b) master mode

The best I can explain: The IOR (active low) is an active low bidirectional tristate input line, that acts as input in the slave mode, and acts as output in the master mode. In master mode, this signal is used to read data from a peripheral during a memory write cycle.