MICROPROCESSOR AND MICROCONTROLLER

Detailed explanation-1: -Answer: d Explanation: The control word register contents are used for i) initialising the operating modes (mode 0-mode 4) ii) selection of counters (counter0-counter2) iii) choosing binary or BCD counters iv) loading of the counter registers.

Detailed explanation-2: -Explanation: There are three counters that can be used as either counters or delay generators. Explanation: The control word register can only be written and cannot be read.

Detailed explanation-3: -Control Word Register: This register of 8254 programmable interval timer gets selected when A0=1 and A1=1. It is used to specify the BCD or binary counter to be used, its mode of operation and the data transfer to be used i.e read or write the data bytes.

Detailed explanation-4: -IOWR (active low) operation means writing data to an output device and not an input device. If the output port is to source large currents, the port lines must be buffered. So, the latch is used as it acts as good output port. More current should not be sourced or sinked from data lines while reading to avoid loading.

Detailed explanation-5: -Control Word Register It is used to write a command word, which specifies the counter to be used, its mode, and either a read or write operation.