Question

Why MOVX instruction is being used to access the ports of the 8255?

(a) because 8255 is connecting a microcontroller in memory mapped I/O configuration

(b) because 8255 is used to access the external communication

(c) because 8255 is used to access the data transfer

(d) because 8255 is used to access the interfacing of LCD, motor etc

The question was posed to me in an online interview.

My doubt is from Interfacing with 8255 topic in section AVR Microcontroller of Microcontroller

Answer 1

Right choice is (a) because 8255 is connecting a microcontroller in memory mapped I/O configuration

The explanation is: As 8255 is connecting a microcontroller in memory mapped I/O configuration. This means that memory space used to access 8255 (i.e. 8255 is treated as external memory). MOVX instruction is used to access external memory locations.