Question

Which of the following combination is the best to enable the external hardware interrupt 0 of the IE register (assuming initially all bits of the IE register are zero)?

(a) EX0=1

(b) EA=1

(c) any of the mentioned

(d) EX0=1 & EA=1

This question was posed to me in class test.

My question is from Interrupt Programming topic in section 8051 Microcontroller of Microcontroller

Answer 1

The correct choice is (d) EX0=1 & EA=1

To explain I would say: For executing the EX0 interrupt, the EX0 and EA bits of the IE register should be set. EA is set to enable all the interrupts and EX0 is set to enable the external hardware interrupt 0 interrupt and mask the other enabled interrupts.