Which of the following sequences of AVR assembly language instructions would mak

Question

Which of the following sequences of AVR assembly language instructions would make a suitable interrupt service routine which reads a byte from IO register PINA, negates it (two's complement) and outputs the value to PORIC? (The values in the status register and all general purpose registers must be preserved.) a. .def temp = x16 int0: in temp, PORTA com temp out. PORTC, temp reti -def temp - x16 int0: push temp push SREG in temp, PINA neg temp out PORTC. temp pop STREO pop temp reti C. .def temp = r16 int0: in temp, SREG push SREG push temp in temp, PINA neg temp out PORTC, temp pop temp pop temp out SREG, temp reti d. .def temp = r16 int0: push temp in temp, SREG push temp in temp, PINA com temp out PORTC, temp pop temp out SREG, temp pop temp ret e. None of the above

Explanation / Answer

Ans: b

.def temp = r16 ; Define (register) Assign name- temp to register r16

int0: push temp ; External Interrupt 0

push SREG ; store SREG in stack

in temp, PINA ; loads data from pina to temp

neg temp ; find two's complement and save in temp

out PORTC,temp ; outputs temp to PORT C

POP SREG ; loads SREG with stack

POP temp ; loads temp with stack

reti

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