Zilog Z80380 Manual do Utilizador descarregar pdf (Página 177)

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Z380

™

USER'S MANUAL

ZILOG

DC-8297-03

RETN

RETURN FROM NONMASKABLE INTERRUPT

RETN

Operation: if (XM) then begin

PC(7-0) ← (SP)

PC(15-8) ← (SP+1)

PC(23-16) ← (SP+2)

PC(31-24) ← (SP+3)

SP ← SP + 4

end

else begin

PC(7-0) ← (SP)

PC(15-8) ← (SP+1)

SP ← SP + 2

end

IEF1 ← IEF2

This instruction is used to return to a previously executing procedure at the end of a

procedure entered by a nonmaskable interrupt. The contents of the location addressed by

the Stack Pointer (SP) are popped into the Program Counter (PC), thereby specifying the

location of the next instruction to be executed. The previous setting of the interrupt enable

bit is restored by execution of this instruction.

Flags: S: Unaffected

Z: Unaffected

H: Unaffected

V: Unaffected

N: Unaffected

C: Unaffected

Addressing Execute

Mode Syntax Instruction Format Time Note

RETN 11101101 01000101 2+r X

1 2 ... 172 173 174 175 176 177 178 179 180 181 182 ... 267 268

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Zilog Z80380 Manual do Utilizador Página 177