Zilog Z80380 - Manual (Page 177)

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Z380 ™
U SER ' S M ANUAL Z ILOG
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