Z8 Microcontrollers
Instruction Descriptions and Formats ZiLOG
12-34 UM001601-0803
IRET
INTERRUPT RETURN
IRET
Interrupt RETURN
IRET
Instruction Format:
Operation:
FLAGS <— @SP
SP <— SP + 1
PC <— @SP
SP <— SP + 2
IMR (7) <— 1
This instruction is issued at the end of an interrupt service routine. It restores the Flag Register (Control Register
FCH) and the PC. It also re-enables any interrupts that are potentially enabled.
Example:
If Stack Pointer Low Register FFH currently contains the value 45H, Register 45H contains the value 00H, Register
46H contains 6FH, and Register 47 Contains E4H, the statement:
IRET
Op Code: BF
restores the FLAG Register FCH with the value 00H, restores the PC with the value 6FE4H, re-enables the
interrupts, and sets the Stack Pointer Low to 48H. The next instruction to be executed will be at location 6FE4H.
Flags: C: Restored to original setting before the interrupt occurred.
Z: Restored to original setting before the interrupt occurred.
S: Restored to original setting before the interrupt occurred.
V: Restored to original setting before the interrupt occurred.
D: Restored to original setting before the interrupt occurred.
H: Restored to original setting before the interrupt occurred.
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