Datasheet

Instruction Set Description

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4.6.2.37 RETI

RETI Return from interrupt

RETI

Syntax

Operation @SP → SR.15:0 Restore saved SR with PC.19:16

SP + 2 → SP

@SP → PC.15:0 Restore saved PC.15:0

SP + 2 → SP Housekeeping

Description

The SR is restored to the value at the beginning of the interrupt service routine. This

includes the four MSBs of the PC.19:16. The SP is incremented by two afterward.

The 20-bit PC is restored from PC.19:16 (from same stack location as the status bits)

and PC.15:0. The 20-bit PC is restored to the value at the beginning of the interrupt

service routine. The program continues at the address following the last executed

instruction when the interrupt was granted. The SP is incremented by two afterward.

Status Bits N: Restored from stack

C: Restored from stack

Z: Restored from stack

V: Restored from stack

Mode Bits OSCOFF, CPUOFF, and GIE are restored from stack.

Example Interrupt handler in the lower 64KB. A 20-bit return address is stored on the stack.

INTRPT PUSHM.A #2,R14 ; Save R14 and R13 (20-bit data)

... ; Interrupt handler code

POPM.A #2,R14 ; Restore R13 and R14 (20-bit data)

RETI ; Return to 20-bit address in full memory range

200

CPUX SLAU144J–December 2004–Revised July 2013

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