Computer Hardware User's Guide

RETIcond

Return From Interrupt Conditionally

13-198

Syntax RETI

cond

Operation If

cond

is true:

*SP – – → PC

1 → ST (GIE).

Else, continue.

Operands None

Opcode

31 24 23 16 8 7 015

01111 0

0 00

cond

000 0000000000000

Description A conditional return is performed. If the condition is true, the top of the stack

is popped to the PC, and a 1 is written to the global interrupt enable (GIE) bit

of the status register. This has the effect of enabling all interrupts for which the

corresponding interrupt enable bit is a 1.

The ’C3x provides 20 condition codes that can be used with this instruction

(see Table 13–12 on page 13-30 for a list of condition mnemonics, condition

codes, and flags). Condition flags are set on a previous instruction only when

the destination register is one of the extended-precision registers (R7–R0) or

when one of the compare instructions (CMPF, CMPF3, CMPI, CMPI3, TSTB,

or TSTB3) is executed.

Cycles 4

Status Bits LUF Unaffected

LV Unaffected

UF Unaffected

N Unaffected

Z Unaffected

V Unaffected

C Unaffected

OVM Operation is not affected by OVM bit value.Mode Bit