Intel 80C188XL, 80C186XL Repeat While Equal, Repeat While Zero, Repeat While Not Equal

INSTRUCTION SET DESCRIPTIONS

Table C-4. Instruction Set (Continued)

Name	Description	Operation	Flags
			Affected
REP	Repeat:	do while (CX) ≠ 0	AF –
REPE	Repeat While Equal:	service pending interrupts (if any)	CF –
REPZ	Repeat While Zero:	execute primitive string	DF –
REPNE	Repeat While Not Equal:	Operation in succeeding byte	IF –
REPNZ	Repeat While Not Zero:	(CX) ← (CX) – 1	OF –
	Controls subsequent string instruction	if	PF –
		primitive operation is CMPB,	SF –
	repetition. The different mnemonics
		CMPW, SCAB, or SCAW and	TF –
	are provided to improve program
		(ZF) ≠ 0	ZF –
	clarity.
		then
	REP is used in conjunction with the
		exit from while loop
	MOVS (Move String) and STOS (Store
	String) instructions and is interpreted
	as "repeat while not end-of-string" (CX
	not 0).
	REPE and REPZ operate identically
	and are physically the same prefix byte
	as REP. These instructions are used
	with the CMPS (Compare String) and
	SCAS (Scan String) instructions and
	require ZF (posted by these instruc-
	tions) to be set before initiating the
	next repetition.
	REPNE and REPNZ are mnemonics
	for the same prefix byte. These
	instructions function the same as
	REPE and REPZ except that the zero
	flag must be cleared or the repetition is
	terminated. ZF does not need to be
	initialized before executing the
	repeated string instruction.
	Instruction Operands:
	none

NOTE: The three symbols used in the Flags Affected column are defined as follows:

–the contents of the flag remain unchanged after the instruction is executed ¸? the contents of the flag is undefined after the instruction is executed

the flag is updated after the instruction is executed

C-37