Intel 80287 manual Rep Ins, REP Insb, REP Insw, REP Movsb, REP Movsw, REP Outsb, REP Outsw

THE 80286 INSTRUCTION SET

REP IREPE/REPNE-Repeat Following. String Operation

Opcode		Instruction								Clocks·	Description
F3	6C	REP	INS			eb,OX				5+4*CX	Input CX bytes from port OX into ES:[OI]
F3	60	REP	INS			ew,OX				5+4*CX	Input CX words from port OX into ES:[OI]
F3	6C	REP	INSB							5+4*CX	Input CX bytes from port OX into ES:[OI]
F3	60	REP	INSW					mb,mb		5+4*CX	Input CX words from port OX into ES:[OI]
F3	A4	REP	MOVS							5+4*CX	Move CX bytes from [SI] to ES:[OI]
F3	A5	REP	MOVS					mW,mw		5+4*CX	Move CX words from [SI] to ES:[OI]
F3	A4	REP	MOVSB							5+4*CX	Move CX bytes from OS:[SI] to ES:[OI]
F3	A5	REP MOVSW								5+4*CX	Move CX words from OS:[SI] to ES:[OI]
F3	6E	REP OUTS					OX,eb			5+4*CX	Output CX bytes from [SI] to port OX
F3	6F	REP OUTS					OX,ew			5+4*CX	Output CX words from [SI] to port OX
F3	6E	REP OUTSB								5+4*CX	Output CX bytes from OS:[SI] to port OX
F3	6F	REP OUTSW								5+4*CX	Output CX words from OS:[SI] to port OX
F3	AA	REP	STOS				mb			4+3*CX	Fill CX bytes at ES:[OI] with AL
F3	AB	REP STOS					mw			4+3*CX	Fill CX words at ES:[OI] with AX
F3	AA	REP	STOSB							4+3*CX	Fill CX bytes at ES:[OI] with AL
F3	AB	REP STOSW								4+3*CX	Fill CX words at ES:[OI] with AX
F3	A6	REPE		CMPS				mb,mb		5+9*N	Find nonmatching bytes in ES:[OI] and [SI]
F3	A7	REPE		CMPS				mW,mw		5+9*N	Find nonmatching words in ES:[OI] and [SI]
F3	A6	REPE		CMPSB						5+9*N	Find nonmatching bytes in ES:[OI] and OS:[SI]
F3	A7	REPE		CMPSW						5+9*N	Find nonmatching words in ES:[OI] and OS:[SI]
F3	AE	REPE		SCAS				mb		5+S*N	Find non-AL byte starting at ES:[OI]
F3	AF	REPE		SCAS				mw		5+S*N	Find non-AX word starting at ES:[OI]
F3	AE	REPE		SCASB						5+S*N	Find non-AL byte starting at ES:[OI]
F3	AF	REPE SCASW							mb,mb	5+S*N	Find non-AX word starting at ES:[OI]
F2	A6	REPNE			CMPS					5+9*N	Find matching bytes in ES:[OI] and [SI]
F2	A7	REPNE			CMPS				mW,mw	5+9*N	Find matching words in ES:[OI] and [SI]
F2	A6	REPNE			CMPSB					5+9*N	Find matching bytes in ES:[OI] and OS:[SI]
F2	A7	REPNE CMPSW								5+9*N	Find matching words in ES:[OI] and OS:[SI]
F2	AE	REPNE			SCAS				mb	5+S*N	Find AL, starting at ES:[OI]
F2	AF	REPNE			SCAS				mw	5+S*N	Find AX, starting at ES:[OI]
F2	AE	REPNE			SCASB					5+S*N	Find AL, starting at ES:[OI]
F2	AF	REPNE			SCASW					5+S*N	Find AX, starting at ES:[OI]

* N denotes the number of iterations actually executed.

FLAGS MODIFIED

By CMPS and SCAS, none by REP

FLAGS UNDEFINED

None

OPERATION

REP, REPE, and REPNE are prefix operations. These prefixes cause the string instruction that follows to be repeated CX times or (for REPE and REPNE) until the indicated condition in the zero flag is no longer met. Thus, REPE stands for "Repeat while equal," REPNE for "Repeat while not equal."

B-92