Intel 80287, 80286 manual Rcl, Rcr, Rol, Ror

THE 80286 INSTRUCTION SET

RCLI RCR I ROLl ROR-Rotate Instructions

Opcode			Instruction		Clocks-N°	Description
00	/2		RCL	eb,1	2,mem=7	Rotate 9-bits (CF, EA byte) left once
02	/2		RCL	eb,CL*	5,mem=8	Rotate 9-bits (CF, EA byte) left CL times
CO	/2	db	RCL	eb,db*	5,mem=8	Rotate 9-bits (CF, EA byte) left db times
01	/2		RCL	ew,1	2,mem=7	Rotate 17-bits (CF, EA word) left once
03	/2		RCL	ew,CL*	5,mem=8	Rotate 17-bits (CF, EA word) left CL times
C1	/2	db	RCL	ew,db*	5,mem=8	Rotate 17-bits (CF, EA word) left db times
00	/3		RCR	eb,1	2,mem=7	Rotate 9-bits (CF, EA byte) right once
02	/3		RCR	eb,CL*	5,mem=8	Rotate 9-bits (CF, EA byte) right CL times
CO	/3	db	RCR	eb,db*	5,mem=8	Rotate 9-bits (CF, EA byte) right db times
01	/3		RCR	ew,1	2,mem=7	Rotate 17-bits (CF, EA word) right once
03	/3		RCR	ew,CL*	5,mem=8	Rotate 17-bits (CF, EA word) right CL times
C1	/3	db	RCR	ew,db*	5,mem=8	Rotate 17-bits (CF, EA word) right db times
00	/0		ROL	eb,1	2,mem=7	Rotate 8-bit EA byte left once
02	/0		ROL	eb,CL*	5,mem=8	Rotate 8-bit EA byte left CL times
CO	/0	db	ROL	eb,db*	5,mem=8	Rotate 8-bit EA byte left db times
01	/0		ROL	ew,1	2,mem=7	Rotate 16-bit EA word left once
03	/0		ROL	ew,CL*	5,mem=8	Rotate 16-bit EA word left CL times
C1	/0	db	ROL	ew,db*	5,mem=8	Rotate 16-bit EA word left db times
00	/1		ROR	eb,1	2,mem=7	Rotate 8-bit EA byte right once
02	/1		ROR	eb,CL*	5,mem=8	Rotate 8-bit EA byte right CL times
CO	/1	db	ROR	eb,db*	5,mem=8	Rotate 8-bit EA byte right db times
01	/1		ROR	ew,1	2,mem=7	Rotate 16-bit EA word right once
03	/1		ROR	ew,CL*	5,mem=8	Rotate 16-bit EA word right CL times
C1	/1	db	ROR	ew,db*	5,mem=8	Rotate 16-bit EA word right db times

* Add 1 clock to the times shown for each rotate made

FLAGS MODIFIED

Overflow (only for single rotates), carry

FLAGS UNDEFINED

Overflow for multi-bit rotates

OPERATION

Each rotate instruction shifts the bits of the register or memory operand given. The left rotate instruc- tions shift all of the bits upward, except for the top bit, whIch comes back arounu LU illt, uuliuiii. The right rotate instructions do the reverse: the bits shift downward, with the bottom bit coming around to the top.

For the RCL and RCR instructions, the carry flag is part of the rotated quantity. RCL shifts the carry flag into the bottom bit and shifts the top bit into the carry flag; RCR shifts the carry flag into the top bit and shifts the bottom bit into the carry flag. For the ROL and ROR instructions, the original value of the carry flag is not a part of the result; nonetheless, the carry flag receives a copy of the bit that was shifted from one end to the other.

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