8051 Program - rotate dptr left 4bits

; Description:

; Rotate DPTR 4 Bits To Left, Bit 15 Moves To Bit 0

;

; Entry Requirements:

; DPTR Has Value To Rotate Left

;

; On Exit:

; DPTR = ((DPTR & 0xf000) >> 12) | (DPTR << 4)

;

; Affected:

; PSW.CY, DPTR

;

; Stack:

; 2 Bytes, Not Including Space Used By Called Routines

;

; Comments:

; None

;

UTIL_DPTRROL4:
	push acc	; Save Acc
	push 0	; Save R0
	mov r0,#4	; Number Times To Shift
loop:	mov a,dph	; Get High Byte
	mov c,acc.7	; Get High Order Bit
	mov a,dpl	; Get Low Of DPTR
	rlc a	; Shift Left
	mov dpl,a	; Store Back To DPL
	mov a,dph	; Get High Of DPTR
	rlc a	; Shift Left
	mov dph,a	; Store Back To DPH
	djnz r0,loop	; Repeat For R0 Bytes
	pop 0	; Recover R0
	pop acc	; Recover Acc
	ret	; Return To Caller

Source: Assorted Utilities, John C. Wren 11/23/96

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List of topics: 8051

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