8051 Program - return length of string

; Description:
; DPTR Points To A String In External RAM To Determine The Length Of.
; The String Must Be 0 Terminated, And Less Than 256 Bytes In Length.
; The Length Is Returned In Acc.
;
; Entry Requirements:
; DPTR Points To An ETX Terminated String In External Memory
;
; On Exit:
; DPTR Points To ETX
; Acc Has Length Of String
;
; Affected:
; PSW.CY, PSW.Z, PSW.P, Acc
;
; Stack:
; 3 Bytes, Not Including Space Used By Called Routines
;
; Comments:
; If String Is Longer Than 255 Bytes, Acc Will Report Length Mod 256
;

	ETX equ 3	; ASCII ETX Character
UTIL_STRLEN:
	push b	; Save B
	push dph	; Save DPH
	push dpl	; Save DPL
	mov b,#0	; Clear Length Counter
		;
loop1:	movx a,@dptr	; Get Byte
	cjne a,#ETX,temp	; If ETX, End Found
temp:	jmp loop2	;
	inc dptr	; Next Location
	inc b	; Increment Length
	jmp loop1	; Repeat Until 0x00
		;
loop2:	mov a,b	; Get Length To A
	pop dpl	; Recover DPL
	pop dph	; Recover DPH
	pop b	; Recover B
	ret	; Return To Caller

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

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Related topics:
8051 Program - replace 0x00 with ETX in string   |   8051 Program - locate ETX in string   |   8051 Program - remove trailing spaces   |   8051 Program - memory subroutines   |   8051 Program - math subroutines   |   8051 Program - conversion subroutines

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List of topics: 8051

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