how can I write the assembly language to count on total number of characters of

Question

how can I write the assembly language to count on total number of characters of given string in assembly language?(relate MSP430)

#include "msp430.h"

ORG 0FF00h   

mystr DB "Welcome to Aeroclub Programming @JLC215!"

NAME main   

PUBLIC main   

ORG 0FFFEh

DC16 init   

RSEG CSTACK   

RSEG CODE   

init: MOV #SFE(CSTACK), SP

main: NOP   

MOV.W #WDTPW+WDTHOLD, &WDTCTL

BIS.B #0FFh, &P1DIR

BIS.B #0FFh, &P2DIR

MOV #mystr, R5

CLR.B R6   

CLR.B R7 store total character   

gonext: MOV.B @R5+, R6

CMP #0, R6

JEQ lend   

INC R7

CMP.B #'a', R6

CMP.B #'{', R6

JMP gonext

lend:   

MOV.B R7, &P2OUT   

BIS.W #LPM4, SR

NOP   

END

Explanation / Answer

#include "msp430.h" ; #define controlled include file

ORG 0FF00h

myStr DB "Welcome to Aeroclub Programming @JLC215!" ; the string is placed on the stack

; the null character is automatically added after the '!'

NAME main ; module name

PUBLIC main ; make the main label visible

; outside this module

ORG 0FFFEh

DC16 init ; set reset vector to 'init' label

RSEG CSTACK ; pre-declaration of segment

RSEG CODE ; place program in 'CODE' segment

init: MOV #SFE(CSTACK), SP ; set up stack

main: NOP ; main program

MOV.W #WDTPW+WDTHOLD,&WDTCTL ; Stop watchdog timer

BIS.B #0FFh,&P1DIR ; configure P1.x output

MOV.W #myStr, R4 ; load the starting address of the string into the

register R4

CLR.B R5 ; register R5 will serve as a counter

gnext: MOV.B @R4+, R6 ; get a new character

CMP #0,R6

JEQ lend ; go to the end

INC R5 ; increment counter

JMP gnext

lend: MOV.B R5,&P1OUT ; Set all P1 pins

BIS.W #LPM4,SR ; LPM4

NOP ; Required only for debugger

END

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