;-------------------------------------------------------------------------------
; MSP430 Assembler Code Template for use with TI Code Composer Studio
;
;
;-------------------------------------------------------------------------------
            .cdecls C,LIST,"msp430.h"       ; Include device header file
            
;-------------------------------------------------------------------------------
            .def    RESET                   ; Export program entry-point to
                                            ; make it known to linker.

            .data
myStr:      .cstring "6*8"                  ; define string
;-------------------------------------------------------------------------------
            .text                           ; Assemble into program memory.
            .retain                         ; Override ELF conditional linking
                                            ; and retain current section.
            .retainrefs                     ; And retain any sections that have
                                            ; references to current section.

;-------------------------------------------------------------------------------
RESET       mov.w   #__STACK_END,SP         ; Initialize stackpointer
StopWDT     mov.w   #WDTPW|WDTHOLD,&WDTCTL  ; Stop watchdog timer


;-------------------------------------------------------------------------------
; Main loop here
;-------------------------------------------------------------------------------
main:      mov.w #myStr, R4                ; Move the starting address of myStr into register 4
		   clr.b  R5					   ; Use R5 to hold the character
		   clr.b  R6					   ; use r6 for first number
		   clr.b  R7					   ; use R7 for second
		   mov.b  #0, R3				   ; use r3 as counter
		   mov.b  @R4+, R5                 ; get a new character
		   cmp.b  #58, R5                  ; check for ':' character
		   jge    error					   ; if equal or greater, jump to error
		   cmp.b  #48, R5				   ; is it a '0'
		   jl     error					   ; if less, jump to error
		   mov.b  R4, R6				   ; move first number into Register 6
		   mov.b  @R4+, R5                 ; get a new character
		   cmp    #'*', R5				   ; is it '*'
		   jne    error					   ; if not equal, jump to error
		   mov.b  @R4+, R5				   ; get next character
		   cmp.b  #58, R5                  ; check for ':' character
		   jge    error					   ; if equal or greater, jump to error
		   cmp.b  #48, R5				   ; is it a '0'
		   jl     error					   ; if less, jump to error
		   mov.b  @R4+, R5				   ; get next char
		   cmp.b  #0, R5				   ; is it NULL
		   jne    error					   ; error if not
		   mov.b  R4, R7				   ; move next number to register 7
		   cmp.b  R7, R5				   ; which is less
		   jge    firstNum				   ; if first is greater jump to firstNum
		   jl	  secondNum				   ; less than, jump to secondNum

firstNum:  cmp    R3, R5				   ; comparing r3 to loop top
		   jz     endOne				   ; when 0 end loop
		   dadd.b   R7, R7				   ; add bigger number to itself
		   dadd.b  r3,r3				 	   ; increment counter
		   jmp    firstNum				   ; jump to firstNum

secondNum: cmp    R3, R7				   ; comparing r3 to loop top
		   jz     endTwo				   ; when 0 end loop
		   dadd.b   R5, R5				   ; add bigger number to itself
		   dadd.b    r3,r3				 	   ; increment counter
		   jmp    secondNum				   ; jump to secondNum
error:     mov    #0xFF, &P2OUT		   ; move FF to P2OUT
		   jmp 	  errorEnd

endOne:    mov.w   R7,&P2OUT               ; Write result in P1OUT (not visible on port pins)
endTwo:	   mov.w   R5,&P2OUT               ; Write result in P1OUT (not visible on port pins)
errorEnd:
           bis.w   #LPM4, SR               ; LPM4
           nop                             ; Required only for debugger

;-------------------------------------------------------------------------------
; Stack Pointer definition
;-------------------------------------------------------------------------------
            .global __STACK_END
            .sect   .stack
            
;-------------------------------------------------------------------------------
; Interrupt Vectors
;-------------------------------------------------------------------------------
            .sect   ".reset"                ; MSP430 RESET Vector
            .short  RESET