;
; ***************************************************************************
; ***  Bubble Software Parallax to PIC Source Converter. Copyright 1999.  ***
; ***  http://www.picnpoke.com                 email: sales@picnpoke.com  ***
; ***************************************************************************
;
; ASC_BIN numeric string
; This program converts a counted string of ASCII characters
; received by Serin into a 16-bit value in the variable n1.

	P = pic16c55
	#include <16c55.inc>   ; processor assembler definitions
	_CONFIG _xt_osc & _wdt_off & _protect_off
 reset start

buffer equ d'31' ; String buffer at end of memory
ASC_0 equ  '0'; ASCII chars for nos. are 30h thru 39h.

 org 8
dec_no Res d'1' ; Decade (1,10,100...) to work on.
n1H Res d'1' ; MSB of converted number.
n1L Res d'1' ; LSB of converted number.
n2H Res d'1' ; MSB of 16-bit temp variable.
n2L Res d'1' ; LSB of 16-bit temp variable.
temp Res d'1' ; Temporary storage

; Device data and reset vector
 org 0

decade       ADDWF pcl                  
             RETLW d'39'                
             RETLW d'16'
             RETLW d'3'
             RETLW d'232'
             RETLW d'0'
             RETLW d'100'
             RETLW d'0'
             RETLW d'10'
             RETLW d'0'
             RETLW d'1'

start        MOVLW d'0'                 ; Set ports to output.
             TRIS 6h
             MOVLW d'0'                 
             TRIS 7h
             MOVLW d'5'                 ; String count.
             MOVWF buffer
             MOVLW 0x36                 ; Numeric text: "65535."
             MOVWF buffer-1
             MOVLW 0x35                 ; To view the results of the
             MOVWF buffer-2
             MOVLW 0x35                 ; conversion, run this program
             MOVWF buffer-3
             MOVLW 0x33                 ; on the PSIM simulator, or merge
             MOVWF buffer-4
             MOVLW 0x35                 ; it with Serin.
             MOVWF buffer-5
             CALL ASC_BIN               
             MOVF n1L,w                 ; Show result on LEDs.
             MOVWF 6h
             MOVF n1H,w                 
             MOVWF 7h
             GOTO $                     ; Endless loop.

; ASC_BIN gets the value of each digit (0-9) of a numeric string. Depending
; on the number of digits in the string, it looks up the multiplier (10000, 1000,100,10, or 1) and adds that multiplier to n1 digit number of times.
ASC_BIN      CLRF n1H                   ; n1 = 0
             CLRF n1L                   
             MOVLW buffer-1             ; If the string is empty,
             MOVWF fsr
             MOVF buffer                ; return 0 in 16-bit answer
             BTFSS status,z             ; and error code (1) in
             GOTO ASC_BIN_loop
             RETLW d'1'                 ; w. Else, do the conversion.
ASC_BIN_loop MOVLW ASC_0                ; w = 30h (ASCII start point).
              subwf indirect,0          ; w = character_value-30h. <Microchip instruction>
             BTFSC status,z             
             GOTO ASC_BIN_next
             MOVWF temp                 ; temp = w
             MOVLW d'5'                 
             MOVWF dec_no
             MOVF buffer,w              ; dec_no = 5-string_length
             SUBWF dec_no
             BCF status,c               
             RLF dec_no                 ; dec_no = dec_no*2
             MOVF dec_no,w              
             CALL decade                ; Look up MSB of multiplier.
             MOVWF n2H                  ; Store it in MSB of n2.
             INCF dec_no,w              ; Look up the LSB of multiplier.
             CALL decade                
             MOVWF n2L                  ; Store it in LSB of n2.
ASC_BIN_add_it  CALL Add16              ; n1 = n1 + n2.
             DECFSZ temp                ; Repeat 1 to 9 times for each digit.
             GOTO ASC_BIN_add_it
ASC_BIN_next DECF fsr                   ; Get the next byte of the string.
             DECF buffer                ; Adjust string counter.
             BTFSS status,z             ; Any bytes left? Yes: loop.
             GOTO ASC_BIN_loop
             RETLW 0h                   ; No: return.
Add16        MOVF n2L,w                 ; Add the LSBs. If carry,
             ADDWF n1L
             BTFSC status,c             ; increment MSB of sum.
             INCF n1H                   
             MOVF n2H,w                 ; Add the MSBs.
             ADDWF n1H
             RETLW 0h                   

             
             
             end