;
; ***************************************************************************
; ***  Bubble Software Parallax to PIC Source Converter. Copyright 1999.  ***
; ***  http://www.picnpoke.com                 email: sales@picnpoke.com  ***
; ***************************************************************************
;
; QUALIFY table, string
; Reads a one-character Serin string and looks up the character in
; a table of "qualifiers." If the character matches the next qualifier,
; the routine increments a counter and checks to determine whether all
; qualifiers have been matched. If so, it returns a 1 in w. If not,
; it returns a 0 in w after resetting the counter to the first item in
; the qualifier list.

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

 org 8
qual Res d'1' ; Pointer to qualifiers.
buffer equ d'31' ; Serin string address.

 org 0

P_word       ADDWF pcl                  
             RETLW d'6'                 ; No. of elements in password.
             RETLW 'S'                  ; The password.
             RETLW 'e'
             RETLW 's'
             RETLW 'a'
             RETLW 'm'
             RETLW 'e'

; Below is a dummy Serin routine intended for use on the PSIM simulator.
; Wait until PSIM reaches the "ret" below, then change the data at buffer-1
; (hex address 1E). You can step through Qualify to see how it works.
; The password "Sesame" is 53h, 65h, 73h, 61h, 6Dh, 65h.

Serin        MOVLW 'A'                  ; Dummy Serin for demo.
             MOVWF buffer-1
             RETLW 0h                   ; Enter character data here.

start        MOVLW d'4'                 ; Input for serial data.
             TRIS 5h
             MOVLW d'0'                 ; All outputs for LEDs
             TRIS 6h
             CLRF 6h                    ; LEDs off to begin.
             CLRF qual                  ; Clear qual to start.

start_loop   CALL Serin                 ; Receive one byte.
             CALL Qualify               ; Check it against password.
             IORLW 0h                   ; IF w=1 THEN LEDs_on
             BTFSC status,z             ; ELSE :loop
             GOTO start_loop            
             MOVLW d'255'               ; Password match: toggle LEDs.
             XORWF 6h
             GOTO start                 ; Do it again.

; Upon entry, a one-byte Serin string should be stored at buffer-1.
; Qualify will check it against the next entry in the P_word table, and
; if there's a match, will increment the qualifier counter qual. If there's
; no match, it will clear qual, and check the character against the first
; entry in P_word. This second step prevents Qualify from failing to
; recognize passwords after a false start, like "SeSesame."

Qualify      INCF qual,w                ; Look up next item in P_word.
             CALL P_word                
              subwf buffer-1,0          ; Compare it to received byte by <Microchip instruction>
             BTFSS status,z             ; subtraction. If result <> 0, no match.
             GOTO Qualify_no_match
             INCF qual                  ; Match: increment qual pointer and
             CLRW                       ; get the 0th item in the table (number
             CALL P_word                ; of chars in the password).
              subwf qual,0              ; IF qual = no._of_P_word_chars THEN <Microchip instruction>
             BTFSC status,z             ; return with 1 in w.
             RETLW d'1'                 ; ELSE return with 0 in w.
             RETLW 0h                   
Qualify_no_match  MOVF qual             ; IF qual = 0, return with 0 in w.
             BTFSC status,z             
             RETLW 0h                   
             CLRF qual                  ; ELSE qual = 0: GOTO Qualify (check
             GOTO Qualify               ; char against 0th password entry).


             
             
             end