;--------------------------------------------------------------------
; This program is designed to check a cable with six wires


	list p=16c84, w=0, r=DEC
	include "p16c84.inc"


;--------------------------------------------------------------------
; Two macros that switch between register banks


bank_0		macro
		 bcf	STATUS, RP0
		endm

bank_1		macro
		 bsf	STATUS, RP0
		endm


;--------------------------------------------------------------------
; Program entry point is 0.
; Jump to "start" to avoid address 4.

	org 0
	lgoto start


;--------------------------------------------------------------------
; Address 4 is entry point for interupt routine.
; Maight be used later for flashing led...

	org 4
	retfie


;--------------------------------------------------------------------
; The macro "TEST" sets one of six output pins (RA[0..4] and RB6) 
; to low, the other five remain in high impedance mode. 
; Than it checks the six inputs (RB[0..5]) which have enabled 
; weak pull-ups.

TEST 	macro	outtris, outpin, in, short1, short2, short3, short4, short5
	 bank_1
	 bcf	outtris, outpin	; set test-output to low
	 bank_0

	 nop			; relax
	 nop

	 btfsc	PORTB, in	; check if line connected
	 goto	broken

	 btfss	PORTB, short1	; check if lines shortened
	 goto	short
	 btfss	PORTB, short2
	 goto	short
	 btfss	PORTB, short3
	 goto	short
	 btfss	PORTB, short4
	 goto	short
	 btfss	PORTB, short5
	 goto	short

	 bank_1
	 bsf	outtris, outpin	; set test-output back to high impedance
	 bank_0
	endm


;--------------------------------------------------------------------
; Some space for a possibly later inserted interupt routine

	org 0x100


;--------------------------------------------------------------------
; setupled configures RB6 and RB7 as output

setupled:
	bank_1
	movlw	0x3F
	movwf	TRISB
	bank_0
	return


;--------------------------------------------------------------------
; delay waits for about half a second

counter1	equ	0x11
counter2	equ	0x12

delay:	movlw	200
	movwf	counter1
outer:
	movlw	100
	movwf	counter2
inner:
	decfsz	counter2, F
	goto	inner
	decfsz	counter1, F
	goto	outer
	return


;--------------------------------------------------------------------
; The main program tests at program start the connection;
; than it displays the result until power down

start:	bank_1
	bcf	OPTION_REG, 7	; enable weak pull-ups of Port B
	movlw	0xff
	movwf	TRISA		; high impedance
	movwf	TRISB		; high impedance
	bank_0
	clrf	PORTA		; low output pegel
	clrf	PORTB		; low output pegel
	TEST	TRISA, 0,	0,	   1, 2, 3, 4, 5
	TEST	TRISA, 1,	1,	0,    2, 3, 4, 5
	TEST	TRISA, 2,	2,	0, 1,    3, 4, 5
	TEST	TRISA, 3,	3,	0, 1, 2,    4, 5
	TEST	TRISA, 4,	4,	0, 1, 2, 3,    5
	TEST	TRISB, 6,	5,	0, 1, 2, 3, 4

ok:	call	setupled
	bcf	PORTB, 6
	bsf	PORTB, 7
okloop:	
	nop
	goto	okloop


short:	call	setupled
shortloop:
	bsf	PORTB, 6
	bcf	PORTB, 7
	call	delay
	bcf	PORTB, 6
	bcf	PORTB, 7
	call	delay
	goto	shortloop


broken:	call	setupled
	bsf	PORTB, 6
	bcf	PORTB, 7
brokenloop:
	nop
	goto	brokenloop


	end