; program writes SOS msg into flash then turns LED green
; when serial interrupt received, turns off interrupts, turns off
; power, transmits contents of SSPCON1 by flashing LED red, repeats
; (next version will transmit SOS code first, then contents of 
; SSPCON1)


; to start, need to write into flash, starting at 30 0000h:
; 10 10 10 00 | 1110 1110 | 1110 00 10 | 10 10

	include common.inc

	extern	led_green
	extern	led_red
	extern	led_black

	extern	informative_panic


;---------------------------------------------------------------------------
; reserved access bank locations

WREG2		equ	00h	; a 2nd working reg :-)
WREG3		equ	01h	; a 3rd working reg :-)
WREG4		equ	02h	; a 4th working reg :-)
BLANK		equ	03h	; register full of zeros
TESTFLASH	equ	04h	; test LED flash pattern



;---------------------------------------------------------------------------
; memory location definitions

ERROR_BUF_PAGE	equ	3	; error codes on flash p3
F_ERROR_U	equ	30h	; upper part of error memory locations
F_SOS_H		equ	00h	; high (middle) part of SOS error memory loc.
F_SOS_L		equ	00h	; lower part of SOS error memory loc.


;---------------------------------------------------------------------------
; error messages

err_SOS	equ	0	; msg 0 = SOS

;****************************************************************************

;----------------------------------------
readout
; Flashes the per-pic led red and black in a specified pattern.
; The pattern is specified as the state for 8 identically-long time
; periods each as long as a morse `dot', encoded into a byte with
; most significant bit first.
; 		On entry		On exit
; W		any			undefined
; WREG2		flash pattern		preserved
; WREG4		any			undefined
;
	clrf	WREG4,0		; clear loop counter (WREG4)
	rrncf	WREG2,1

readout_loop
	movlw	8
	cpfslt	WREG4,0		; if loop counter >=8, return
	return

	rlncf	WREG2,1		; top bit goes into N flag, ie Negative if 1
	bn	readout_if_led_on
readout_if_led_off
        call	led_black
	bra	readout_endif_led

readout_if_led_on
	call	led_red
readout_endif_led
	incf	WREG4,1,0	; increment loop counter
	call	waiting
	bra	readout_loop

;****************************************************************************

        code

;****************************************************************************
; this is what happens when we panic

informative_panic
; switch off interrupts and power
; reconfigure timer0 for writing diagnostic msg to the LED

        clrf    INTCON,0        ; disable all interrupts EVER
        bcf     PORTC,1,0       ; switch off booster

	movlw	10101100b
	movwf	TESTFLASH


; re-initialise timer0 config
        bcf     T0CON,6,0       ; p107 Timer0 -> 16bit mode
        bcf     T0CON,5,0       ; timer0 use internal clock
        bcf     T0CON,3,0       ; use prescaler
        bsf     T0CON,2,0       ; }
        bcf     T0CON,1,0       ; } prescale value 1:32 (13ms x 32)
        bcf     T0CON,0,0       ; }

	clrf	BLANK,0
panic_loop
;	errmsg	err_SOS,0	; transmit SOS in red
	movff	TESTFLASH,WREG2
	rcall	readout
;	readout	BLANK,0		; transmit blank buffer
	call	led_green
	call	waiting
        goto    panic_loop

;****************************************************************************
; GENERAL SUBROUTINES

;----------------------------------------
waiting
; waits for a fixed interval, depending on the configuration of TMR0

        bcf     INTCON,2,0      ; clear timer0 interrupt bit (p109)
        clrf    TMR0H,0         ; p107 set high byte of timer0 to 0 (buffered,
                                ; only actually set when write to tmr0l occurs)
        clrf    TMR0L,0         ; set timer0 low byte - timer now set to 0000h
loop
        btfss   INTCON,2,0      ; check whether timer0 interrupt has been set -
                                ; skip next instruction if so
        bra     loop
        return


;****************************************************************************

	end