;
; ***************************************************************************
; ***  Bubble Software Parallax to PIC Source Converter. Copyright 1999.  ***
; ***  http://www.picnpoke.com                 email: sales@picnpoke.com  ***
; ***************************************************************************
;
; SLEEP period
; Puts the PIC to sleep for 1 to 65535 units of 2.3 seconds.
; The 2.3-second value is approximate. Wide variations in operating temperature
; or supply voltage can double or halve this figure. See the discussion in the
; Nap program listing.

; Device data and reset vector: Note that the watchdog timer is ON.
	P = pic16c55
	#include <16c55.inc>   ; processor assembler definitions
	_CONFIG _xt_osc & _wdt_on & _protect_off
 reset start

 org 8
hiB 	Res	1
lowB 	Res	1

 org 0
             SLEEP                      ; Take twos complement
             COMF lowB                  ; of the 16-bit counter
             BTFSC status,z             ; If zero, lowB overflowed,
             INCF hiB                   ; so carry into hiB.
             MOVLW d'15'                ; Assign prescaler (div 128)
             OPTION                     ; to wdt, then write to option.
             SLEEP                      ; Go to sleep.
; SLEEP (cont)

start        MOVLW d'0'                 ; Make RB all outputs for LEDs.
             TRIS 6h
             CLRW                       ; At the beginning of the program,
             BTFSC status,pd            ; we set up a Branch-type routine
             IORLW d'1'                 ; to take action based on the
             BTFSC status,to            ; power-down (pd) and timeout (to)
             IORLW d'2'                 ; bits.
             ADDWF pcl                  ; | to | pd|
             GOTO count_dn              ; | 0	| 0	| wdt wakeup: count down.
             GOTO watch_fail            ; | 0	| 1	| wdt timeout: handle it.
             GOTO mclr_pin              ; | 1	| 0	| mclr wakeup: handle it.
             GOTO main                  ; | 1	| 1	| power 1st on: goto main.

; This code executes when power is first applied to the PIC (after start).
; It consists of a loop in which the PIC sleeps for 2 hours, then inverts port RB.

main         MOVLW 0x0C                 ; Load 3125 (0C35 hex)
             MOVWF hiB
             MOVLW 0x35                 ; into 16-bit counter.
             MOVWF lowB
             CALL Sleep                 ; Hibernate for 3125 x 2.304 secs.
             MOVLW d'255'               ; Wake up after 2 hours, invert RB.
             XORWF 6h
             GOTO main                  ; Do it again.

; When the PIC wakes up from a wdt timeout, it executes this code, which
; increments the 16-bit value in lowB and hiB, and determines whether it's
; time to wake up. If it's not, the PIC goes back to sleep. If it is, the program
; returns to resume execution at the instruction following call Sleep.

count_dn     INCF lowB                  ; lowB = lowB+1.
             BTFSC status,z             ; Overflow in lowB?
             INCFSZ hiB                 ; Yes: hiB=hiB+1, overflow?.
             SLEEP                      ; No overflow: back to sleep.
             RETLW 0h                   ; Overflow. Return to caller

; In an actual application, this code would contain instructions for dealing
; with a reset pulse waking the PIC out of sleep. Here, we have an empty
; routine that just returns to the main loop.

mclr_pin     RETLW 0h                   

; In an actual application, this code would contain instructions for dealing
; with a watchdog-timer timeout during program execution. Here, we have an
; empty routine that just returns to the main loop.

watch_fail   RETLW 0h