;
; ***************************************************************************
; ***  Bubble Software Parallax to PIC Source Converter. Copyright 1999.  ***
; ***  http://www.picnpoke.com                 email: sales@picnpoke.com  ***
; ***************************************************************************
;
; NAP period (in w)
; Puts the PIC to sleep for a short period of time.
; The length of the nap may be in the range of 0 to 7 and is passed
; to the subroutine in the w register. The length of nap (in seconds) is
; 2^w * 18 ms, as follows:
;	w = 0: nap = 18 ms
;	w = 1: nap = 36 ms
;	w = 2: nap = 72 ms
;	w = 3: nap = 144 ms
;	w = 4: nap = 288 ms
;	w = 5: nap = 576 ms
;	w = 6: nap = 1152 ms
;	w = 7: nap = 2304 ms
; The 18-ms value is very approximate. It is based on a supply
; voltage of 5 Vdc and an operating temperature of 77 degrees F.
; At higher temperatures and lower supply voltages, it can be much
; longer--even double--the nominal 18 ms. Likewise, at lower
; temperatures and higher supply voltages it can fall to half.
; Note that Nap uses one level of the call/return stack.
	
; 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 0

Nap          IORLW d'8'                 ; Set option.3 to assign prescaler
             OPTION                     ; Lower 3 bits are prescale rate.
             SLEEP                      ; Go to sleep

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 |
             RETLW 0h                   ; | 0	| 0	| wdt wake: return.
             GOTO wdt_fail              ; | 0	| 1	| wdt timeout: handle it.
             GOTO mclr_pin              ; | 1	| 0	| mclr wake: handle it.
             GOTO main                  ; | 1	| 1	| pwr on: main.

; This code executes when power is first applied to the PIC (after start).
; It's a loop in which the PIC takes a 1.152-second nap, then inverts
; port rb. The result is that LEDs connected to RB flash at the rate of the
; nap period.

main         MOVLW d'6'                 ; Set up a 1152-ms nap.
             CALL Nap                   ; Snooze for >1 second.
             MOVLW d'255'               ; Wake up and invert RB.
             XORWF 6h
             GOTO main                  ; Do it again.

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

wdt_fail     RETLW 0h                   
             
             
             end