please dont rip this site

Piclist Cheapic EGGTIM4M

 
;----------------------------------------------------------------------;
; EGGTIM4M.ASM   A 3 minute countdown timer for boiling eggs, 4 MHz osc;
; Pushbutton on RB4 starts countdown.  Displays minutes and tens of    ;
; seconds in binary on LEDs.  Zero represented by all leds lit.        ;
; A second pushbutton can be added to cycle through starting times.    ;
;----------------------------------------------------------------------;

;                            .-----------.
;                           -|RA2     RA1|-       V+ = 4.5 or 5 Volts
;                           -|RA3     RA0|-       X = 4 MHz cer. res.
;                           -|RA4    OSC1|--|X|___ gnd
;   -{r}- = 470 ohm    V+ ---|MCLR   OSC2|--|X|  
;   -|<- = LED        gnd ---|Vss     Vdd|--- V+
;            gnd ---|<--{r}--|RB0     RB7|-         
;            gnd ---|<--{r}--|RB1     RB6|-         
;            gnd ---|<--{r}--|RB2     RB5|---[PB]--- gnd       
;            gnd ---|<--{r}--|RB3     RB4|---[PB]--- gnd        
;                            '-----------'         
;                               PIC16F84      -[PB]- pushbutton


        LIST P=16F84           ;  tells which processor is used
        INCLUDE "p16f84.inc"   ;  defines various registers etc. Look
        ERRORLEVEL -224        ;  supress annoying message from tris
        __CONFIG _PWRTE_ON & _XT_OSC & _WDT_OFF   ;  config. switches

         #DEFINE button1 PORTB, 4   ; RB4 pushbutton to ground
         #DEFINE button2 PORTB, 5   ; RB5 pushbutton to ground

;----------------------------------------------------------------------;
;            Here we set up the user defined registers                 ;
;----------------------------------------------------------------------;
           CBLOCK H'0C'         ;  first free register address is 12
               sec              ;  keeps track of seconds
               sec10            ;  keeps track of tens of seconds
               mins             ;  keeps track of minutes
               cntmsec          ;  counter used in millisecond delays
               counter          ;  general counter
           ENDC

           ORG 0              ;  start a program memory location zero

           goto main          ;  jump over the interrupt routine

;----------------------------------------------------------------------;
;           initialize the ports, set up interrupts etc:               ;
;----------------------------------------------------------------------;
init:
         movlw B'00000000'    ;  all outputs
         tris PORTA           ;  on PORT A  
         movlw B'00110000'    ;  RB4 & RB5 inputs, all others outputs
         tris PORTB           ;  on PORT B
         movlw B'00000000'    ;  port B pull-ups active
         option
         clrf sec             ;  sec = 0
         clrf sec10           ;  sec10 = 0 
         movlw D'3'           ;  and minutes = 3
         movwf mins   
         movlw D'10'          ;  initialize counter to 10
         movwf counter        
         return

;----------------------------------------------------------------------;
;          Wait for pushbutton. Start countdown when pressed.          ;
;----------------------------------------------------------------------;
waitpushbutton:
         movf mins, W         ;  display minutes on LEDs at start 
         movwf PORTB

  ; to add a pushbutton on RB5 to select starting minutes uncomment the
  ; next two instructions
  ;       btfss button2        ;  button2 pressed? skip if not
  ;       call selectstart     ;  select starting number of mins 1-16

         btfsc button1        ;  switch closed, (gives 0)?
         goto waitpushbutton  ;  not yet
                              ;  switch has been detected closed
                              ;  ( no debounce necessary )
         clrf PORTB           ;  lights out
         return

;----------------------------------------------------------------------;
;              Select the starting number of minutes 1-15              ;
;----------------------------------------------------------------------;
selectstart:
         incf mins, W         ;  increment minutes
         andlw H'0F'          ;  limit to 15
         movwf mins           ;  store in mins
waitup:
         movlw 10             ;  delay for 10 msec (debounce press)
         call nmsec
         btfss button2        ;  button 2 up yet?
         goto waitup          ;  no, keep checking
         return

;----------------------------------------------------------------------;
;                    This is the main program                          ;
;----------------------------------------------------------------------;
main:
         call init            ;  set up ports, initialize registers
         call waitpushbutton  ;  wait for button to be pressed 

loop:  
         decfsz counter, f    ;  show time every tenth time
         goto $ +2            ;  skip over next instruction
         goto showtime        ;  display time, (lasts 1 sec)
         call onesecond       ;  delay for one second
nextsec:
         decf sec, f          ;  down one sec
         movlw H'FF'          ;  check for underflow
         subwf sec, W         ;  will give zero if underflow
         btfss STATUS, Z      ;  skip if underflow
         goto loop            ;  else continue
         movlw D'9'           ;  sec to 9
         movwf sec
         decf sec10, f        ;  same for sec10 register   
         movlw H'FF'          ;  check for underflow
         subwf sec10, W       ;  gives zero if underflow
         btfss STATUS, Z      ;  skip if underflow
         goto loop            ;  else continue
         movlw D'5'           ;  sec10 to 5
         movwf sec10
         decf mins, f         ;  now minutes
         movlw H'FF'          ;  check for underflow
         subwf mins, W        ;  gives zero if underflow
         btfss STATUS, Z      ;  skip if underflow
         goto loop            ;  else continue
                              ;  come here when the countdown is over    
finished:
         movlw H'0F'          ;  turn on all leds indicating finish
         movwf PORTB
         movlw D'40'          ;  wait for 10 seconds
         movwf counter        
         call msec250         ;  1/4 sec delay
         decfsz counter, f    ;  finished?
         goto $ -2            ;  not yet
         goto main            ;  start all over again

showtime:                     ;  this lasts approximately one second
     ; usec instructions are insignificant compared to 100's of msec         
         movf mins, W         ;  display minutes
         btfsc STATUS, Z      ;  skip if not zero
         movlw H'0F'          ;  else all LEDs on
         movwf PORTB          ;  turn on LEDs
         call msec250         ;  on for 400 msec
         movlw D'150'     
         call nmsec
         clrf PORTB           ;  blank briefly
         movlw D'200'
         call nmsec
         movf sec10, W        ;  now the same with sec10
         btfsc STATUS, Z      ;  skip if not zero
         movlw H'0F'          ;  else all LEDs on
         movwf PORTB          ;  show 10's of seconds
         call msec250         ;  on for 400 msec
         movlw D'150'  
         call nmsec   
         clrf PORTB           ;  blank
         movlw D'10'          ;  reset counter to 10
         movwf counter
         goto nextsec 

;----------------------------------------------------------------------;
;                        time delay routines                           ;
;----------------------------------------------------------------------;
micro4      addlw H'FF'                ;  subtract 1 from 'W'
            btfss STATUS,Z             ;  skip when you reach zero
            goto micro4                ;  more loops
            return                     

                ;*** N millisecond delay routine ***
msec250:    movlw D'250'               ;  250 millisecond delay
nmsec:      movwf cntmsec              ;  delay for N (in W) millisec
msecloop:   movlw D'248'               ;  1 usec for load
            call micro4                ;  this instruction is 995 usec
            nop                        ;  1 usec 
            decfsz cntmsec,f           ;  1 usec, (2 if skip taken)
            goto msecloop              ;  2 usec, loop = 995+5 = 1 msec
            return 
                    
onesecond:  call msec250               ; delay for one second
            call msec250
            call msec250
            call msec250
            return

         end                           ; end of program

;  Note:   This program differs from eggtimer.asm (used a 32 kHz xtal).
;  That program has errors due to subtile interaction of the isr and main
;  program.  The easiest fix is to not use a interrupt subroutine.




<P>

</BODY></HTML>

file: /Techref/piclist/cheapic/eggtim4m.asm, 9KB, , updated: 2006/1/20 19:31, local time: 2017/11/22 08:12,
TOP NEW HELP FIND: 
54.225.16.10:LOG IN

 ©2017 These pages are served without commercial sponsorship. (No popup ads, etc...).Bandwidth abuse increases hosting cost forcing sponsorship or shutdown. This server aggressively defends against automated copying for any reason including offline viewing, duplication, etc... Please respect this requirement and DO NOT RIP THIS SITE. Questions?
Please DO link to this page! Digg it! / MAKE! / 

<A HREF="http://techref.massmind.org/techref/piclist/cheapic/eggtim4m.asm"> piclist cheapic eggtim4m</A>

Did you find what you needed?

 

Welcome to massmind.org!

 

Welcome to techref.massmind.org!

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

  .