Ray Gardiner wrote:

> <snip>
>
> >
> >where am i going wrong please ?
> >
> >thanks very much for your help
> >i appreciate it
> >glen
>
> Hi Glen,
> I assume that your code does something after the "movwf  strttmr"
> and doesn't just run off into the "table" subroutine. .. :-)

yes ray , "movwf    strttmr" does continue on in the program.

>  the "weak-pullups" enabled in the OPTION register.

yes they are enabled

> And another thing, why have you got the 10k resistor there anyway?
> it is not needed for switches. (assuming the weak-pull-ups are enabled).
>

i have removed the 10k res.& checked the following
vdd=    5v
low=    0v
high=    1.75v


i have tried the different switch settings but still no change !

  " stop press "
i think i've found the problem.
the circuit works when the single strttmr value & no pullups are used.

 i am using rb3 to sense the ac line i/p.& synchronise
(i am testing with 16vac till i get the code to work correctly)
but when i get to using the 240v line voltage the same problem would arise,
can't read zero crossing due to pullups!

when i use pullups the prog won't work , because the ac i/p (rb3) doesn't go
down to read a zero
goes no lower than 1.8v
*****************
with this modification using selectable switch values via lookup table
& since i need pullups to work the two switches.

is their a way to code other than to enable pullups to get the switch values
&
then disable rb3 pullup
so rb3 can sense line & synchronise(able to read zero crossing)

heres the code (lookup table only included in sub routines)

;   vars
PORTA   equ     0x05  ;CPU equates (program memory map)
PORTB   equ     0x06  ;CPU equates (program memory map)
souter equ 0x0c ;
sinner equ 0x0d ;
inners equ 0x0e ;
outers equ 0x0f ;
innerf equ 0x10 ;
outerf equ 0x11 ;
chkcnt equ 0x12 ;
strttmr equ 0x13 ; no of counts
switch equ 0x14 ;
STATUS equ 0x03    ;CPU equates (program memory map)
w       equ     0  ; destination designators
f         equ     1 ; destination designators

;**********************************************************************
;                   porta set-up
        org     0x000             ;address 000 program start
start   movlw 0xff              ;ff hex moved to w register
        tris    PORTA             ;porta set as inputs
;
;**********************************************************************
;                    PORTB set-up
        movlw   0x0f            ;00001111 hex moved to w register
        tris        PORTB         ;PORTB set o/p's 4,5,6,7,inputs 0,1,2,3
;
;**********************************************************************
         clrf  STATUS
; ============= prescaler setup ==============
         movlw     b'01000111' ;scale 1:256 , pullups enabled
         OPTION
; ============= counter setup ==============

 ;code below is used for 2 switches
 ; init strttmr from input pins
             movf       PORTB,w          ;get values of RB0 & RB1
             andlw     0x03             ; extract out bits 0,1 of PORTB
(strttmr value)

 CALL     table                         ; use look up table
             movwf     strttmr     ;move selected value from table to
strttmr

;**********************************************************************
;       ============== program start =============
         movlw     0x00              ;move 00 hex to register w
         movwf     PORTB             ;move register w to PORTB (clear PORTB)

; ============= initialise timer setup ==============

        initmr         movlw .215          ;40 * .000256 = 10 ms
         movwf     TMR0

loop CALL     chcycs    ;check for zero crossing
         CALL     sttimer
         CALL      tog

; ============= check timer ==============
         movf         TMR0,w          ;move f reg to w
         btfsc         STATUS,Z         ;if !0 ,GOTO loop
         GOTO      loop
         decfsz         strttmr,f             ;decrement strttmr by 1
         GOTO         initmr              ;go around for next delay

 ;drop thru to stop

stop     GOTO         stop
;=======================================================================
;                       delay sub-routine
table     addwf         PCL,f
             retlw         d'25'         ; 00 : 250ms (switch position 1)
             retlw         d'50'         ; 01 : 500ms (switch position 2)
             retlw         d'75'         ; 10 : 750ms (switch position 3)
             retlw         d'100'         ; 11 : 1000ms (switch position 4)

thanks for your help ray
it's very kind of you
glen