Variable changing mid-code in 16F883?

[richard]

for tempvar=0 to 105
address=tempvar<<3

that looked wrong at first if address started a 1600 but it doesn't.
perhaps address gets corrupted every time readout is run,
spaghetti code like that is hard to unravel

[HenrikOlsson]

I'm not saying this is related to your problem but here:

hold1:
  tempbyt=TMR1H
  if tempbyt<>128 then hold1

This will "hold" until TMR1H is 128 and then countinue.
But for how long is TMR1H 128? Are you sure it's not (still) 128 the next time you check?

I would rewrite this.
* For pacing the loop, poll the TMR1 interrupt flag.
* Create a short subroutine for each "task". MeasureA, MeasureB, MeasureC, WriteEEPROM and so on.
* Have a LoopCount variable that counts from 0 to whatever.
* Use a Select Case block to execute whatever tasks are needed at each increment of the loop.

Crude example:

TMR1IF VAR PIR1.0
LoopCount VAR BYTE

TMR1IF = 0
T1CON = %00110001 ' Prescaler = 1:8,  Timer ON

Main:
  IF TMR1IF=0 THEN Main    ' Wait for TMR1 roll over

  TMR1IF=0		   ' Reset interrupt flag.

  Select Case LoopCount
    Case 0
      GOSUB MeasureA
      GOSUB MeasureB

    Case 1
     GOSUB MeasureA
     GOSUB MeasureC

    Case 2
      GOSUB MeasureA
      GOSUB MeasureB
      GOSUB MeasureC

    Case 3
      GOSUB MeasureB
      GOSUB MeasureC
      GOSUB WriteEEPROM
  END SELECT

  LoopCount = LoopCount + 1
  IF LoopCount = 4 THEN LoopCount = 0

Goto Main


MeasureA:
  ' Do stuff
RETURN

MeasureB:
  ' Do Stuff
RETURN

MeasureC:
  ' Do Stuff
RETURN

WriteEEPROM:
  ' Do Stuff
RETURN

[richard]

i had a slightly different take but am amazed at the similarity

#CONFIG
    __config _CONFIG1, _HS_OSC & _WDT_OFF & _MCLRE_OFF & _LVP_OFF & _CP_OFF
    __CONFIG _CONFIG2, _WRT_OFF & _BOR21V
#ENDCONFIG


DEFINE INTHAND   ticker  






ANSEL=0      'all analogue ports to digital
ANSELH=0     'all analogue ports to digital




TRISA=%00101011      '(0=output, 1=input)
TRISB=%00100001      '(0=output, 1=input)
TRISC=%00000000      '(0=output, 1=input) 
TRISE=%00001000      '(0=output, 1=input) 


OPTION_REG=%11000101
PIN_OUT       var PORTC.3  'serial out pin
LED           var portA.2
wsave         var byte    $70 SYSTEM
ssave         var byte    SYSTEM
psave         var byte    SYSTEM
taskflag      var byte
taskswitch    var byte
ro_counter    var byte
ibit          var byte
address       var word
icount        var word


define OSC 20


intcon =$c0
pir1.0=0
pie1.0=1


serout2 PIN_OUT,32,["THERMAL START",13,10] '19200bps
T1CON=$31




main:
    if taskflag then
          taskflag = 0
          taskswitch = taskswitch + 1
          if taskswitch == 4 then  taskswitch = 0
          select case taskswitch 
              CASE 0
                gosub task0
                serout2 PIN_OUT,32,["A",dec ibit,"-",dec icount,"-",dec address,13,10] 
                serout2 PIN_OUT,32,["B",dec ibit,"-",dec icount,"-",dec address,13,10]  
              case  1
                gosub task1
                icount=icount+1
                serout2 PIN_OUT,32,["C",dec ibit,"-",dec icount,"-",dec address,13,10] 
                address=address+16
                serout2 PIN_OUT,32,["D",dec ibit,"-",dec icount,"-",dec address,13,10] 
              case  2 
                gosub task2
                ro_counter =ro_counter +1
                if ro_counter == 16 then
                    serout2 PIN_OUT,32,["READOUT",13,10] 
                    ro_counter =0
                endif
              case  3
                gosub task3 
                
          end select    
    endif
goto main


task0:
'do voltage stuff
return


task1:
'do current stuff
return


task2:
'do other stuff
return


task3:
     LED = ! led 
return




END


asm    
ticker      ;tmr1 isr
    banksel  _taskflag
    bsf _taskflag,0
    banksel PIR1
    bcf PIR1,0
    movf psave,W ; restore PCLATH
    movwf PCLATH
    swapf ssave,W ; restore STATUS
    movwf STATUS
    swapf wsave,F ; restore W (swap avoids changing STATUS)
    swapf wsave,W 
    RETFIE    
endasm