DT CMP Interrupt Problem

[Pic2008]

I'm using PIC16F877, and have 2 analog inputs IN1 and IN2. I want to generate interrupt if voltage IN1 > IN2. Do I keep reading the AD register and compare it with IN2 voltage during each CMP interrupt? Or is there a more efficient way to implement this?

define OSC 20
INCLUDE "DT_INTS-14.bas"     ' Base Interrupt System
INCLUDE "ReEnterPBP.bas"     ' Include if using PBP interrupts

ASM
INT_LIST  macro    ; IntSource,  Label,  Type, ResetFlag?
       INT_Handler    CMP_INT,  _Int_Cmp,   PBP,  yes        
    endm
    INT_CREATE               ; Creates the interrupt processor
ENDASM

@    INT_DISABLE   CMP_INT     ;Comparator int

ADCON1= %00000000      'enable all analog inputs
LED var PORTB.7

loop:
'start ad here

'end ad 
pause 50
goto loop

'---[CMP - interrupt handler]----------------------------------------------
Int_Cmp:
toggle LED 

'read and store ad result here

@ INT_RETURN

I haven't finish the code above, but am getting a compilation error in Microcode "symbol not previously defined [CMIF]". PLease help.

[Darrel Taylor]

The 16F877 doesn't have a Comparator module.

The 16F877A does.
<br>

[Pic2008]

I don't have 16F877A now. If I continue to use 16F877, what is the best method to detect IN1>IN2?

This means I don't have any interrupt, and I have to poll the go/done bit in ADCON0 while sacrificing on executing other task?

[Darrel Taylor]

The A/D module has an interrupt that fires when a conversion is complete.

You don't have to sit in a loop polling the Go/Done bit.
<br>

[Pic2008]

Oh, that's great. How do I implement this using DT interrupt?
Below is what I'm currently doing, using pause 25ms before the next AD.

define OSC 20      

' Define ADCIN parameters
Define  ADC_BITS        10     	' Set number of bits in result
Define  ADC_CLOCK       3     	' Set clock source (3=rc)
Define  ADC_SAMPLEUS    50    	' Set sampling time in uS


ADCON1= %00000111      'PIC16F877 all analog input except RE1,RE2

 'start AD here 
        ADCIN 0, adval				' Read channel0 RA.0 to adval
        pause 25
        ADCIN 1, adval2				' Read channel1 RA.1 to adval
        pause 25