http://www.piclist.com/postbot.asp?id=piclist\1998\08\10\144809a


I know this is a very old post below but I wanted to say that I ran in to
this exact same behavior on a project when using a 16F877.

While using CCP1 in Capture mode and CCP2 in compare mode, CCP2 would work
correctly when CCP2CON<3:0> is set to 1000b (Compare mode, set output on
match) but when set to 1001b (Compare mode, clear output on match) the
output is cleared immediately on writing the mode to CCP2CON.

This is exactly as described below by Paul.

I think this should probably be listed in an errata, who should I contact?

-Eric



>I'm using the PIC16c73a  to do a PWM on CCP2 and a compare on CCP1.  I'd
>
>like to use the clear on compare mode (with timer1), but when I write
>0x09 to the CCP1CON, the pin(RC2) is cleared on _that_ instruction.
>Actually, on the 3d clock phase relative to when pin writes usually
>occur.  The code works fine in simulation mode.  The problem occurs in
>silicon.
>
>Here's a (stylized) snippet of my code:
>
>     bcf    timer1enable
>     clrf    tmr1L
>     clrf    tmr1H
>
>     movlw    comparevalue
>     movwf    ccpr1L
>     clrf    ccpr1H
>
>     clrf    ccp1con
>     bcf    pir1,ccp1IF
>     movlw    ccp1modecontrolbyte        ; 0x09
>     movwf    ccp1con
>
>I've verified that each of the registers tmr1L, tmr1H,ccp1con,pir1,
>ccpr1L, ccpr1H all contain the correct value after writing to them.  I
>know there is an errata about timer1 registers sometimes inadvertently
>incrementing.  The appropriate pin _is_ set up as an output.
>
>
>If I try the pin SET on compare mode, by writing 0x08 to CCP1CON, the
>compare works perfectly over the whole range of possible compare
>values.  This is with exactly the same code otherwise.  I've also tried
>different initialized pin states, to no avail.
>
>Any suggestions?.  I have the errata for rev B silicon dated 11/96.  Is
>this related to the #2 errata about the CCP special event trigger on
>compare?  Is there a newer errata?  Does anyone have any simple code
>that I can compare my code with?
>
>I've passed this problem on to the Microchip rep in Chicago, but they
>seem to be rather busy although they promised to look at it.
>
>
>Paul

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