>-----Original Message-----
>From: Jinx [mailto:joecolquitt@CLEAR.NET.NZ]
>Sent: 25 June 2004 14:02
>To: PICLIST@MITVMA.MIT.EDU
>Subject: Re: [PIC:] MSSP module
>
>
>> >         bcf     pir1,sspif
>> >         mov     0x55,sspbuf   ;send data
>> >         btfsc   pir1,sspstat,r_w
>> >         bra     $-2
>
>> I'm a little surprised that this works
>
>And you'd be right. I did spot that it was not the same as
>the original .asm. pir1,sspif is what it should be
>
>I tried it just out of interest, and btfsc pir1,sspstat,r_w
>actually compiles to btfsc  pir1,pspif. Which doesn't work
>
>Anyway, apart from that little hiccup, look OK ?

You know, I hadn't even spotted that there were three operands!  The point I
was really trying to make was about the next section of code that waits for
sspif to be set: (my comments)

bcf     pir1,sspif      ; clear interrupt flag
mov     0x55,sspbuf     ; load SSPBUF with data to be sent
btfsc   pir1,sspif      ; wait for data to be sent
bra     $-2                     ; data not sent, keep checking

At this point the PIC has clocked the ACK bit in, RW will be clear and SSPIF
will be set

bcf     pir1,sspif      ; clear interrupt flag
btfss   pir1,sspif      ; is interrupt flag set?
bra     $-2                     ; not yet, keep trying

The last three instructions would seem (to me) to cause an endless loop.
The PIC has set the interrupt flag when the data has been clocked out and
the ACK bit clocked in.  You then clear the interrupt flag and wait for it
to be set again, but with nothing in SSPBUF that interrupt is not going to
happen.  I may be missing something...

Regards

Mike




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