> -----Original Message-----
> From: Barry King [SMTP:barry@NRGSYSTEMS.COM]
> Sent: Thursday, January 04, 2001 3:01 PM
> To:   PICLIST@MITVMA.MIT.EDU
> Subject:      Re: [EE]: I2C Question
>
> To be robust, one must handle the cases where the master is reading
> more bytes then the slave transmitter is expecting to supply.  Most
> notably, if your PIC SSP module is doing a slave transmit, it WILL
> LOCK SCL low while waiting for the next byte to be loaded into the
> SSP.  Firmware MUST supply another byte if the master asks (by ACKing
> the previous byte), even if the byte count is "wrong".  I got bit by
> this when I had bus errors. The slave thought he sent all his bytes
> then went back to doing something else and left the SSP holding SCL
> low, locking up the bus.  The only way to get the SSP out of slave
> transmit mode (short of resetting the SSP) is to have the master NACK
> that last byte.
>
This is exactly why I asked the question.  I knew of this problem and had
coded my master software accordingly to send a NACK after the last byte.
However, after re-reading the Philips guide I wasn't sure if this was
correct, so I tried not sending anything after the last byte which also
worked fine.  Due to popular opinion I've switched back to sending the NACK
:o)

Regards

Mike

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