On Tue, Sep 15, 2020 at 2:47 PM Rayagonda Kokatanur <rayagonda.kokatanur@xxxxxxxxxxxx> wrote: > > Hello All, > > I have the following questions wrt SMBUS PEC support on the SLAVE side, > > As we know when Master sends a read request, Slave keeps on > transferring data until STOP/NACK is received from Master. > This means Slave doesn't have a prior idea about how many bytes to > transmit to Master. > > Let's say, the Master wants to read 1 byte of data with PEC enabled, > in this case Slave needs to send a total of two bytes (1st byte data > and 2nd byte PEC). > When Master puts this request on Bus, following events will happens, > > 1. Slave sends 1st bytes > 2. Master receives 1st byte and sends ACK > 3. Since no STOP is received from Master, slave send 2nd byte (But > Master is expecting PEC bytes as 2nd byte) > 4. Master receives 2nd byte and sends NACK/STOP. > > This means Slave didn't send PEC byte and is no longer driving the SDA > line to send PEC bytes. > When Master checks PEC it will not match and Master read will fail. > > How do we handle this case, what is the expected behavior from Slave > as per SMBUS protocol ? > In this case when should Slave send PEC bytes ? > > Please let me know. Please let me know if anyone knows the solution for the above problem. Or any other forum to ask this question. Thanks, Rayagonda > > Best regards, > Rayagonda
