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TCA6424A: Register read back procedure

Takashi Onawa
Genius 13200 points
Part Number: TCA6424A

Hi Team,

I have two simple question about a read back procedure of TCA6424A on I2C bus.

1. Is it acceptable to use “STOP and START condition” instead of “Repeated START condition”?
2. Is it necessary to leave high on SDA by Master as NACK at the end byte of read?

My customer expect to use "STOP and START condition" and ACK also.

Regards,

Takashi Onawa

  • 0
    TI__Genius 17225 points
    Hello Takashi,
    Let me double check this before I reply.
    -Francis Houde
  • 0 in reply to fhoude
    TI__Genius 13200 points
    Hi Francis,

    How's it going?
    My customer is waiting our comments to fix their software.

    Regards,
    Takashi Onawa
  • 0
    TI__Genius 17225 points

    Hello Takashi-san,

    Here are your answers:

    1)  Yes, it acceptable that you do a "STOP and START" condition instead of the "repeated START", but keep in mind if you are doing multimaster you are letting the bus go and the other master could take over the bus after that STOP condition.  Most applications aren't Multi-Master so that isn't a problem.

    2)  Yes, you must leave the SDA by master high, NACK< at the end of the read byte.  This sets up the stop condition.  If you pull low, it will look like a ACK and the SLAVE could take over the bus while not allowing the master to do the STOP condition, which could leave the bus stuck.

    -Francis Houde

  • 0 in reply to fhoude
    TI__Genius 13200 points
    Hi Francis-san,

    Thanks for the clear answers. I understood "STOP and START condition" is acceptable and NAK is necessary at the end of read packet for TCA6424A.

    Regards,
    Takashi Onawa