TCA9535: Read from multiple device

Taketo Sato said:

Part Number: TCA9535

Hello team,

I have a question about TCA9535 programming for read operation.

My customer would like to read port0 and port1 data from three TCA9535s like below.

• deviceA port0, port1 --> deviceB port0, port1 --> deviceC port0, port1 --> deviceA port0, port1 --> deviceB port0, port1

 To do this, we have to proceed below sequence.

• device A: Device Address(W) --> Register Address(Port0) --> Device Address(R) --> Data byte(Port0) --> Data byte(Port1)
• device B: Device Address(W) --> Register Address(Port0) --> Device Address(R) --> Data byte(Port0) --> Data byte(Port1)
• device C: Device Address(W) --> Register Address(Port0) --> Device Address(R) --> Data byte(Port0) --> Data byte(Port1)
• device A: Device Address(W) --> Register Address(Port0) --> Device Address(R) --> Data byte(Port?) --> Data byte(Port?)
• device B: Device Address(W) --> Register Address(Port0) --> Device Address(R) --> Data byte(Port?) --> Data byte(Port?)

In this sequence, do we need Device Address(W) --> Register Address(Port0) writes after the second cycle?

[Bobby] No, because you fulfilled the requirement of setting the internal pointer in the first transaction. You can just do the read transaction without the write.

My customer would like to reduce the writes for fast reading, if possible.

Also datasheet says that "After a restart, the value of the register defined by the command byte matches the register being accessed when the restart occurred."

This means that if erase the writes in above example, data order what we read in second cycle will be Port1 then Port0, correct?

[Bobby] Yes.

Best regards,

This looks correct to me.

Thanks,

-Bobby