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THVD1450: THVD1450: Rx abnormal working

Steven He92
Expert 2125 points
Part Number: THVD1450

Dear Sir,

My customer use THVD1450 to do a two port communication test. have a issue as below picture

Port-1 sent data to Port-2, as you see Rx is Hi to Low during Tx action.

I check THVD1450 table-2: /RE=H  Rx signal is Z(high impedance) but see Fig-1 show Rx pull-low.

Please you kindly review & provide suggestion.

Thanks!

Steven

  • 0
    TI__Mastermind 25705 points
    Steven,

    Yes, as RTS becomes low, RX is disabled and RO is high impedance. Can you check the load condition of RO pin to see if there is any pull down to make the voltage low?

    Regards,
    Hao
  • 0 in reply to Hao L
    Prodigy 50 points
    Hi Hao,

    We disconnect TX/RX from SIO and PU on RX, just turn the RTS transition for DE/RE. We still see the abnormal RX waveform.

    James Wang
  • 0 in reply to James Wang41
    TI__Mastermind 25705 points
    James,

    We can check if RO is high impedance by the following DC tests: 1) put a large pull up resistor (10kOhm) on RO, to see if RO is close to Vcc when REB is high; 2) put a large pull down resistor (10kOhm) on RO, to see if RO is close to GND when REB is high. You can also change the value of the resistor to get a ball park of the impedance level of RO. Please let me know if it makes sense to you.

    Regards,
    Hao