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THVD4431: Device wiring with UART IC auto RS485 half-duplex direction control

Jan
Prodigy 10 points
Part Number: THVD4431

Tool/software:

Hello,

I am currently building a seriel interface with the THVD4431 multiprotocol transceiver in connection with an PCIe UART IC (XR17V354, MaxLinear (former Exar)).
The UART IC contains a so called 'auto RS485 half-duplex direction control' feature which i would like to integrate in my design.
It is stated that the UART IC uses either the RTS or DTR Pin to activate it. (In my case L4 or L6)

In my understanding, in RS-485 half or full-duplex mode these pins are not relevant.
I saw in old designs that the RTS/DTR Pin is bridged with the DIR Pin of the transceiver.

My Questions are now:
1. Does the connection of RTS/DTR to DIR also apply to the THVD4431 to realize the auto RS-485 feature?
and if so
2. Does this connection affect the RS-232 3T5R mode? (I couldn't find proper information about the DIR Pin state in RS-232 3T5R mode in the data sheet)

Or am I on the complete wrong path?

Thank you in advance for answering.

Regards,

Jan

  • +1
    Guru 282500 points

    When in RS-485 mode, you must route the "driver enable" signal to the DIR pin.
    When in RS-232 mode and you want to use the RTS or DTR signal, you must route that signal to the appropiate L4/L6 pin.

    As fas as I know, the DIR or L4/L6 pins are ignored when in the 'wrong' mode.

  • +1
    TI__Guru 59940 points

    Hi Jan,

    Clemens is correct. To add, as long as the auto RS485 feature uses a logic high on DTR/RTS to enable the RS485 driver and a logic low to put the device in receive mode then it should work.

    -Bobby