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ISOW1432: full-duplex

Jeff YANG
Mastermind 9385 points

Part Number: ISOW1432
Other Parts Discussed in Thread: ISOW3086

Hi,

We currently have a requirement for full-duplex RS485. Since this chip has two pairs of Tx and Rx, would it be feasible to use it? Thank you. 

485.png

  • 0
    TI__Genius 17770 points

    Hi Jeff,

    Thanks for reaching out.

    Yes, the ISOW1432 is a full-duplex capable device. This is mentioned in the product page as well as datasheet as well.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Mastermind 9385 points

    Hi Varun,

    I have a question regarding the implementation of full-duplex RS485.

    For our source UART signal, aside from the TX and RX pins, do we also need to connect the RTS and CTS pins? Thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Genius 17770 points

    Hi Jeff,

    If a full-duplex communication is required - then DE (Driver Enable) and RE/ (Receiver Enable) both needs to enable during the communication.

    RTS and CTS can be used as RE/ and DE respectively if needed by customer but a simple LOGIC HIGH on DE and LOW on RE/ will also work fine for full duplex.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Mastermind 9385 points

    Hi Varun,

    What are the functional differences between using RTS/CTS to perform RE/DE operations and directly pulling DE high/RE low?

    Thanks!

    Jeff

  • 0 in reply to Jeff YANG
    TI__Genius 17770 points

    Hi Jeff,

    I cannot comment much on the RTS/CTS - you need to verify this from the UART protocol. However, if the RTS/CTS signal are digital signals you can connect them to RE/DE directly but need to make sure that they are always Low/High respectively.

    But asl long as you need Full-Duplex make sure DE is pulled HIGH and RE is pulled low - this is the simplest way to implement 

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Mastermind 9385 points

    Hi Varun,

    Could you please confirm whether this can be implemented in the hardware design? Thanks.

    　①RS485, full-duplex

    　②RS422, full-duplex

    　③RS485, half-duplex

    Jeff

  • 0 in reply to Jeff YANG
    TI__Genius 17770 points

    Hi Jeff,

    If DE and RE are shorted together - then only either Driver or Receiver will be enables at a time and it is suited for half duplex operation only.

    Also, Full Duplex and Half Duplex Operation cannot be achieved using same schematic connection because A/B needs to be shorted to Z/Y on Bus Side to achieve Half Duplex in a Full Duplex capable device - (+) [FAQ] ISO1452: [FAQ] How to configure a RS485 Full-duplex transceiver as Half-duplex? - Isolation forum - Isolation - TI E2E support forums

    You have mentioned that only Full-Duplex is required - for that DE and RE needs to be always set to HIGH and LOW respectively.

    Regards
    Varun

  • 0 in reply to Varun Kumar
    Mastermind 9385 points

    Hi Varun,

    May I ask if RE is inverted internally inside the IC? Logically, with my current use of RTS, I should be able to achieve DE/RE High/Low at the same time.

    The end customer's requirements are RS485 full-duplex, RS485 half-duplex, and RS422.

    The URL you provided should be a design for changing RS485 full-duplex to half-duplex, correct?

    Could you please help to re-verify this? Thank you.

    Jeff

  • +1 in reply to Jeff YANG
    TI__Guru 57525 points

    Hi Jeff,

    Please note that RS-485 interface is protocol agnostic. ISOW1432 simply transfers the data that is applied to it provided the driver is enabled by asserting DE pin. Similarly, the receiver receives data when it is enabled by asserting RE\. It is upto customer when or how to enable the driver and receiver.

    I am not familiar with CTS and RTS pins of XR21V1410 and how they change. Therefore, I will let customer decide how to use them and if they should be connected to DE or RE\. As Varun already explained, DE needs to be HIGH to enable the driver and RE\ needs to be LOW to enable receive.

    I would also like to mention that ISOW3086 is the next generation device to ISOW1432 that offers better overall performance and we recommend that you use this part for your designs to get the best performance.

    Let us know if you have any other questions, thanks.


    Regards,
    Koteshwar Rao