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SN65HVD1473: Using SN65HVD1473 in half duplex

Part Number: SN65HVD1473

Hi team,

I need some clarity on  SN65HVD1473 RS-485 transceiver.

•Can I use the above IC in Half duplex mode by shorting its differential pins (ie; A with Y , B with Z) .

Since my master has 2 wire output(half duplex) and the slave has four wire (full duplex) and I cant alter this.

•If  half duplex is possible then what are necessary things(protection, series termination)  that need to be done in the circuit to work fine? Can I get any reference(application note, schematics) where these kind method is employed?

•How the IC will get to know that whether to transmit or receive , What should be the status of the RE and DE pins?

Please help me out in this.

Regards, 

Karthik

  • Karthik,

    A full-duplex transceiver can operate as a half-duplex transceiver when the differential output lines are tied to the differential input lines. The non-inverting output (Y) should be tied to the non-inverting input (A) and the inverting output (Z) should be tied to the inverting input (B).

    Unfortunately I am unaware of any example schematics or notes that cover full duplex to half duplex conversion. It is recommended that one uses the IC for its inherent duplex. The same protection devices would be used on the bus lines as you would use in a typical half duplex IC such as TVS diodes.

    RE and DE would be enabled/disabled appropriately for transmitting or receiving. Enable DE for transmitting and RE for receiving.

    -Lucas

  • Hi Lucas,

    Thanks for your reply.

     Here in Master SN75176 RS-485 transceiver is used and in slave SN65HVD1473 RS-485 is used , now if i make SN65HVD1473 as half duplex , will I be able to interface with the master (SN75176)?

    Since SN75176 digital input voltage is 5V and SN65HVD1473 is 3.3V will it work fine and communicate between master and slave?

    Since RS-485 is standard protocol this operating voltage might not effect in communication , this is what i believe?

    If there is anything that I must consider please suggest.

    Any electrical parameters that should be checked , Please suggest?

    Regards,

    Karthik

  • Karthik,

    The SN75176 and the SN65HVD1473 transceivers should communicate with each other ok as their voltage input tolerances and logic thresholds are compatible. RS 485 is a physical layer standard and the communication should be ok as long as the communication speeds are less than or equal to 5mbps . 5mbps is the limitation of the SN75176 for RS 485.

    -Lucas