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THVD2452V-EP: THVD2452V-EP

maheswari V
Prodigy 75 points
Part Number: THVD2452V-EP

Tool/software:

Hi team,

In the RS485 how 32 nodes can be connected in the bus

is there any possibility of slave to slave communication in rs485.

How the master communicates with the multiple slaves

  • 0
    Guru 316640 points

    RS-485 is an electrical specification and does not have a concept of masters and slaves; electrically, all nodes behave the same.

    Use MODBUS, or create your own protocol (designate one node as the master, and let it tell each device in turn that it is now allwed to send; or just use collision detection with random backoff).

  • +1 in reply to Clemens Ladisch
    Prodigy 75 points

    Thanks for the reply,

    Can you explain why we can connect the 32 nodes on rs485.

  • 0 in reply to maheswari V
    Guru 316640 points

    On a half-duplex bus, only one node at a time is allowed to transmit data. But all nodes are receiving (and must check whether the data is actually meant for them).

  • 0 in reply to maheswari V
    TI__Guru 72521 points

    Clemens is correct. Just to add, the RS485 standard was designed to allow up to 32 unit loads to exist on the line but modern day RS485 transceivers have a lower unit load than 1 per device. Usually they are around 1/8th unit loads. So if all the RS485 transceivers are 1/8th a unit load, then the total amount of devices allowed on the bus is actually more than 32, it can be a max of 256 (32 x 8 = 256).

    -Bobby