Role of Enable pin in EIA/TIA 485

Hi all, EIA/TIA 485 is an Hardware Specification, it supports both two wir and four wire mode of operation. I came across these points, "Balance line driver can have

1).Two output terminals termed as A & B where the data is transmitted. 2).A signal ground connection. 3).An input signal called an "Enable" signal. The purpose of the Enable signal is to connect the driver to its outpu terminals, A & B."

As far as I have understood, in two wire mode of EIA/TIA 485 the enabl signal is "NOT" on the reciever of the device, so only either transmitte or receiver is active at the same time(In case of half duplex). While if want to implement EIA/TIA 485 in four wire mode(full duplex),how do connect my signal pin? What is the role of the Enable signal, when it com to the two wire or four wire mode?

Please do correct me if i have misunderstood the concept. This message was sent using the comp.arch.embedded web interface o

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Reply to
Swizi
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I think your questions were somewhat answered earlier. Please keep things in that thread. If you disregard everyone, everyone will disregard you.

Reply to
Bryan Hackney

If you do not disable the receiver during transmission, the transmitted data will be echoed on the RxData pin and you usually would have to remove this echo in software before starting to read the response from the other node.

You need a transceiver chip with at least 10 pins, the A/B and A'/B' RS-485 signals, the TTL RxData and TxData signals, the transmitter and receiver enables and Vcc and Gnd.

Paul

Reply to
Paul Keinanen

Or you could use a pair of RS-485 transceivers, one with Tx enabled, one with Rx enabled.

Steve

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Reply to
Steve at fivetrees

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