Role of Enable pin in EIA/TIA 485

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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.  
        
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Re: Role of Enable pin in EIA/TIA 485
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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.

Re: Role of Enable pin in EIA/TIA 485

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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.

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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
 

Re: Role of Enable pin in EIA/TIA 485
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Or you could use a pair of RS-485 transceivers, one with Tx enabled, one
with Rx enabled.

Steve
http://www.fivetrees.com



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