RS485 Half-Duplex Operation

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strahd_von_zarovich

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Hi, i have a device which i should communicate with, via RS485 bus. I am going to use ADM2682E as a driver and receiver. My question is

- Is it ok to connect DE and /RE pins each other and control them with one external logic since i use half-duplex operation ? So when i want to send data, making the logic high , DE is high enabling the drivers, and /RE is low disabling the receivers ?

Regards.
 

Hi,

Yes. You could connect them.

But you can leave the reciever continouly active.
In the block diagram it shows just to switch the RxD line high-Z.

If you switch the receiver inactive, you should consider to use a pullup resistor at the RxD line to prevent it from floating.
If you want to transmit data, there is no need to switch the receiver inactive. Both can be active at the same time.

When the reciever is active during transmitting, then you will receive the sent out data as a local feedback.

Klaus
 

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