Data risk for RS-485 users?

“Many RS-485 users are completely unaware that they are taking unnecessary risk with their data because of the method they use for driver control,” said Jeff Hunter, design engineer at Sealevel Systems. New driver control methods can help RS-485 eliminate the risks of data contention and corruption, Hunter says.

05/01/2008


“Many RS-485 users are completely unaware that they are taking unnecessary risk with their data because of the method they use for driver control,” said Jeff Hunter, design engineer at Sealevel Systems. New driver control methods can help RS-485 eliminate the risks of data contention and corruption, Hunter says.

The EIA RS-485 specification does not stipulate the method for controlling the driver; therefore, several options have evolved. Some have significant risk of data contention and corruption because of the time required for a device to relinquish control of the network once communication is complete.

Common RS-485 driver control methods are:

  • Application program control (under Microsoft Windows);

  • One-shot (which uses a circuit to activate the enable/deactivate signal);

  • Enable driver when data present (a hardware approach connecting the transmitter data line to the transmitter enable pin);

  • Automatic driver control (in which software automatically recognizes commands to transmit/disable); and

  • Automatic hardware enable (the latest innovation that uses hardware circuitry on the board to control RS-485 communications).

A white paper entitled, “ Eliminate the Risk of RS-485 Data Corruption ,” can be accessed for no charge at www.sealevel.com.