Seeking distance or speed on an RS-485 bus?

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Seeking distance or speed on an RS-485 bus? [Copy link]

Network designers know that the RS-485 standard has a proven track record of robust and reliable communications, making it the recommended standard for multi-point differential data transmission in industrial networks. While the RS-485 standard has stood the test of time, as other elements of the system or network change, RS-485 transceivers continue to evolve and change to meet those needs. Modern networks are often a combination of control systems and data links, and the requirements change as the application changes.

As network requirements increase, many equipment manufacturers are demanding that control channels not only span greater distances in the network, but also send high-speed data over the network. The RS-485 bus standard supports data transmission distances up to 4000 feet (1200 meters), but the maximum data rate cannot be achieved at the maximum cable length: the longer the cable, the slower the data rate.

For applications that require synchronous (parallel transceiver) signal timing, that’s where selectable data rate can step in to save the day. You no longer have to choose between cable length and data rate. By qualifying the SN65HVD01 selectable data rate transceiver once, designers can find the common ground between distance and speed. Programmable logic controller (PLC) designers can use the SN65HVD01 transceiver to send control information at rates up to 250kbps to remote IO modules within the factory up to 1200 meters from the PLC. Some industrial networks may require more data to move between nodes in the network. The same device can support higher data rates up to 20Mbps by using the slew rate select feature.

Furthermore, reducing the power consumption of these networks is becoming increasingly important. Very low standby currents that can interface to 3.3V or 1.8V FPGAs or microprocessors not only help achieve lower system power consumption, but also reduce the need for costly level shifters.

Upgrading is easy, too. Modern transceivers are not only designed to be backwards compatible with base RS-485 transceivers, but they also offer greater flexibility and robustness. The SN65HVD01 is one of many devices in a family of RS-485 transceivers that supports IEC ESD protection—now with uncompromising flexibility! If this transceiver were the car on the RS-485 bus, think of it as a fast sports car with hybrid power and the protection of a tank that will go the distance you need it to.