On an SA bus, the minimum requirement is that EOL termination must be enabled on at least one device. Since an SA bus supervisor always has EOL termination enabled, this requirement is always met; however, for enhanced bus performance, we recommend that you enable EOL termination on the devices at each end of the SA bus. See Figure 1 for SA bus EOL termination scenarios. In this example the configuration that is labelled Best is preferred because the wire is terminated at both ends. The other configuration labelled Acceptable has only one termination, and therefore is more prone to communication errors depending on the amount of loads, wire length, and noise conditions. Avoid using the last configuration, Unacceptable.
Figure 1. SA Bus EOL Termination Scenarios
Note: The FX-BACEOL-0 RS485 End-of-Line Terminator module is not designed for EOL termination on the SA bus.