9.1.1 Device Configuration

The SN65HVD888 is a half-duplex RS-485 transceiver operating from a single 5-V ±10% supply. The driver and receiver enable pins allow for the configuration of different operating modes.

Figure 16. Transceiver Configurations

Using independent enable lines provides the most flexible control as the lines allow for the driver and the receiver to be turned on and turned off individually. While this configuration requires two control lines, it allows for selective listening to the bus traffic, whether the driver is transmitting data or not. Only this configuration allows the SN65HVD888 to enter low-power standby mode because it allows both the driver and receiver to be disabled simultaneously.

Combining the enable signals simplifies the interface to the controller by forming a single direction-control signal. Thus, when the direction-control line is high, the transceiver is configured as a driver, while for a low the device operates as a receiver.

Tying the receiver enable to ground and controlling only the driver-enable input also uses only one control line. In this configuration a node not only receives the data on the bus sent by other nodes but also receives the data sent on the bus, enabling the node to verify the correct data has been transmitted.