SLLSF86C May 2018 – March 2022
PRODUCTION DATA
The ISOW14x2 devices are designed for bidirectional data transfer on multipoint RS-485 networks. An RS-485 bus has multiple transceivers that connect in parallel to a bus cable. Both cable ends are terminated with a termination resistor, RT, to remove line reflections. The value of RT matches the characteristic impedance, Z0, of the cable. This method, known as parallel termination, lets higher data rates be used over a longer cable length.
Full-duplex implementation shown in Figure 9-1 requires two signal pairs (four wires). Full-duplex implementation lets each node to transmit data on one pair while simultaneously receiving data on the other pair.
Figure 9-2 below, shows ISOW14x2 devices used in half duplex configuration. Driver outputs Y and Z are shorted to A and B respectively. This reduces overall cabling requirements. Also DE/RE are shorted to each other, and at a time, any node acts as either a driver or a receiver. Split termination is also shown in this configuration which helps to boost network immunity in noisy environments by providing common-mode noise filtering and also reduces radiated emissions by providing low impedance path to earth to the bus common mode excursions.