The VW3A3E303 is a communication card from Schneider Electric that provides a Uni-Telway and Modbus RTU/ASCII interface for Altivar drives or other compatible devices. It connects via a 9-way female SUB-D connector and supports 2-wire or 4-wire RS485 physical layers at baud rates of 4800, 9600, or 19200 bps.
The RS485 physical interface (2-wire for Modbus, 4-wire for Modbus, or 2-wire for Uni-Telway) determines the wiring topology. A 2-wire half-duplex bus is standard for Modbus RTU; the 4-wire option supports full-duplex Modbus where needed. The card's data format flexibility — 7 or 8 bits, odd/even/no parity, 1 or 2 stop bits — lets it match the existing bus configuration without a protocol converter. The two LEDs (ERR for fault, RUN for status) and the graphic display terminal signals (control word received, reference received) give on-card diagnostics without a separate tool.