The PMC-SIO4AR-SYNC is a four channel full-duplex RS-422/485 serial board with Rear I/O. Each channel can operate up to 8 Mbits/sec. Optional 32 Kbyte FIFO buffer for both transmit and receive (256 Kbytes Total FIFOs) data on each channel provides for a smooth and efficient interface between the serial interfaces and the PMC host computer. The card features a simple 3 signal interface utilizing a clock, data and an enable.