Part# 3540

The 3540 is the first PC/104 serial interface module to provide four software-selectable RS-232, RS-422, or RS-485 ports. RS-232, RS-422, or RS-485 mode may be selected independently via software command for each of the four ports, eliminating the need for setting jumpers or DIP switches. The board is designed using the XR16C864 UART, which provides a 128-byte FIFO, 8 times larger than boards designed with 16C550 compatible parts. The larger buffers allow error free operation even in high-speed applications. In RS-485 mode the C4-104.ULTRA offers automatic control of the RS-485 driver enable for trouble free network master arbitration. Additionally, the C4-104.ULTRA allows RS-485 network termination, critical to robust multi-drop communication, to be selectively added to the circuit via a simple software command.