This is an eight-, four-, or two-port, asynchronous, serial communication board designed for use on the PC/104 bus. It supports RS-232, RS-422 or RS-485 communications. The board may be installed in any standard PC/104 stack. Connections are made via two 40 pin IDC type right angle connectors. Common applications include POS, gaming systems, machine monitoring, military and high-density networking. Type 16780 UARTS are used as the asynchronous communication elements. These include 64-byte transmit/receive FIFO buffers to protect against lost data in multitasking systems while maintaining 100% compatibility with the original IBM serial port (software compatible with Windows COM port drivers). A crystal oscillator located on the board permits precise baud rate capability up to 115,200. Higher speeds, up to 921.6K, are achieved by installing a jumper on the board. The addresses of the individual channels and IRQ are stored in non volatile memory on the board and loaded into programmed logic when the board is initially powered. AUTO TRANSCEIVER CONTROL In RS-485 multidrop communications individual drivers must be enabled when needed and then disabled after use to permit all ports on the network to share a two-wire or four-wire cable. The 104-COM-8SM and 104-COM4SM use an automatic (AUTO) control software selectable channel by channel. The driver is enabled (and the receiver disabled) when data is ready to be transmitted. When transmission is complete, the driver remains enabled for the transmission time of one additional character and then is disabled. This is ideal for use in Windows based applications as the standard Windows COM port driver is used to ensure compatibiliy. UTILITY SOFTWARE Tools provided include samples to demonstrate COM port initialization in multiple languages. Driver software is provided by Windows and all other major operating systems, including Linux (16550 compatible.) A graphical Setup program is provided to assist with jumper selections for protocol and address configuration.