Diamond Systems EMM-4M-XT 4-Port RS-232/422/485 Serial PC/104 Wide Temperature Module

Some PC/104 systems need only a few serial ports, but they need them to behave exactly like standard PC serial ports and to fit around whatever addresses and interrupts the rest of the stack already uses. The EMM-4M-XT is a four-port serial module from the Diamond Systems Emerald-MM family for the ISA-bus PC/104 stack, with each port jumper-configured for RS-232, RS-422 or RS-485.

The module uses the industry-standard 16C554 UART, which is compatible with all popular embedded operating systems, at rates up to 230.4 kbps. Eight I/O address combinations and 10 interrupt levels make it easier to slot into an existing system. Any number of ports can share one interrupt level, two boards in one system can share an interrupt as well, and an interrupt status register reports the request status of each port.

In RS-232 mode each port on the EMM-4M-XT provides the full complement of standard PC serial port signals, eight signals plus ground. RS-422 mode provides transmit and receive pairs, and RS-485 mode a single transmit/receive pair, each with ground. The four ports are grouped on two 20-pin headers, two ports per header, and Diamond’s C-DB9M-18 cable breaks each header out to two DB9 male connectors. The EMM-8PL-XT doubles the port count with software configuration, and the EMM-OPT4-XT adds optical isolation.

Power is 5 V DC only, at around 80 mA typical with outputs unloaded. The EMM-4M-XT operates from -40 to 85 °C as standard, has both the 8-bit and 16-bit PC/104 bus headers installed with an 8-bit data bus, and carries a quoted MTBF of 555,000 hours. Every output is protected against continuous short circuit.