Diamond Systems EMM-OPT4-XT PC/104 Module with 4 Opto-Isolated Serial RS-232/422/485 Ports and GPIO

Trains and buses subject their electronics to ground differentials and noise spikes that can damage a non-isolated serial board, along with wide temperature swings. The EMM-OPT4-XT is a PC/104 module from the Diamond Systems Emerald-MM family that answers both, with four optically isolated RS-232/422/485 ports and 24 digital I/O lines on one board.

Each serial port is isolated to 1000 V AC or DC from the other ports and from the system. The 16C2850 UARTs with 128-byte FIFOs support data rates up to 230.4 kbps in RS-232 mode and 460.8 kbps in RS-422/485 mode without overloading the host processor, and auto-flow control enables and disables the RS-485 transmitter automatically to prevent bus conflicts. Each port is independently configurable for protocol and interrupt, with eight built-in I/O address combinations and interrupt sharing.

On the EMM-OPT4-XT every serial port has its own 10-pin connector, and jumper-selectable 150 ohm termination with pull-up and pull-down resistors suits the ends of RS-422 or RS-485 cables. The 24 digital I/O lines are based on an 82C55, with direction programmable in 4-bit and 8-bit groups and user-configurable 10 kΩ pull-up resistors, on a 26-pin header. Combining serial and digital I/O can save a board in the PC/104 stack. The EMM-4M-XT offers four non-isolated ports, and the EMM-8PL-XT offers eight.

The module runs from 5 V DC at around 300 mA typical with outputs open and uses the PC/104 16-bit bus with 8-bit data. The EMM-OPT4-XT operates from -40 to 85 °C, which Diamond Systems positions for vehicles such as trains and buses where temperature swings are routine. Diamond offers a DB9 cable for each serial port and a 26-way ribbon cable for the digital I/O.