Diamond Systems EMM-8PL-XT 8-Channel RS-232/422/485 Serial Port PC/104 Module

Rugged PC/104 systems that talk to many serial devices can run out of ports long before they run out of stack space. The EMM-8PL-XT answers that with eight multiprotocol serial ports on one PC/104 module from the Diamond Systems Emerald-MM family, configured entirely in software, and it is a form, fit and function replacement for the earlier EMM-8P-XT.

The module is based on two industry-standard 16C654 quad UARTs, giving eight ports with 64-byte transmit and receive FIFOs at up to 115.2 kbps. I/O addresses and interrupt levels are programmable, any number of ports can share an interrupt, and each port can be enabled or disabled in software. Configuration data lives in on-board EEPROM and loads automatically at power-up, and four preset address groups can be fixed with jumpers where an application needs set addresses.

Each port on the EMM-8PL-XT is chosen in software for RS-232, RS-422 or RS-485, with local-echo and non-echo RS-485 modes and jumper-selectable termination for RS-422/485. Two 40-pin headers carry four serial ports and four digital I/O lines each, so the module also gives the stack eight digital lines with independently programmable direction. The only change from the EMM-8P-XT is the RS-232 limit of 115.2 kbps, against 460.8 kbps on the original, because its RS-232 transceiver reached end of life. The EMM-8PLUS-XT offers eight faster ports on PC/104-Plus, and the EMM-4M-XT has four ports on PC/104.

Power is 5 V DC only, at around 160 mA typical with outputs unloaded, so the stack needs no 12 V supply for serial operation. The EMM-8PL-XT operates from -40 to 85 °C, with a quoted MTBF of 490,500 hours, and drivers are available for Windows 10 and Linux.