Emerald-MM

Emerald-MM is a PC/104 format I/O module with 4 serial ports. The board is available in multiple versions with different combinations of protocols:

EMM-XT 2 ports configurable for RS-232, RS-422, or RS-485; 2 ports fixed RS-232
(standard configuration)
EMM-4M-XT 4 ports configurable for RS-232, RS-422, or RS-485
EMM-4232-XT 4 ports fixed in RS-232
EMM-4485-XT 4 ports configurable for RS-422 or RS-485 (special order)
EMM-1W-XT 4 ports fixed RS-232; port 1 has 1-Wire interface (special order)

Eight different I/O address combinations can be selected, and 10 different interrupt levels can be assigned to configure each port, allowing operation as COM1 through COM4 as well as many other settings. Two I/O headers are provided, with two serial ports on each header. The board operates on +5V only, eliminating the need for a +12V supply that is often required for serial port operation.

Emerald-MM is based on the 16C554 quad serial port IC. This device contains 4 identical sets of registers, one for each port, and is compatible with the standard PC serial port. Each port contains a 16-byte FIFO.