Emerald-MM-8P offers 8 multi-protocol serial ports on a single PC/104 module with complete software configurability via the operating system. Each port can be individually selected for RS-232, RS-422, or RS-485 under software control. Both local-echo and non-local-echo modes are supported for RS-485. I/O addresses and interrupt levels are also programmable, with interrupt sharing available for any number of ports. Each port may further be enabled or disabled in software. All configuration data is stored in an on-board EEPROM that is loaded automatically on power-up.

For applications where fixed addresses are desired, four groups of preset addresses are available with jumper settings that override the programmed settings. Line termination for RS-422/485 modes is also jumper-selectable.

Emerald-MM-8P offers 8 convenient digital I/O lines. The direction of each line is independently programmable. Diamond’s Universal Driver software provides software support for these digital I/O lines.

Two I/O headers are provided, with four serial ports and four digital I/O lines 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-8P is based on the 16C654 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 64-byte transmit and receive FIFOs to support the high-speed 460.8kbps data rates. Model EMM-8P-XT is backward compatible with Diamond Systems’ EMM-8M-XT and EMM-8232-XT boards.


Interface8x RS-232, RS-422, RS-485 (local and no echo)
All features software configurable
Two 16C654 quad UARTs
5, 6, 7, or 8 data bits
Even, odd, or no parity
All outputs protected against continuous short circuit
RS-232Input impedance: 3KOhm minimum
Input voltage swing: ±30V maximum
Output voltage swing: ±5V min, ±7V typical
RS-422/485Differential: -0.2V min, +0.2V max input threshold
Input impedance: 12K Ohm minimum
Input current: +1.0mA max (VIN = 12V), -0.8mA max (VIN = -7V)
Differential output voltage: 2.0V min (RL=50 Ohm)
High/low states differential output voltage symmetry: 0.2V maximum
Data RatesUp to 115kbps standard
460.8kbps available via jumper selection
Address/IRQAvailable interrupt levels are 2, 3, 4, 5, 6, 7, 10, 11, 12, and 15
OtherDigital I/O
• Number of I/O lines: 8 in, 8 out
• Input voltage Low: -0.3V min, 0.8V max
• Output voltage Low: 0.0V min, 0.4V max (IOL = 6mA max)

EEPROM storage of configuration data
Connector(s)2 40-position (2x20) .025" square pin header on .1" center
Headers mate with standard ribbon cable (IDC) connectors


ExpansionStandard 16 bit PC/104 interface
8-bit and 16-bit bus stack through headers are installed
(16-bit header is used for interrupt levels only)
Electrical+5VDC ±10%
160mA typical, all outputs unloaded
MechanicalWidth: 96 mm x 90 mm, 3.55" x 3.775"
Conformal CoatingOn request
SoftwareStandard 16C554 UART on ISA bus - no additional software required
TemperatureTemperature range (operation): -40°C to +85°C
Temperature range (storage): -40°C to +85°C
Humidity5% to 95% noncondensing
Weight2.5oz (71g)
MTBFEMM-8P-XT: 490,502 hours
Warranty1 Year



Emerald-MM-8P 8-ch RS-232/422/485, PC/104, Extended Temperature
Quad DB9 male to 40-pin header 18" cable, serial ports 1-4 (uses 2)
Order OnlineDSC Emerald-MM-8P - Order Online
Recab UK
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