Diamond Systems Emerald-MM-Opto

Adds Four RS232c, RS422 or RS485 Interfaces to PC/104 Bus, 1000v Isolation


Emerald-MM-Opto provides an integrated, rugged, and reliable solution for PC/104-expandable embedded systems requiring serial communications in demanding applications. It offers 2 or 4 optically isolated serial ports with RS-232, RS-422, and RS-485 protocols, as well as 24 digital I/O lines, all on a single board.

Optical isolation of 1000V DC or AC protects your embedded system from ground differentials or noise spikes that would damage non-isolated boards. Each port is isolated from the other ports as well as the system. Extended temperature capability (-40 to +85ºC) enables the board to operate in vehicles such as trains and buses without concern for temperature swings. These features enable Emerald-MM-Opto to provide reliable serial communications in harsh environments such as trains and buses.

In addition to ruggedness, Emerald-MM-Opto offers flexibility and advanced features. Each serial port is independently configurable for protocol and IRQ settings. Eight different I/O address combinations are built-in. The 16C2850 UART chips with 128-byte FIFOs support high-speed data rates at up to 460kbps without overloading the system processor. Auto-flow control enables easy RS-485 operation by automatically enabling and disabling the transmitter during data transmission, to prevent bus conflicts or excessive software overhead.

Emerald-MM-Opto also offers multiple termination methods on the serial ports to support varying interface requirements. In RS-422 or RS-485 networks, termination resistors are normally installed at the endpoints of the cables to minimize reflections on the lines. The board provides jumper-selectable termination and pull-up/pull-down resistors for this purpose. The sensible jumper positioning and layout help simplify board configuration and minimize confusion.

The 24 digital I/O lines are based on an 82C55 chip and feature programmable direction in 4- and 8-bit groups. All I/O lines contain user-configurable 10K Ohm pull-up resistors for convenience. This 2-in-1 combination of serial ports and digital I/O can help lower the size and cost of your embedded system by eliminating one additional board from your PC/104 stack.

Diamond Systems offers appropriate mating cables for your convenience. Cable no. C-DB9M-1 provides a DB-9 male connector with a standard PC serial port pinout. Each serial port requires one cable. Cable no. C-26-18 is a 26-conductor ribbon cable for the digital I/O lines.


Interface4x RS-232, RS-422, RS-485 (jumper selected)
8 pre-configured standard I/O address options; custom addresses available
16C2850 with 128-byte FIFO and auto-flow control
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: 12KOhm minimum
Input current: +1.0µA max (VIN = 12V), -0.8µA max (VIN = -7V)
Differential output voltage: 2.0V min (RL=50 Ohm)
High/low states differential output voltage symmetry: 0.2V maximum
Data RatesRS-232: Up to 230.4 kbps max
RS-422/485: Up to 460.8 kbps max
Address/IRQAvailable interrupt levels are 2, 3, 4, 5, 6, 7, 10, 12, 15
Interrupt sharing supported
OtherIsolation: 1000V AC or DC, port to port or port to the system
Termination: 150? with 1K? pull-up/pull-down
24 programmable direction using 82C55
Connector(s)Individual 10-pin connector for each serial port (.025" square pin header on .1" centre)
Digital I/O: 26-pin connector for digital I/O


ExpansionStandard 16 bit PC/104 interface (8-bit data)
8-bit and 16-bit bus stack through headers are installed
Electrical+5VDC ±10%
300mA typical consumption, all outputs unloaded
MechanicalWidth: 96 mm x 90 mm, 3.55" x 3.775"
Conformal CoatingOn request
SoftwareStandard 16C2850 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
Weight3.0oz / 85g
Warranty1 Year



Emerald-MM-OPTO 4 Opto-Isolated RS-232/422/485 + 24 Digital I/O
Single DB9 male to 10-pin header 18" cable (uses 4)

Dual 26-pin connectors, 18 inches
Diamond Systems Emerald-MM-Opto - order online
Recab UK
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