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High Performance PC/104-Plus 8 Port RS232/422/485 Serial I/O Module
  • Details
  • Specification
  • Order information
  • Number of serial ports: 8
  • Protocols: RS-232, RS-422, RS-485
  • Digital I/O lines: 8 individually programmable
  • Operating temperature: -40°C to +85°C standard, all versions

Emerald-MM-8Plus is a high performance multi-protocol serial communications board offering eight ports on a single PC/104-Plus module. Supporting baud rates up to 921.6K bps in RS-232 mode or 1.8432Mbps in RS422 or RS485 mode, each port can be individually selected for RS-232, RS-422, RS-485 or TTL level operation. Both local-echo and non-local-echo modes are supported for RS-485. Protocol selection is achieved via a jumper block for each of the eight ports. Line termination for RS-422/485 modes is also jumper-selectable.

Configuration of the Emerald-MM-8Plus is simple, using the built-in plug and play technology. For manual configuration, the base address for the board may be set in software, defining a 4K block of configuration space used to access the on-board registers. A single 32-bit read shows the detailed interrupt status for each of the eight ports. The PCI «slot» is defined through a jumper block. As with all Diamond Systems products, jumpers are paralleled with locations for zero ohm resistors to create a rugged, shock-and- vibration-resistant implementation.

Emerald-MM-8Plus is based on the Exar 17D158 octal UART IC. This device contains 8 4 identical sets of 16C55registers, 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 data rates.

Emerald-MM-8Plus also offers 8 convenient digital I/O lines. The direction of each line is independently programmable. Finally, Emerald-MM-8Plus also offers a 16-bit programmable counter / timer with a configurable clock source.

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.

Operating Systems Compatibility
The Emerald-MM-8Plus is compatible with Windows 98/NT/2000/XP and Linux. If using Exar’s default Vendor and Device ID, you can use Exar’s module driver for Linux kernels 2.4.x and Linux kernels 2.6.1-2.6.7. Linux kernels 2.6.8 and newer have support in the kernel for the XR17×15x PCI UARTs. See the «8250_pci.c» in the kernel. If using your own Vendor and Device ID, you can use the module driver available from Exar after you modify the Vendor and Device ID accordingly in the module driver.

Technical specifications

Serial ports

Number of serial ports 8
Protocols RS-232, RS-422, RS-485 (local and no echo)
Protocol Configuration Jumpers
Software Configuration Plug and Play
Maximum baud rate 1.8432Mbps
Communications parameters 5, 6, 7, or 8 data bits; Even, odd, or no parity
Short circuit protection Continuous, all outputs

RS-232 mode

Input Impedance 3KΩ min
Input voltage swing ±30V maximum
Output voltage swing ±5V min, ±7V typical

RS-422/485 modes

Differential input threshold -0.2V min, +0.2V max
Input impedance 12KΩ minimum
Input current +1.0mA max (Vin = 12V)
-0.8mA max (Vin = -7V)
Differential output voltage 2.0V min (RL=50Ω)
High/low states differential output voltage symmetry 0.2V max


Number of I/O lines 8 individually programmable
Input voltage Logic 0: -0.3V min, 0.8V max
Logic 1: 2.0V min, 5.3V max
Output voltage 0: 6mA max
1: -4mA max


I/O header 2x 40-position (2x20) .025" square pin header on .1" centers;
Headers mate with standard ribbon cable (IDC) connectors
Dimensions 3.55" x 3.775"
Power supply +5VDC ±10%
Current consumption 160mA typical, all outputs unloaded
Weight 3.1oz (87.9g)

Environmental and physical specifications

Operating temperature -40°C to +85°C standard, all versions
Rohs Compliant
Model Description
EMM‑8PLUS‑XT Emerald-MM RS-232/422/485 x8 PC/104-Plus Module
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