Skip to main content

Diamond Systems EMM-8PLUS-XT

PC/104-Plus 8-Port RS232/422/485 Serial I/O Module

Things Embedded are an official Diamond Systems UK distributor and can supply the EMERALD-MM-8PLUS.


Serial I/O


Diamond Systems


The Emerald-MM-8Plus from Diamond Systems 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.

Diamond Systems’ 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.


Brand & Model Diamond Systems EMM-8PLUS-XT
PC/104-Plus 8-Port RS232/422/485 Serial I/O Module
Features Compact
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/RS-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 differentia 0.2V max
output voltage symmetry
Digital I/O
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 2 40-position (2×20) .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
Operating temperature -40°C to +85°C standard, all versions
Weight 3.1oz (87.9g)
RoHS Compliant

Need Help Choosing Serial I/O?

Tell us about your application and a member of the team will get right back to you.