Diamond Systems Emerald-MM

Adds 4 RS232c, RS422 or RS485 Interfaces to PC/104 Bus


Diamond Systems' Emerald-MM PC/104 module gives you 4 serial ports operating at speeds up to 115kbps.

In RS-232 mode, the full complement of standard PC serial port signals (8 signals + ground) are provided for each port and are grouped onto two 20-pin headers (2 ports per header). In RS-422 mode, Signals RX+, RX-, TX+, and TX- are provided, along with the ground. In RS-485 mode, signals TX+/RX+ and TX-/RX- are provided, along with the ground.

A 16C554 quad serial port IC is used for the serial ports. This chip supports data transfer rates up to 115kbps and contains a 16-byte programmable FIFO buffer for each port to minimize processor overhead.


Emerald-MM offers more interrupt level and I/O address options than other quad serial port modules. Therefore, integrating the board into your computer system is a simpler task. Eight different I/O address combinations and 10 different interrupt levels are available.


Any number of ports can share the same interrupt level. And if you have two boards in one system, both boards can share the same interrupt level as well. An interrupt status register is provided to indicate the status of each serial port's interrupt request signal. This register is especially useful in Windows NT.


Another distinguishing feature of Emerald-MM is its low-power +5V only operation. This board needs absolutely no +12V or -12V to operate. Extended temperature operation of -40°C to +85°C is also standard.


Interrupt levels are individually selectable for each port. The available interrupt levels are 2, 3, 4, 5, 6, 7, 10, 11, 12, and 15. In addition, a 1K Ohm pulldown resistor is provided for each port.

A single interrupt level can be shared by 2, 3, or 4 ports on one board and can even be shared by more than one board in the system. To enable interrupt sharing, set two or more interrupt level jumpers to the same level and pull out all but one pulldown resistor jumper.


Emerald-MM has two 20-pin I/O headers with two serial ports on each header. These headers mate with standard ribbon cable connectors. The cable no. C-DB9M-18 provides a 20-pin IDC connector at one end to mate with the pin headers on the board, and it has two DB-9 male connectors at the other end with the standard PC serial port pinout. Each cable handles two ports; two cables provided


Interface4x RS-232, RS-422, RS-485 (jumper selected)
16C554 quad UART
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: 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 Rates115kbps standard version
460.8kbps available (EMM-HS-XT)
Address/IRQAvailable interrupt levels are 2, 3, 4, 5, 6, 7, 10, 11, 12, and 15
Connector(s)2 20-position (2x10) .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
Electrical+5VDC ±10%
80mA typical consumption, 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
MTBFEMM-4M-XT: 555,428 hours
Warranty1 Year



Emerald-MM 4-ch RS-232/422/485, PC/104, Extended Temperature
Dual DB9 male to 20-pin header 18" cable (uses 2)
Diamond Systems Emerald-MM - order online
Recab UK
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