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Products   >   Services   >   End-of-Life Products   >   Emerald-MM-8 8-Port Serial Module
8 serial ports
8 digital I/O lines
Jumper selectable RS-232, RS-422, RS-485 on all ports
Up to 460.8kbps data rate
16C654 Quad UARTs with 64-byte FIFOs
Interrupt sharing - any number of ports or boards
Interrupt status register for Windows NT
Dual 40-pin I/O headers (4 ports per header)
16-bit PC/104 bus for additional interrupt levels
+5V only power supply
-40ºC to +85ºC operation
Customers who use this product also use:
4-port DB9 Serial Cable

This product can be customized and ruggedized. Click here for more information.
See Emerald-MM-8 8-Port Serial Module Technical Resources
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Emerald-MM-8 datasheet
(.pdf, 191.3 kb)
Emerald-MM-8 Manual
(.pdf, 606.6 kb)
Adding a serial port in Windows XP
(.doc, 363.5 kb)
Emerald-MM-8 Example Programs for UD 5.91
(.zip, 153.9 kb)

Emerald-MM-8 8-Port Serial Module

8-Port RS-232/RS-422/RS-485 PC/104 Module

Emerald-MM-8  8-Port Serial Module
click for a larger image
Flexible Configuration
I/O Headers
Emerald-MM-8 User Manual (HTML Version)
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The Emerald-MM-8 gives you 8 serial ports on a single PC/104 module operating at speeds up to 460.8kbps.

In RS-232 mode, the full complement of standard PC serial port signals (8 signals + ground) are provided for each port. In RS-422 mode, Signals RX+, RX-, TX+, and TX- are provided, along with ground. In RS-485 mode, signals TX+/RX+ and TX-/RX- are provided, along with ground. Ports are grouped 4 per 40-pin I/O header. Ports 1-4 are on the right, and ports 5-8 are on the left.

Two 16C654 quad serial port ICs are used for the serial ports. This chip supports data rates up to 460.8kbps and contains a 64-byte transmit and receive FIFOs for each port to minimize processor overhead.

Fully Programmable Serial Ports

All serial port address and interrupt level settings may be done in software. On power up, the serial ports are disabled. After programming the address and interrupt settings, the ports are enabled by setting a bit in an auxiliary control register. For applications that require the ports to be operating without user software intervention, the board provides 4 different hardware configurations.

Full Interrupt Sharing

Interrupt levels are individually programmable 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 and is selected with a jumper. 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.

8 Digital I/O Line

Emerald-MM-8 has 8 programmable digital I/O lines. Each line can be independently programmed for input or output.

Designed for the Embedded World

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 (-40°C to +85°C) is also standard.

Flexible Configuration

Emerald-MM-8 provides a 4-byte register map that provides access to all the board's features. The address of this map is selected with jumpers. Programming of the I/O addresses and interrupt levels of the 8 ports is then done through these registers:

Base + Write Function Read Function
0 Select address or interrupt register to write Read back selected register no.
1 Write address or interrupt to selected register Read back port 1 address (diagnostic)
2 Digital I/O direction register Interrupt status register
3 Digital output register Digital input register

I/O Headers

Emerald-MM-8 has two 40-pin I/O headers with two serial ports on each header. These headers mate with standard ribbon cable connectors. Our cable no. C-DB9M-4 provides a 40-pin IDC connector at one end to mate with the pin headers on the board, and it has four DB-9 male connectors at the other end with the standard PC serial port pinout. Each cable handles four ports; two cables provide access to all eight ports on the board.

The pinouts shown below apply to any port when in the stated mode. Depending on which version of the board you have, certain pinouts may not apply. Please note that for simplicity only ports 1 through 4 are shown, and all ports are shown in the same configuration. However each port can be configured independently.

DCD 1 1 2 DSR 1
RXD 1 3 4 RTS 1
TXD 1 5 6 CTS 1
DTR 1 7 8 RI 1
GND 9 10 DIO 1
DCD 2 11 12 DSR 2
RXD 2 13 14 RTS 2
TXD 2 15 16 CTS 2
DTR 2 17 18 RI 2
GND 19 20 DIO 2
DCD 3 21 22 DSR 3
RXD 3 23 24 RTS 3
TXD 3 25 26 CTS 3
DTR 3 27 28 RI 3
GND 29 30 DIO 3
DCD 4 31 32 DSR 4
RXD 4 33 34 RTS 4
TXD 4 35 36 CTS 4
DTR 4 37 38 RI 4
GND 39 40 DIO 4

RS-422 Mode

N/C 1 2 N/C
TXD+ 1 3 4 TXD- 1
GND 5 6 RXD- 1
RXD+ 1 7 8 N/C
GND 9 10 DIO 1
N/C 11 12 N/C
TXD+ 2 13 14 TXD- 2
GND 15 16 RXD- 2
RXD+ 2 17 18 N/C
GND 19 20 DIO 2
N/C 21 22 N/C
TXD+ 3 23 24 TXD- 3
GND 25 26 RXD- 3
RXD+ 3 27 28 N/C
GND 29 30 DIO 3
N/C 31 32 N/C
TXD+ 4 33 34 TXD- 4
GND 35 36 RXD- 4
RXD+ 4 37 38 N/C
GND 39 40 DIO 4

RS-485 Mode

N/C 1 2 N/C
TX/RX+ 1 3 4 TX/RX- 1
GND 5 6 N/C
N/C 7 8 N/C
GND 9 10 DIO 1
N/C 11 12 N/C
TX/RX + 2 13 14 TX/RX- 2
GND 15 16 N/C
N/C 17 18 N/C
GND 19 20 DIO 2
N/C 21 22 N/C
TX/RX+ 3 23 24 TX/RX- 3
GND 25 26 N/C
N/C 27 28 N/C
GND 29 30 DIO 3
N/C 31 32 N/C
TX/RX+ 4 33 34 TX/RX- 4
GND 35 36 N/C
N/C 37 38 N/C
GND 39 40 DIO 4


Serial Ports
Number of serial ports 8
Protocol RS-232, RS-422, and/or RS-485
Maximum baud rate 460.8kbps
Communications parameters 5, 6, 7, or 8 data bits;
Even, odd, or no parity
Base address options Programmable
Interrupt level options Programmable; select from levels 2 (9), 3, 4, 5, 6, 7, 10, 11, 12, 15
RS-232 Characteristics:
Input voltage swing ±30V maximum
Input thresholds
Logic 0: 0.8V min
Logic 1: 2.4V max
Input impedance 3KΩ minimum
Output voltage swing ±5V min, ±7V typical
Output resistance 300Ω minimum
RS-422/RS-485 Characteristics:
Differential input threshold -0.2V min, +0.2V max
Input impedance 12KΩ minimum
Input current +1.0µA max (VIN = 12V)
-0.8µA max (VIN = -7V)
Differential output voltage 2.0V min (RL=50Ω)
High/low states
differential output voltage symmetry
0.2V max differential
Short circuit protection All outputs protected against continuous short circuit
I/O header 2 40-position (2x10) .025" square pin header on .1" centers;
Headers mate with standard ribbon cable (IDC) connectors
Dimensions 3.55" x 3.775"
Weight 2.60z / 74g
Power supply +5VDC ±10%
Current consumption 80mA typical, all outputs open
Operating temperature -40°C to +85°C standard, all versions
Operating humidity 5% to 95% noncondensing
PC/104 bus 8-bit and 16-bit bus headers are used (16-bit header is used for interrupt levels only)
MTBF EMM-8M-XT 288,849 hours
RoHS Compliant

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Emerald-MM-8 8-Port Serial Module
available models:
Emerald-MM 8-ch RS-232/422/485 extended temperature
Minimum Order Quantity of 50
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