Diamond Systems EMM-8M-XT 8-Port RS-232/RS-422/RS-485 PC/104

The Diamond Systems EMM-8M-XT is a PC/104 serial communications module that provides eight independently configurable ports supporting RS-232, RS-422, and RS-485 protocols. Each port can be individually jumper-selected for its protocol, enabling flexible deployment across mixed-protocol industrial and embedded systems. The module integrates two 16C654 Quad UART ICs with 64-byte transmit and receive FIFOs per port, delivering deterministic throughput up to 460.8 kbps and minimizing processor overhead through interrupt-driven operation.

## Technical Specifications

**Serial Ports**
• 8 ports with user-selectable RS-232, RS-422, or RS-485 operation
• UART: Two 16C654 Quad UART ICs
• FIFO: 64-byte transmit and receive buffers per port
• Maximum Baud Rate: 460.8 kbps
• Data Bits: 5, 6, 7, or 8
• Parity: Even, odd, or none
• RS-232: Full complement of standard PC serial signals (8 signals + ground)
• RS-422: RX+, RX−, TX+, TX−, ground
• RS-485: TX+/RX+, TX−/RX−, ground
• I/O Headers: Two 40-pin connectors, ports grouped in sets of four

**Digital I/O**
• 8 individually programmable digital I/O lines

**Electrical**
• Power Supply: +5 VDC ±10%

**Physical**
• Form Factor: PC/104 (ISA)
• Weight: 2.6 oz (74 g)
• Connectors: Two 40-pin I/O headers

**Environmental**
• Operating Temperature: −40°C to +85°C

## Key Features

• Jumper-configurable protocols on all eight ports
• Software-programmable I/O base addresses and interrupt levels (IRQ 2, 3, 4, 5, 6, 7, 10, 11, 12, 15)
• Interrupt sharing across any number of ports or boards at identical levels
• Per-port interrupt status register
• Selectable 1 kΩ pulldown resistor per port
• Power-on default: all ports disabled until software configuration
• Optional hardware configuration for operation without software initialization

## Typical Applications

Industrial control systems, embedded computing platforms, legacy serial device integration, multi-protocol data acquisition, rugged field instrumentation.

## Compatibility & Integration

PC/104 ISA bus. All address and interrupt configuration performed in software or via hardware jumpers. Extended temperature rating (−40°C to +85°C) supports deployment in harsh industrial environments.