Diamond Systems Emerald-MM-4M-XT 4-Port RS-232 and 48 Digital I/O PC/104 Module

The Diamond Systems Emerald-MM-4M-XT is a PC/104 embedded serial and digital I/O module delivering 4 configurable RS-232/RS-422/RS-485 serial ports and 48 channels of digital I/O in a compact form factor. Built around a 16C554 quad UART with 16-byte FIFOs per port, the module supports baud rates to 115.2 kbps standard, with optional 460.8 kbps operation. Engineered for industrial temperature ranges of −40°C to +85°C, it integrates jumper-selectable addressing and interrupt configuration for flexible system deployment.

## Technical Specifications

**Serial Interface**
• 4 ports, configurable via jumpers for RS-232, RS-422, or RS-485
• 16C554 quad UART with 16-byte FIFO per port
• Baud rates: up to 115.2 kbps (standard); up to 460.8 kbps with 7.3728 MHz crystal option
• RS-232: 8 signals + ground per port; RS-422: RX+, RX−, TX+, TX−, ground; RS-485: TX+/RX+, TX−/RX−, ground
• Dual 20-pin I/O headers (2 ports per header)
• 120 Ω termination resistors for RS-422/485, jumper-selectable

**Digital I/O**
• 48 channels organized as 6 × 8-bit ports
• Output current: 0.3 mA (high state), 8 mA (low state)
• Inverting logic with 10 kΩ pull-up resistors; tri-state on logic 1, driven low on logic 0
• Edge detection on 24 lines; independently selectable high/low edge per bit with interrupt generation

**Electrical & Environmental**
• Power supply: +5 V only
• Operating temperature: −40°C to +85°C

**Configuration**
• 8 jumper-selectable I/O address combinations; custom addressing available for OEM applications
• 10 interrupt levels: 2, 3, 4, 5, 6, 7, 10, 11, 12, 15; full interrupt sharing supported

## Key Features

• Quad UART with independent 16-byte buffering reduces CPU overhead
• Protocol flexibility via jumper configuration eliminates board redesign across RS-232/422/485 applications
• Edge-triggered interrupts on 24 DIO lines enable real-time event handling
• Interrupt sharing conserves ISA interrupt resources in multi-module systems
• Industrial temperature range supports extended deployment environments

## Typical Applications

• Embedded data acquisition in industrial controllers
• Multi-port serial concentrators in rugged systems
• Real-time digital event monitoring and logging
• Distributed I/O in PC/104 stacks

## Compatibility & Integration

PC/104 form factor; jumper-configurable for legacy and modern ISA interrupt schemes. Interrupt status register supports legacy and contemporary operating systems requiring per-port interrupt identification.