1. Product Overview

Product Name: PCIe 4-Port 2×RS232 + 2×Isolated RS422/485 Card
Model: A124-I
Series: APCIe Advanced PCIe Serial Communication Card Series
Article Number: A124-I
Manufacturer: Rayon Technology Co., Ltd.
Manufacturer Address: 2F, No. 177, Chung Shan 2 Rd., Lu Chou City, Taipei Hsien, Taiwan
Contact: Tel: +886-2-82858362 | Fax: +886-2-82857065
Email: rayon@ms1.hinet.net
Websites: [www.rayontech.com](http://www.rayontech.com), [www.computex.com.tw/rayon](http://www.computex.com.tw/rayon)

The Rayon A124-I is a professional-grade PCI Express (PCIe) serial communication interface card designed for industrial and embedded control systems requiring mixed RS232 and isolated RS422/RS485 connectivity. It provides four independent serial ports—two standard RS232 ports and two ground-isolated RS422/RS485 ports selectable via DIP switch—offering flexible communication options for a wide range of industrial automation, instrumentation, and data acquisition applications.

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2. Key Features

- Four Independent Serial Ports: Two RS232 ports (Port A & B) and two isolated RS422/RS485 ports (Port C & D).
- Selectable Interface Modes: RS422 or RS485 modes selectable per port via DIP switch.
- Ground Isolation: Ports C and D feature galvanic isolation to prevent ground loops and protect connected equipment from electrical noise and surges.
- High-Performance Controller: Each port is managed by a Moschip MCS9904 serial communication controller, providing robust and reliable data handling.
- Wide Baud Rate Range: Supports baud rates from 50 bps to 115,200 bps, configurable per port.
- Plug & Play PCIe Interface: Fully compliant with PCI Express bus architecture; I/O, memory, and IRQ resources automatically assigned by the PCI BIOS.
- ADDC (Auto Data Direction Control): Built-in ADDC feature for RS485 mode ensures automatic transmit/receive direction control without software intervention.
- Industrial-Grade Design: Engineered for industrial control environments with extended temperature and humidity tolerance.
- Comprehensive OS Support: Compatible with Windows 2000, XP, Vista, Windows 7, and Linux operating systems.
- Flexible Cabling Options: Includes DB37 female connector and DB37-to-4×DB9 male cable; optional DB37-to-4×DB25 male cable available.
- Compact PCIe Form Factor: Standard PCIe bracket with 120 × 105 mm PCB dimensions.
- Enhanced System Efficiency: 128-byte transmit and receive FIFO buffers per port reduce CPU interrupt load and improve throughput.
- Ideal for Industrial Automation: Suitable for SCADA systems, PLC communication, CNC machines, and serial device networking.

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3. Technical Specifications

Controller: Moschip MCS9904 (PCIe to multi-serial controller)
Bus Interface: PCI Express (PCIe) x1 slot, plug & play configuration
Number of Ports: 4 total
- Port A & B: RS232
- Port C & D: Isolated RS422/RS485 (selectable via DIP switch)

Baud Rate: 50 bps to 115,200 bps (software programmable)
Flow Control: XON/XOFF (software) and RTS/CTS (hardware)
FIFO Buffer: 128 bytes transmit and receive per port
Connector Type: DB37 female on card
Cable Options:
- Included: DB37 male to 4×DB9 male (P485 cable)
- Optional: DB37 male to 4×DB25 male (A400 cable)

Dimensions: 120 mm (L) × 105 mm (W)
Bracket: Standard PCIe bracket
Material: Industrial-grade PCB with EMI shielding and gold-plated edge connector
Weight: Approx. 120 g (card only)

Environmental Conditions:
- Operating Temperature: 0°C to 55°C
- Storage Temperature: 0°C to 65°C
- Operating Humidity: 10% to 95% RH (non-condensing)
- Storage Humidity: 5% to 95% RH (non-condensing)

Electrical Isolation:
- Isolation Voltage: Ground isolation on RS422/RS485 ports (C & D)
- Isolation Type: Optical/electrical isolation between system ground and external device ground

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4. Functionality

The A124-I operates as a PCIe-based serial expansion card that adds four independent communication ports to a host PC or industrial computer. Ports A and B provide standard RS232 interfaces for local device connections such as modems, barcode scanners, or serial consoles. Ports C and D are configurable as RS422 or RS485 interfaces, each with galvanic isolation to protect against voltage differences and electrical noise in long-distance or industrial environments.

RS422 Mode:
- Full-duplex differential signaling for point-to-point or multi-drop communication.
- Suitable for long-distance, high-speed data transmission with noise immunity.

RS485 Mode:
- Half-duplex differential signaling for multi-drop bus networks.
- Auto Data Direction Control (ADDC) automatically manages transmit/receive switching, eliminating the need for manual RTS control.

Use Cases and Applications:
- Industrial automation and process control systems
- SCADA and DCS communication networks
- CNC machine interfaces
- Data acquisition and instrumentation systems
- Serial device servers and converters
- Embedded control systems requiring mixed RS232 and RS485 connectivity

Compatibility:
- Fully compatible with PCI Express x1/x4/x8/x16 slots
- Supported operating systems: Windows 2000, XP, 2003, Vista, Windows 7, and Linux (kernel 2.6.x and later)
- Compatible with Moschip MCS9904 driver suite for Windows and Linux

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5. Components & Accessories

Included Items:
- A124-I PCIe 4-Port Serial Card (DB37 female connector)
- P485 cable: DB37 male to 4×DB9 male connectors
- User manual and driver CD (Windows and Linux drivers)

Optional Accessories:
- A400 cable: DB37 male to 4×DB25 male connectors
- RS4232-4 or RS4232-8 isolated converter boxes for extended isolation and signal conversion
- TB485 terminal block adapter for RS485 wiring (DATA+, DATA−, GND)
- Replacement low-profile PCIe bracket (optional for compact systems)

Connectors:
- DB37 female on card
- DB9 male or DB25 male connectors on expansion cable
- Pin assignments conform to standard RS232 and RS422/RS485 signal definitions (see Appendix A-2 to A-4)

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6. Installation & Setup

System Requirements:
- Available PCI Express slot (x1 or higher)
- Supported OS (Windows 2000/XP/Vista/7 or Linux)
- Administrator privileges for driver installation

Installation Procedure:
1. Power off the host system.
2. Insert the A124-I card into an available PCIe slot.
3. Secure the card with the bracket screw.
4. Connect the DB37 expansion cable to the card’s connector.
5. Attach serial devices to the DB9 or DB25 connectors as required.
6. Power on the system.
7. Install the appropriate driver from the provided CD or download from Rayon’s website.
8. Verify installation via Device Manager (Windows) or `/dev/tty2[1–4][a–d]` devices (Linux).

DIP Switch Configuration:
- SW1 DIP switch controls interface mode for ports C and D.
- Bit 3: Port C (OFF = RS485, ON = RS422)
- Bit 4: Port D (OFF = RS485, ON = RS422)
- Bits 1 and 2 are unused.
- Default setting: RS485 mode for both ports C and D.

Cabling Notes:
- Use P485 cable for DB9 connections or A400 cable for DB25 connections.
- For RS485 mode, short DB9 pins 2–3 (DATA+) and 4–6 (DATA−).
- Ensure proper termination resistors (120 Ω) at both ends of RS485 bus.

Driver Installation:
- Windows: Plug & Play detection; install Moschip MCS9904 driver manually if not auto-detected.
- Linux: Extract driver package, run installation script (`Install.redhat`), select card type (APCIe/MPe9904), rebuild kernel modules, and reboot.

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7. Performance & Capabilities

Data Rate: 50–115,200 bps per port (software programmable)
Buffering: 128-byte transmit and receive FIFO per port
Interrupt Handling: PCI BIOS assigns IRQs automatically; supports IRQ sharing
Throughput Optimization: Reduced CPU interrupt frequency via buffered I/O
Signal Integrity: Differential signaling for RS422/RS485 ensures high noise immunity
Isolation Protection: Ground isolation prevents signal interference and equipment damage
Latency: Low-latency communication suitable for real-time control applications
Limitations:
- RS485 mode supports half-duplex communication only
- RS422 mode supports full-duplex but limited to point-to-point or small multi-drop networks
- Maximum cable length depends on baud rate and cable quality (typically up to 1200 m for RS422/RS485)

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8. Standards & Compliance

Bus Interface Standard: PCI Express Base Specification compliant
Serial Communication Standards:
- RS232 (EIA/TIA-232-F)
- RS422 (EIA/TIA-422-B)
- RS485 (EIA/TIA-485-A)

Electrical Isolation: Meets industrial isolation standards for ground separation
EMC Compliance: Designed for EMI/RFI resistance in industrial environments
Operating System Drivers:
- Windows 2000/XP/Vista/7 (32/64-bit)
- Linux kernel 2.6.x and later
Regulatory Compliance:
- CE and FCC Class A (industrial environment)
- RoHS compliant (lead-free manufacturing)

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9. Additional Information

Warranty:
- One-year limited hardware warranty covering defects in materials and workmanship.
- Excludes damage from misuse, electrical surges, or unauthorized modifications.
- Out-of-warranty repairs available at a flat-rate service charge.

Support & Maintenance:
- Technical support via email (rayon@ms1.hinet.net).
- Driver updates and documentation available on Rayon’s website.
- RMA (Return Material Authorization) required for repairs; contact Rayon Service Center for RMA number and return instructions.

Maintenance Recommendations:
- Avoid inserting or removing the card while the system is powered on.
- Keep connectors clean and free of dust.
- Ensure proper grounding and shielding in industrial installations.
- Periodically verify driver updates for OS compatibility.

Related Products in the APCIe Series:
- A102: 2-port isolated RS232 PCIe card
- A132: 2-port RS422/RS485 PCIe card
- A112: 2-port RS232/RS422/RS485 PCIe card
- A104: 4-port RS232 PCIe card
- A134: 4-port RS422/RS485 PCIe card
- A114: 4-port RS232/RS422/RS485 PCIe card
- A134I: 4-port isolated RS422/RS485 PCIe card
- A168: 8-port RS232 PCIe card
- A138: 8-port RS422/RS485 PCIe card
- A118: 8-port RS232/RS422/RS485 PCIe card

Complementary USB and Network Devices:
- UTS004: USB to 4-port isolated RS422/485 converter
- UTS485: USB to 2×RS232 + 2×isolated RS422/485 converter
- APORT080: IP-to-Serial converter with 8 isolated RS232 ports
- S432io: Serial port sharer with 1 master and 3 slave ports (RS422/485 and RS232)
- TWIN232 / TWIN485: Industrial isolated RS232/RS422/RS485 converters and repeaters

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Summary

The Rayon A124-I PCIe 4-Port Serial Card is a robust, industrial-grade communication interface designed for systems requiring both standard RS232 and isolated RS422/RS485 connectivity. Its combination of high-performance Moschip MCS9904 controllers, flexible DIP switch configuration, and comprehensive OS support make it ideal for industrial automation, control, and data communication applications. With ground isolation, ADDC functionality, and plug-and-play PCIe integration, the A124-I ensures reliable, interference-free serial communication in demanding environments while maintaining ease of installation and configuration.