XYCOM XVME-428/2 Product Description

I. Product Overview

XVME-428/2 is a 6U dual-high VMEbus intelligent asynchronous serial communication module (IASCM) launched by XYCOM (now under Pro-face). It is an enhanced version of XVME-428/1. The core difference lies in full-channel isolation and stronger driving capability. It is equipped with an onboard 68000 processor and intelligent I/O core, specifically designed for communication in VME architecture environments with multiple serial ports, high isolation, long distance, and strong interference. It provides 8 independent isolated programmable serial ports and is suitable for industrial automation, process control, military, rail transportation, and upgrading of old VME systems. This module has been officially discontinued and is mainly available in second-hand, refurbished, and inventory spare parts in the market. 

Core positioning

As a VMEbus intelligent slave device, the XVME-428/2 focuses on "8-channel isolated serial ports + four interface compatibility + on-board CPU burden reduction for the host + high-speed programmable baud rate + 500V electrical isolation + intelligent line editing + industrial-grade high reliability". It features high-density integration of multi-channel isolated communication capabilities in a single slot, autonomously processing serial port transmission and reception, protocol conversion, and data caching through onboard firmware. Each channel has independent electrical isolation, completely blocking ground loop interference, significantly reducing the load on the main CPU, and addressing the core pain points of centralized access of multiple serial devices in strong interference environments and long-distance reliable communication.

Two. Core functional characteristics

1. Standard VMEbus interface (fully compatible with intelligent slave devices)

Completely adheres to the IEEE 1014 VMEbus specification, compatible with all 6U VME chassis and backplanes, operating in intelligent slave device mode, supporting A16/A24 address space, fixedly occupying the short address space 0x03800–0x038FF, the base address can be flexibly configured through jumpers to avoid system address conflicts. Data width is compatible with D08/D16, compatible with 8/16-bit VME master controllers, backplane connections use P1/P2 connectors, supports VME standard interrupts and system fault signals (SYSFAIL), compatible with 21-slot VME chassis, plug-and-play.

2. 8 independent isolated programmable asynchronous serial channels (core function)

Equipped with dedicated serial controllers and 500V optical isolation circuits, providing 8 completely independent, electrically isolated, and software-programmable asynchronous serial interfaces (channels 0–7), each channel can be independently configured as RS-232C (short distance), RS-422A (full-duplex differential), RS-485 (half-duplex differential) or TTL level (four modes), with complete electrical isolation between channels, no ground loop interference, and capable of simultaneously connecting different interface types of serial devices (such as terminals, printers, PLCs, sensors, Modems).

Baud rate range: supports 300 bps–3 Mbps programmable, default 9600 bps, each channel independently set, compatible with low-speed instruments to high-speed data transmission scenarios.

Data format: programmable configuration of data bits (5/6/7/8), stop bits (1/1.5/2), and parity bits (none / odd / even), default 8N1, compatible with all standard asynchronous communication protocols.

Electrical characteristics and transmission distance: RS-232C transmission distance 15 meters; RS-422A/RS-485 differential level, high common-mode suppression ratio, strong anti-interference ability, the farthest transmission distance 1200 meters (low baud rate); TTL level compatible with short-distance communication within the board.

Multi-node networking: RS-485 mode supports 1 master multiple slaves (up to 32 nodes) bus networking, compatible with cascading of distributed measurement and control system devices.

Modem control: each channel provides complete hardware handshake signals, supports standard Modem connection and hardware flow control, ensuring stable data transmission.

Electrical isolation: each serial port has 500V optical isolation between the system bus and the serial port, completely blocking ground potential difference and common-mode interference, compatible with strong electrical interference industrial sites.

3. On-board intelligent I/O core (68000 CPU) Integrate a 10 MHz 68000 processor with XYCOM's exclusive intelligent I/O core, equipped with custom firmware, autonomously handling serial data transmission and reception, cache management, protocol verification, error handling, and interrupt response, without the intervention of the main CPU, significantly reducing the host load and enhancing system real-time performance. Built-in Terminal Driver Expansion (TDE) provides flexible user-configurable intelligent line editing functions, supporting local editing, echo control, buffer management, and is suitable for terminal and interactive device communication scenarios.

4. Flexible Interrupt and Data Transmission Control

Supports multiple event interrupts, including data reception/ transmission completion, reception errors (parity / frame / overflow), Modem signal status changes, etc. Can shield any channel interrupt, interrupt vectors can be configured, suitable for high real-time data transmission scenarios. Each channel has independent transmission and reception buffers, supports single-character or full-record transmission, supports query or interrupt-based transmission, meeting the requirements of different system architectures.

5. Industrial-grade High Reliability Design

Standard operating temperature 0℃～+55℃, suitable for industrial sites, test equipment, etc. harsh environments; the circuit board adopts multi-layer board wiring, gold finger design with gold plating, key circuits add noise suppression, strong anti-static and anti-interference ability, stable long-term operation. The front baffle is equipped with status indicator lights, facilitating rapid troubleshooting of module operation and channel communication status in the field.

III. Hardware Specifications Details

Bus Interface Specifications

Bus Protocol: IEEE 1014 VMEbus, intelligent slave device mode;

Address Space: A16/A24, short address 0x03800–0x038FF, jumper configuration base address;

Data Width: D08/D16;

Interrupt Support: VME standard interrupt, configurable priority and vector;

Backplane Interface: P1/P2 connectors;

Size: 6U (233.4mm×160mm), single slot;

Weight: Approximately 0.85kg.

Serial Channel Specifications

Channel Quantity: 8 independent isolated programmable RS-232C/RS-422A/RS-485/TTL interfaces;

Communication Controller: Special asynchronous serial controller;

Processor: 10 MHz 68000 CPU, intelligent I/O core;

Baud Rate: 300 bps–3 Mbps programmable, default 9600 bps;

Data Format: 5/6/7/8 data bits, 1/1.5/2 stop bits, no / odd / even parity;

Electrical Standard: RS-232C (±12V)/RS-422A/RS-485 (differential)/TTL;

Isolation Level: 500V光电 isolation per channel；

Transmission Distance： RS-232C maximum 15 meters， RS-422A/RS-485 maximum 1200 meters；

Networking Capability： RS-485 supports 1 master 32 slaves multi-node bus；

Connector： High-density DB or pin socket interface (depending on version).

Electrical and Environmental Specifications

Power Supply： +5V DC (VME bus power supply)， typical power consumption approximately 2.2W；

Operating Temperature： 0℃～+55℃；

Storage Temperature： -40℃～+85℃；

Humidity： 5%–95% RH (non-condensation)；

Vibration Resistance： Complies with industrial standards， suitable for equipment vibration environments.

IV. Typical Application Scenarios

1. Centralized access of multiple serial port devices in strong interference environments Suitable for scenarios with strong electromagnetic interference such as factory workshops, power and energy, and rail transportation, it can centrally connect 8 serial port devices (such as operation terminals, printers, PLCs, instruments, and frequency converters), and each module can achieve isolated access for multiple devices, completely solving the ground loop interference problem, simplifying the system architecture, and reducing slot occupation.

2. Long-distance Distributed Measurement and Control System

Used in long-distance scenarios such as factory workshops, energy equipment, and rail transportation, it is connected through the RS-485 bus, and accesses remote sensors, I/O modules, and actuators. The dual design of differential anti-interference and electrical isolation ensures stable communication in strong electromagnetic environments. The onboard CPU autonomously processes data, improving system response speed.

3. Isolation-type Upgrade of Old VME Systems with Multiple Serial Ports

Directly replace non-isolated serial port modules in the old system without modifying the chassis architecture and main program. It can be expanded to 8 isolated programmable serial ports, supporting RS-232C / differential / TTL multi-interface adaptation. It is suitable for the maintenance of old VME devices in fields such as military, aerospace, and industrial control, extending the equipment lifespan.

4. High-speed Data Acquisition and Instrument Interconnection

Used for industrial testing equipment and data recorders, connecting high-speed serial port instruments, encoders, and data collectors. The maximum baud rate of 3 Mbps meets the requirements for high-speed data transmission. The differential signal + electrical isolation ensures the integrity of long-distance transmitted data. The intelligent core autonomously manages data cache, reducing the pressure on the host.

5. Communication between Terminals and Interactive Devices

Used for intelligent buildings and security systems, connecting terminals, consoles, and Modems. Utilizing the built-in TDE intelligent line editing function, it supports local editing and echo control, adapting to interactive communication scenarios, and enhancing operational convenience.

V. Installation and Programming Key Points Installation steps

Preparations: Ensure that the P1/P2 slots of the VME chassis are intact and the +5V power supply is stable; prepare corresponding cables according to the interface type of the equipment (RS-232C ordinary shielded cable, RS-422A/RS-485 twisted shielded cable, TTL flat cable).

Jumper configuration: Set the A16/A24 base address jumper to avoid address conflicts; configure the interrupt priority and vector jumper (if interrupts are needed); set the hardware mode jumper (RS-232C/RS-422A/RS-485/TTL) according to the channel interface requirements.

Module insertion: Align the XVME-428/2 with the 6U slot and push it in smoothly to ensure that the gold fingers make good contact with the backplane, and tighten the panel fixing screws.

Cable connection: Connect the TX of the RS-232C device to RX, RX to TX, and ground; connect the A line of the RS-422A/RS-485 device to A line, B line to B line, and ground; connect the corresponding level pins of the TTL device; single-ended ground the shield layer, and keep it away from strong interference equipment such as frequency converters and motors.

Power-on self-test: After powering on the chassis, the POWER and RUN indicator lights are always on, indicating that the module is running normally; the corresponding TX/RX indicator lights flash when the channel is transmitting/receiving data.

Programming flow (simplified)

Address mapping: Configure the A16/A24 base address, map the module control, data, status, and interrupt registers to the system memory, and establish the CPU and module communication channel.

Channel mode configuration: Write the configuration word to the mode control register to set the interface type, baud rate, data format, and flow control mode for each channel.

Intelligent core configuration: Configure the TDE row editing function, buffer size, interrupt trigger condition through the command register, and enable the onboard firmware to handle serial port transactions autonomously.

Data transmission: Send/receive data through the data register, support single-character or full-record transmission; read the status register to obtain the channel status (transmitting empty, receiving full, error flag), and support query or interrupt-based transmission.

Interrupt configuration: Enable interrupts and set the trigger conditions, write the interrupt service program to handle real-time data and fault alarms, and the onboard core automatically responds to interrupts, without frequent intervention from the host.

Reset operation: When the system/software resets, the module clears the transmission/reception cache, turns off interrupts, and clears flags to ensure communication security.

Six. Core advantages

1. 8 isolated serial ports, high-density strong anti-interference integration

Single 6U slot integrates 8 isolated programmable serial ports, with a large number and high density of channels, a single module can replace multiple non-isolated serial port cards, 500V isolation completely blocks the ground loop interference, suitable for strong electrical interference industrial sites, saving chassis slots and hardware costs.

2. Four interfaces compatibility, extremely strong adaptability

Each channel supports RS-232C/RS-422A/RS-485/TTL modes, software programmable switching, no need to replace the module to adapt to different interface devices, solving the pain point of inconsistent interface of on-site equipment, significantly improving system flexibility.

3. Onboard CPU relief, high real-time performance

Equipped with a 10 MHz 68000 processor and intelligent firmware, autonomously handle serial port transmission/reception, cache and protocol verification, completely liberating the main CPU, improving the overall real-time performance and response speed of the system, suitable for high-load multi-task scenarios.

4. High baud rate + long-distance anti-interference, comprehensive performance

The highest 3 Mbps baud rate meets the requirements for high-speed data transmission. RS-422A/RS-485 differential design + 500V electrical isolation, maximum transmission distance of 1200 meters, high common-mode suppression ratio, suitable for industrial strong interference environments, balancing speed, distance and stability.

5. Industrial-grade reliability + intelligent editing, highly user-friendly

Wide temperature design from -10℃ to +55℃, anti-interference and anti-vibration, suitable for industrial harsh environments; built-in TDE intelligent line editing function, simplifies terminal interaction operations, reduces programming complexity, and enhances device usability.

6. Standard VME bus, easy integration and upgrade

Fully compatible with VMEbus specifications, directly compatible with existing 6U VME systems; simple configuration, convenient wiring, can directly replace old non-isolated single-channel serial port modules, supports upgrading of old systems and building of new systems, with strong compatibility.

VII. Notes

The module has been discontinued. When purchasing, prefer to choose second-hand / refurbished spare parts with complete test reports. Verify the model and version to avoid faulty or incompatible modules.

A single channel can only be set to one electrical mode. It is strictly prohibited to connect differential signals in RS-232C mode or RS-232C signals in differential mode. Otherwise, the interface circuit will be burned out. The ends of the RS-485 bus need to be connected with 120Ω terminal resistors to reduce signal reflection.

The power supply is +5V bus power supply to ensure voltage stability and avoid voltage fluctuations causing communication abnormalities; do not reverse the power supply connection to prevent module damage.

The wiring of the on-site strong and weak electrical separation is required. The shield layer is single-ended grounded, away from strong interference equipment, reducing the impact of electromagnetic interference on the signal, and avoiding data transmission errors.

The working temperature is 0℃ to +55℃. When installing, ensure good ventilation of the chassis to avoid overheating; in high-temperature or high-frequency communication scenarios, appropriately reduce the baud rate to extend the module lifespan.

During installation and maintenance, take precautions against static electricity, wear an anti-static wristband, operate on an anti-static workbench; before plugging or unplugging the module, cut off the power supply of the chassis to prevent damage to the backplane and module due to live plugging or unplugging.

The onboard 68000 processor firmware is a dedicated program. It is prohibited to modify or rewrite it at will, otherwise it may cause module functional abnormalities or inoperability.