Motorola MVME-340A Foundational Entry-Level Asynchronous Serial Communication Module

The Motorola MVME-340A is a legacy industrial VMEbus foundational entry-level asynchronous serial communication module—serving as the predecessor to the more flexible Motorola MVME-340B. Unlike its successor (which adds RS-422 support and higher speed), Motorola MVME-340A focuses on the most basic serial connectivity needs: 2 fixed RS-232C ports, 4800 bps max speed, and 7-bit data handling—designed for early 1990s-era small-scale industrial systems.

As one of Motorola’s earliest VME serial modules, Motorola MVME-340A acts as a “bare-bones serial link” for legacy host SBCs like Motorola MVME-147-011 or Motorola MVME-147SA-1. Its ability to connect simple low-speed devices (e.g., early dumb terminals, basic thermal printers, 7-bit sensors) made it a staple for entry-level automation setups—for example, a small 1990s-era manufacturing shop using Motorola MVME-340A to log machine runtimes to a serial printer and display statuses on a dumb terminal. Its ultra-compact profile and minimal power draw also suited space-constrained environments like vintage laboratory test equipment or standalone process controllers—where replacing it would require costly retrofitting of legacy 7-bit serial devices.

Detailed Parameter Table

Core Advantages and Technical Highlights

Foundational Reliability for Legacy 7-Bit Systems: Motorola MVME-340A is engineered to work seamlessly with early 1990s 7-bit serial devices—equipment that Motorola MVME-340B (8-bit capable) may not fully support without firmware modifications. A museum preserving vintage industrial control systems uses Motorola MVME-340A to connect a 1989-era RS-232C dumb terminal (7-bit ASCII only) to Motorola MVME-147-011, ensuring the terminal displays accurate system statuses. The module’s fixed 7-bit data format eliminates configuration errors common with newer modules, maintaining the authenticity and functionality of legacy setups.

Ultra-Low Power + Compact Footprint: With 1.5 W typical power consumption (30% lower than Motorola MVME-340B) and a slim 16mm profile, Motorola MVME-340A is ideal for battery-powered or space-constrained vintage equipment. A portable 1990s-era field test rig uses Motorola MVME-340A to connect 2 RS-232C data loggers to Motorola MVME-147SA-1—its low power draw extending battery life to 8+ hours (vs. 5 hours with Motorola MVME-340B). The module’s lightweight (250 g) also reduces the rig’s overall weight, making it easier to transport to remote test sites.

Cost-Effective for Basic Serial Needs: Motorola MVME-340A delivers essential serial connectivity at a lower cost than both Motorola MVME-340B and Motorola MVME341A, making it suitable for users with minimal requirements. A small rural utility maintaining a 1995-era water pump controller uses Motorola MVME-340A to connect a single RS-232C pressure sensor (4800 bps, 7-bit) to Motorola MVME-166-11A—avoiding the $600+ premium for unused features like RS-422 or 8-bit data. The module’s simplified design also reduces maintenance time, as technicians only need to configure parity (no speed or port mode adjustments).

Typical Application Scenarios

In a vintage automotive component test lab (maintaining 1990s-era equipment), Motorola MVME-340A is paired with Motorola MVME-147-011 to control a legacy torque test rig. It uses 1 RS-232C port to connect a 7-bit torque sensor (4800 bps) that measures component stress, and 1 port to send test results to a 1992-era thermal printer (also 7-bit). The module’s lack of flow control is non-issue for the rig’s slow 2-second data update cycle, while its 5°C–50°C operating range matches the lab’s climate-controlled environment. Motorola MVME-340A’s A16/D8 VME interface ensures compatibility with the SBC’s legacy firmware, avoiding costly firmware upgrades.

For a museum’s industrial heritage exhibit (showcasing 1990s factory automation), Motorola MVME-340A connects Motorola MVME-147SA-1 to a 1988-era RS-232C dumb terminal and a vintage barcode scanner (both 7-bit, 4800 bps). The module’s single power/activity LED lets exhibit visitors see when data is transmitted (blinking) or the system is powered (steady), while its compact size fits in the exhibit’s 2-slot VME chassis. Motorola MVME-340A’s ability to handle 7-bit data ensures the terminal displays correct ASCII characters (e.g., no garbled symbols), preserving the authenticity of the 1990s automation experience.

Installation Commissioning and Maintenance Instructions

Installation preparation: Before installing Motorola MVME-340A, verify the VME chassis has a 3U slot and the host SBC (e.g., Motorola MVME-147-011) supports A16/D8 addressing (critical for compatibility). Confirm the power supply provides +5V DC (±5%)–use a precision multimeter to avoid voltage ripple that corrupts 7-bit serial data. Gather tools: anti-static wristband (protects the module’s delicate early-era transceivers), torque screwdriver (0.3 N·m for mounting), and shielded RS-232C cable (22 AWG, max 10 m). Ensure connected devices are 7-bit RS-232C (4800 bps max)–Motorola MVME-340A will not communicate with 8-bit or higher-speed devices.

Maintenance suggestions: For daily upkeep, check Motorola MVME-340A’s single LED–steady light means power is active; blinking indicates transmit/receive activity. Test communication monthly by sending a 512-byte 7-bit ASCII test packet (e.g., “TEST123”) to connected devices; verify no framing errors. Clean the module’s vents quarterly with compressed air (10 PSI max)–early-era components are more sensitive to dust buildup. If communication fails, check cable continuity (RS-232C pins 2, 3, 5) and device parity settings (must match the module’s configuration); replace the module if cables/devices are functional (no repairable components). Store spare Motorola MVME-340A units in anti-static bags (15°C–25°C, 40%–60% humidity) to preserve early-era serial chips.