Description
The AVME VME-SSI is a specialized VMEbus-compatible interface module designed to acquire high-resolution position data from Synchronous Serial Interface (SSI) encoders commonly used in precision motion control applications. Developed by AVME (also referenced as AVMESSI in legacy documentation), the AVME VME-SSI serves as a robust bridge between industrial absolute encoders—such as those from Heidenhain, Baumer, or Sick—and real-time VME-based control systems found in test stands, CNC machinery, robotics, and scientific instrumentation.
As a single-slot 6U VME module, the AVME VME-SSI supports multiple independent SSI channels (typically 2 or 4, depending on configuration), each capable of reading 24-bit absolute position values at high clock rates (up to 1 MHz). The module features optically isolated inputs to protect against ground loops and electrical noise, ensuring signal integrity in electrically harsh environments. Its integration into VME systems enables deterministic data acquisition synchronized with other control tasks—making the AVME VME-SSI indispensable for applications demanding micron-level positioning accuracy and sub-millisecond response times.
VME-SSI AVMESSI
Technical Specifications
| Parameter Name | Parameter Value |
| Product Model | VME-SSI |
| Manufacturer | AVME (AVMESSI) |
| Product Type | SSI Encoder Interface Module for VMEbus |
| Bus Standard | VME64 / VMEbus (IEEE 1014), 6U form factor |
| Number of SSI Channels | 2 or 4 (model-dependent) |
| Encoder Compatibility | Absolute rotary/linear encoders with SSI output (RS-422 compliant) |
| Data Resolution | Up to 24 bits per channel |
| Clock Frequency | Adjustable up to 1 MHz |
| Input Isolation | Opto-isolated (2.5 kV typical) |
| Power Requirements | +5V, +12V, –12V from VME backplane (typical: 1.5A @ +5V) |
| Operating Temperature | 0°C to +60°C (commercial grade); extended options available |
| Dimensions | 6U VME: 233 mm × 160 mm (H × D) |
| Mounting | Standard VME card cage with DIN 41612 connector |
Main Features and Advantages
High-channel-density SSI acquisition:
The AVME VME-SSI supports multiple encoder channels in a single VME slot, reducing system footprint and cost compared to discrete solutions. Each channel operates independently with programmable clock polarity and timing, accommodating a wide range of encoder vendors and protocols.
Industrial-grade noise immunity:
With full optical isolation on all SSI lines, the AVME VME-SSI rejects common-mode noise from motors, drives, and switching power supplies—critical in environments like dynamometer test cells or robotic welding stations where signal corruption could cause catastrophic positioning errors.
Real-time deterministic performance:
Integrated directly into the VMEbus architecture, the AVME VME-SSI delivers encoder data with microsecond-level latency, enabling tight servo-loop closure in high-dynamic applications such as flight simulators or wafer steppers. Data can be read via memory-mapped I/O or interrupt-driven DMA for minimal CPU overhead.
Flexible configuration and diagnostics:
The module includes onboard status registers and error flags (e.g., timeout, parity mismatch) accessible via software. Users can adjust clock frequency, data length, and idle time through register writes—allowing adaptation to both standard and proprietary SSI implementations without hardware changes.
Long-term availability for legacy systems:
Though AVME/AVMESSI is no longer actively manufacturing new units, the AVME VME-SSI remains in demand for maintaining decades-old VME systems in defense, aerospace, and research. Reconditioned and tested units ensure continued operation where migration is impractical or cost-prohibitive.
Application Field
The AVME VME-SSI is extensively used in high-precision industrial and scientific systems that rely on VME-based real-time computing. In aerospace test facilities, it reads position feedback from load frames and actuator-mounted encoders during structural fatigue testing—where data integrity directly impacts certification validity. Semiconductor equipment manufacturers integrate the AVME VME-SSI into wafer alignment and inspection stages, leveraging its 24-bit resolution to achieve nanometer-scale repeatability.
In automotive R&D, engine dynamometers use the AVME VME-SSI to track crankshaft and camshaft angles with micro-degree accuracy, synchronizing combustion analysis across hundreds of test cycles. Similarly, particle physics laboratories employ the AVME VME-SSI in beamline positioning systems, where thermal drift compensation requires ultra-stable encoder interfacing over long cable runs. Even in legacy CNC retrofits, the AVME VME-SSI enables modern motion controllers to reuse existing high-end absolute encoders—preserving capital investment while upgrading control logic. Across these domains, the AVME VME-SSI exemplifies the enduring value of purpose-built industrial I/O hardware.
VME-SSI AVMESSI
Related Products
- VME-DIO: General-purpose digital I/O module from AVME, often used alongsideVME-SSI for limit switches or enable signals
- VME-QUAD: Quadrature encoder interface module—complementsVME-SSI in hybrid incremental/absolute systems
- VMIC VMIVME-7750: High-performance VME CPU board commonly paired withVME-SSI in real-time control racks
- Heidenhain ERN 180: Popular rotary encoder with SSI output, fully compatible withVME-SSI
- SBS GCS-4: Alternative SSI interface for VME from SBS Technologies—functional competitor toVME-SSI
- VME-PWR: AVME power supply module for standalone VME crates housingVME-SSI cards
- Baumer HOG 10: Heavy-duty absolute encoder frequently interfaced viaVME-SSI in steel mill applications
- DSP6000: AVME DSP co-processor module that can offload position interpolation from the main CPU when used withVME-SSI
