GE SST-PFB3-VME2 Profibus Interface Card – SST Series

GE SST-PFB3-VME2 Profibus DP/FMS VME Interface Card – Fieldbus Master/Slave for VME64 Architectures

The SST-PFB3-VME2 is a single-slot, 6U VME bus interface card manufactured by GE (General Electric) under the SST (Smart Serial Technology) product line. It provides a dedicated PROFIBUS DP and PROFIBUS FMS communication channel for VME64/VME32 backplane systems, enabling deterministic fieldbus integration in process control, power generation, and factory automation environments. The card operates as both a Class 1 DP master and a DP slave, making it suitable for hierarchical network topologies where a VME-hosted controller must simultaneously manage field devices and report upstream to a supervisory system.

In a typical control loop, the SST-PFB3-VME2 sits between the VME-based real-time processor and the PROFIBUS field segment. The onboard microcontroller handles all PROFIBUS token-passing and timing autonomously, offloading the host CPU from protocol stack execution. This architecture ensures that PROFIBUS cycle times remain deterministic regardless of host CPU load — a critical requirement in closed-loop control applications where jitter in I/O refresh directly affects PID stability and process safety margins.

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Technical Parameters

Hardware Logical Analysis

The SST-PFB3-VME2 implements a dual-port SRAM (DPRAM) architecture as the primary host-to-card communication mechanism. The VME host processor accesses a shared memory window mapped into the VME address space (A24/D16 or A32/D32 selectable via onboard DIP switches), while the card’s embedded microcontroller independently manages the PROFIBUS physical layer and data link layer (FDL). This strict separation of the host application layer from the fieldbus protocol stack eliminates protocol-induced latency from the host CPU’s execution timeline.

EMC and Signal Integrity: The card’s PROFIBUS transceiver section is galvanically isolated from the VME backplane power domain. Opto-coupler isolation on the RS-485 differential pair provides a minimum 500 V isolation barrier, suppressing common-mode transients that are common in industrial environments with long cable runs or mixed-voltage field panels. The RS-485 driver complies with IEC 61158-2 electrical specifications, supporting cable lengths up to 1,200 m at 93.75 kbit/s without repeaters.

Token-Ring Arbitration: PROFIBUS DP uses a token-passing bus access method among masters. The SST-PFB3-VME2’s onboard FDL controller manages token rotation autonomously, maintaining the target token rotation time (TTR) independent of host CPU scheduling. This is particularly significant in multi-master configurations where token loss or excessive GAP update cycles can degrade network throughput. The card’s firmware implements the full FDL state machine, including GAP maintenance, live-list management, and retry handling per IEC 61158-3.

Watchdog and Fault Detection: An independent hardware watchdog monitors the onboard microcontroller. If the protocol processor fails to reset the watchdog within the configured interval, the card asserts a VME SYSFAIL* signal and drives all DP slave outputs to their configured fail-safe states. This behavior is configurable per slave via the GSD (General Station Description) parameter set loaded during initialization.

Configuration and Diagnostics: The card exposes a structured mailbox interface in DPRAM for host-initiated commands: start/stop data exchange, read slave diagnostics (standard and extended), set slave parameters, and retrieve bus statistics (frame error count, retry count, token loss events). These counters are accessible without interrupting the active data exchange cycle, enabling non-intrusive runtime diagnostics.

System Integration Benefits

• Protocol Stack Offload: The embedded microcontroller executes the complete PROFIBUS FDL and DP application layer, freeing the VME host CPU for real-time control algorithms without fieldbus scheduling overhead.
• Deterministic I/O Refresh: With baud rates up to 12 Mbit/s and autonomous token management, the card delivers consistent DP cycle times below 1 ms for small slave counts, supporting tight PID loop execution on the host processor.
• Dual-Protocol Flexibility: Simultaneous DP and FMS support on a single card eliminates the need for separate interface hardware in mixed-protocol installations, reducing rack space and inter-card wiring complexity.
• Non-Intrusive Diagnostics: Runtime access to slave diagnostic data and bus statistics via DPRAM mailbox allows maintenance personnel to assess network health without halting the control process — a key requirement for continuous-process industries.
• Scalable Node Density: Support for up to 125 slave nodes per channel accommodates large distributed I/O architectures typical of power plant auxiliary systems, water treatment facilities, and automotive body-shop lines.
• Legacy VME Compatibility: VME32 backward compatibility allows the card to be deployed in existing VME32 chassis without hardware modification, protecting capital investment in legacy control platforms.
• Configurable Interrupt Mapping: VME interrupt levels 1–7 are software-selectable, allowing the card to coexist with other VME peripherals without IRQ conflicts in multi-board systems.
• Fail-Safe Output Behavior: Hardware watchdog-triggered fail-safe state propagation to DP slaves ensures process safety compliance in applications governed by IEC 61511 or IEC 62061 functional safety standards.
• ESD and Transient Protection: Opto-isolated RS-485 interface with TVS diode protection on the PROFIBUS connector suppresses cable-induced transients up to ±15 kV (IEC 61000-4-2 contact discharge), extending card service life in electrically noisy environments.
• Structured GSD-Based Configuration: Full GSD file support enables integration with standard PROFIBUS configuration tools (e.g., Siemens STEP 7 HW Config, Softing PB-Config), reducing commissioning time and configuration errors.

Quality Assurance & Global Logistics

Every SST-PFB3-VME2 unit supplied by siemensplc.com is sourced through verified industrial distribution channels with full traceability to the original GE manufacturing batch. Physical inspection covers PCB layer integrity, connector pin condition, date code authenticity, and label verification against OEM documentation. Where applicable, functional bench testing confirms PROFIBUS communication establishment and VME bus enumeration prior to dispatch.

Units are packed in anti-static ESD shielding bags, placed in foam-lined cartons rated for international air freight handling. Shipments originate from our warehouse in Xiamen, China, with typical dispatch within 1–3 business days for in-stock items. We ship via DHL Express, FedEx International Priority, and UPS Worldwide Expedited — all with door-to-door tracking and commercial invoice documentation for customs clearance. Export classification and HS code documentation are provided on request for import duty pre-calculation.

All units carry a 12-month warranty from the date of shipment. Warranty coverage includes functional failure under normal operating conditions. Advance replacement is available for qualified accounts. Bulk and blanket purchase orders are accommodated with scheduled delivery agreements.

Contact Information

Email: [email protected]
WhatsApp: +86 18359268345
Web: siemensplc.com
Location: Xiamen, China
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