SST 5136-CN-VM ControlNet Communications Module – 5136 Series

SST 5136-CN-VM: VME-Based ControlNet Interface Module for Deterministic Industrial Networks

The SST 5136-CN-VM is a single-slot, 6U VME form-factor ControlNet communications module engineered for embedded control architectures that demand deterministic, scheduled data exchange across multi-node industrial networks. Manufactured under the SST (Solid State Technology) product line — subsequently acquired by Woodhead Industries and later integrated into the Molex portfolio — this module occupies a well-defined position in legacy and hybrid automation systems where VME backplane infrastructure remains the structural backbone of the control platform.

ControlNet, as defined by IEC 61158 and the ODVA specification, operates at a fixed 5 Mbps data rate over RG-6 coaxial cable with a dual-redundant topology (Channel A / Channel B). The protocol’s time-division multiplexing architecture separates scheduled (implicit) messaging from unscheduled (explicit) messaging within each Network Update Time (NUT) interval — a property that makes it fundamentally different from Ethernet-based fieldbus variants where latency is probabilistic. The 5136-CN-VM implements the full ControlNet Media Access Control (MAC) layer in hardware, offloading the host VME processor from protocol timing overhead and enabling node participation with sub-millisecond jitter on scheduled connections.

This module is particularly relevant in process industries, automotive body-in-white lines, and utility SCADA architectures where Rockwell Automation ControlLogix or PLC-5 systems serve as the network scheduler and the VME host acts as a data concentrator, historian gateway, or supervisory computation node. The 5136-CN-VM bridges these two domains without requiring a separate gateway appliance, reducing latency, eliminating an additional failure point, and preserving the deterministic timing budget of the ControlNet segment.

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Technical Parameters

Hardware Logical Analysis

MAC Layer Hardware Offload: The 5136-CN-VM implements ControlNet’s Media Access Control entirely in dedicated silicon rather than delegating it to the host VME processor. The on-board ASIC manages the Concurrent Time Domain Multiple Access (CTDMA) algorithm — the mechanism by which each node is assigned a deterministic transmission window within each NUT cycle. This design means the host CPU is interrupted only when a complete data frame is ready in the dual-port SRAM, not for every bit-level protocol event. In a 10 ms NUT configuration with 20 scheduled connections, the host interrupt rate is bounded and predictable, which is essential for real-time OS schedulers running on the VME backplane.

Dual-Port SRAM Architecture: Data exchange between the VME host and the ControlNet ASIC occurs through a shared dual-port SRAM region mapped into the VME address space. The module’s internal arbiter manages simultaneous read/write access from both sides without bus contention. This eliminates the need for software semaphore polling loops and reduces host-side latency to a single memory-mapped register read — typically completing within one VME bus cycle (100–200 ns at 10 MHz VME clock).

EMC and Signal Integrity Design: The coaxial BNC connectors on the module’s front panel are directly coupled to the ControlNet physical layer transceiver, which implements the Manchester-encoded, 75 Ω impedance-matched signaling defined by the ODVA ControlNet specification. The PCB layout isolates the high-frequency transceiver circuitry from the VME bus logic using a ground plane partition, reducing conducted emissions and improving immunity to common-mode noise injected through the backplane. The module meets EN 55011 Class A radiated emission limits and IEC 61000-4-4 electrical fast transient (EFT) immunity at 2 kV, making it suitable for installation in panel environments adjacent to variable-frequency drives and contactor banks.

Redundant Channel Topology: The dual BNC interface supports ControlNet’s inherent media redundancy. Channel A and Channel B carry identical data streams over physically separate coaxial runs. The on-board receiver logic continuously monitors signal quality on both channels and performs automatic switchover in the event of cable fault, connector failure, or signal degradation — without host software intervention and without dropping a scheduled connection. Switchover time is within one NUT interval, preserving the deterministic timing contract of the network.

Interrupt and DMA Handling: The module supports VME interrupt levels IRQ1 through IRQ7, configurable via on-board jumpers or software registers. In high-throughput applications, the SST driver stack can be configured to use interrupt-driven notification for unscheduled (explicit) message completion while relying on polled SRAM access for scheduled data — a hybrid approach that minimizes interrupt latency for time-critical paths while keeping CPU overhead low for background messaging traffic.

System Integration Benefits

• Deterministic NUT-Aligned Data Delivery: Scheduled connections on the 5136-CN-VM are synchronized to the ControlNet NUT, configurable from 2 ms to 100 ms. This guarantees that process variable updates arrive at the VME host within a fixed, bounded window — a property that cannot be replicated with unmanaged Ethernet or DeviceNet polling architectures.
• Zero-Gateway Architecture: Embedding ControlNet connectivity directly on the VME backplane eliminates the external gateway appliance that would otherwise be required to bridge VME-hosted applications to the ControlNet segment. This removes a serial bottleneck, reduces BOM cost, and eliminates a potential single point of failure in the communication path.
• Transparent Diagnostic Access: The module exposes ControlNet network diagnostic counters — including CRC error counts, media redundancy switchover events, and node connection status — through memory-mapped registers accessible to the host application. This allows the supervisory software to log network health data alongside process data without requiring a separate network analysis tool.
• Concurrent Scheduled and Unscheduled Messaging: The CTDMA protocol allocates bandwidth for both implicit (scheduled I/O) and explicit (unscheduled messaging, parameter reads/writes) within each NUT. The 5136-CN-VM supports both simultaneously, allowing the host to perform online parameter configuration of remote devices without disrupting the real-time I/O data stream.
• Multi-OS Driver Ecosystem: SST provides validated driver packages for Windows (WDM architecture), VxWorks (BSP-integrated), QNX Neutrino, and Linux (kernel module). This breadth of OS support allows the same hardware to be reused across platform migrations without hardware replacement, protecting capital investment in the VME chassis infrastructure.
• Up to 99-Node Segment Capacity: A single 5136-CN-VM can participate in a ControlNet segment with up to 99 addressable nodes. In large distributed I/O architectures — such as a body-in-white welding line with 40+ remote I/O racks — this eliminates the need for segment bridging and the associated latency penalty of inter-segment routing.
• RSNetWorx Integration: The module is fully compatible with Rockwell Automation’s RSNetWorx for ControlNet configuration tool. Network scheduling, connection parameter configuration, and node commissioning can be performed from the same engineering workstation used to configure the ControlLogix or PLC-5 scheduler, reducing the number of software tools required in the project environment.
• Coexistence with Legacy PLC-5 and SLC Systems: ControlNet was the primary inter-controller communication medium for Rockwell’s PLC-5 and SLC 500 platforms. The 5136-CN-VM allows VME-hosted applications to exchange data with these legacy controllers without requiring a protocol conversion layer, supporting phased migration strategies where legacy PLCs remain in service alongside newer control hardware.

Quality Assurance & Global Logistics

Every SST 5136-CN-VM unit supplied by siemensplc.com is sourced through verified industrial surplus and authorized distribution channels. Prior to dispatch, each module undergoes a structured inspection protocol: visual examination of PCB, connectors, and component markings; power-on functional verification using SST diagnostic utilities; and BNC connector impedance check to confirm physical layer integrity. Units that do not pass all inspection criteria are quarantined and not offered for sale.

Counterfeit detection is applied at intake. SST 5136-series modules carry identifiable PCB revision markings, component date codes, and ASIC part numbers that are cross-referenced against known-genuine reference units. Any unit with inconsistent markings is rejected regardless of claimed provenance.

All orders ship from our warehouse in Xiamen, China. Xiamen is served by Xiamen Gaoqi International Airport (XMN) with direct cargo connections to major logistics hubs in Europe, North America, Southeast Asia, and the Middle East. Standard export documentation — commercial invoice, packing list, and certificate of origin — is prepared for every shipment. DHL Express, FedEx International Priority, and UCP air freight are available. Typical transit times: 3–5 business days to Europe and North America; 2–3 business days to Southeast Asia and Japan. Sea freight consolidation is available for multi-unit orders where lead time permits.

A 12-month warranty is provided from the date of shipment. Warranty coverage includes replacement of units that exhibit functional failure under normal operating conditions. Damage resulting from incorrect installation, overvoltage, or physical impact is excluded. Warranty claims are processed within 5 business days of receipt of the returned unit at our Xiamen facility.

Contact Information

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