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3. Key Technical Specifications
| Parameter | Value |
|---|---|
| Number of Axes / Drives, Max | 16 |
| SERCOS Data Rate | 4 Mbps or 8 Mbps |
| SERCOS Cycle Time @ 4 Mbps | 0.5 ms (up to 2 drives), 1 ms (up to 4), 2 ms (up to 8) |
| SERCOS Cycle Time @ 8 Mbps | 0.5 ms (up to 4 drives), 1 ms (up to 8), 2 ms (up to 16) |
| Drive Control Modes | Position, Velocity, Torque |
| Backplane Current @ 5.1 V DC | 760 mA |
| Backplane Current @ 24 V DC | 2.5 mA |
| Power Dissipation | 5.0 W |
| Media | Plastic fiber-optic SERCOS ring |
| Slot Width | 1 |
| Compatible Chassis | 1756-A4, A7, A10, A13, A17 |
| Operating Temperature | 0 °C to +60 °C |
4. Product Introduction
The Allen-Bradley 1756-M16SE is a single-slot SERCOS interface module for ControlLogix systems. It provides a fiber-optic real-time communication link between a ControlLogix controller and up to 16 SERCOS-compatible servo drives.
Supported data rates are 4 Mbps and 8 Mbps, with cycle times of 0.5 ms, 1 ms, or 2 ms depending on the number of axes and selected baud rate. The module supports position, velocity, and torque control modes and is commonly used with Kinetix 2000, 6000, 6200, 7000, and Ultra3000 SERCOS drives. SERCOS is a mature technology; new designs typically migrate to CIP Motion over EtherNet/IP.
5. Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to this Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| OK or LINK LED steady red | Module fault or SERCOS ring break | ✅ High | Check fiber connections and ring continuity | Inspect/replace fiber cables; verify terminations |
| No communication with drives | Incorrect baud rate or cycle time | ✅ High | Verify SERCOS configuration matches drive settings | Match data rate and cycle time in Studio 5000 |
| Axes not responding | Drive offline or phase error | ✅ High | Check drive status and SERCOS phase LEDs | Power-cycle drives; re-establish ring |
| Module OK LED off / faulted | Backplane power or seating issue | ❌ Medium | Verify chassis power and module seating | Reseat module; check power supply capacity |
| Intermittent motion faults | Fiber contamination or excessive length | ✅ Medium | Clean fiber ends; check total ring length | Clean connectors; stay within fiber length limits |
| High backplane current | Chassis overload | ❌ Low | Measure total chassis current draw | Redistribute modules or upgrade power supply |
If diagnostics remain unclear, capture LED status, SERCOS ring diagnostics, and drive fault codes before contacting support.
1756-M16SE
1756-M16SE
6. Frequently Asked Questions (FAQ)
Q: Is the 1756-M16SE still in production? The SERCOS motion modules are mature. New units may still be available through distribution, but Rockwell’s current motion focus is CIP Motion on EtherNet/IP. Confirm availability before ordering.
Q: How many axes can one 1756-M16SE control? Up to 16 SERCOS drives/axes per module. A single ControlLogix controller can support multiple modules (system limit typically 32 axes depending on controller and configuration).
Q: What fiber-optic cable is required? Plastic fiber-optic cables such as 2090-SCEP (non-jacketed), 2090-SCVP (PVC jacket), or 2090-SCNP (nylon jacket). Maintain proper bend radius and cleanliness.
Q: What is the difference between 1756-M08SE and 1756-M16SE? The M08SE supports up to 8 axes; the M16SE supports up to 16 axes. Both use the same 4/8 Mbps SERCOS rates and control modes.
Q: Can the module be used with modern Kinetix drives? It is compatible with older SERCOS Kinetix drives (2000/6000/6200/7000 series and Ultra3000). Newer Kinetix drives that use only CIP Motion over EtherNet/IP require different interface modules or embedded Ethernet.
Q: Does the module support hot-swapping? Yes. ControlLogix supports Removal and Insertion Under Power (RIUP) when the system is properly configured. Follow Rockwell safety guidelines.
Q: Why is New Surplus sometimes priced lower? These are genuine Allen-Bradley modules from excess inventory or cancelled projects. They are unused and typically supplied with anti-static protection. They are not refurbished unless specifically stated.
