Product Overview

The 1756-SYNCH is a high-performance SynchLink communication interface developed by Allen-Bradley for the ControlLogix platform. This module is engineered to provide deterministic, microsecond-level time synchronization across multiple chassis, making it a cornerstone for complex motion control and multi-axis drive coordination. By utilizing a dedicated fiber-optic link, the 1756-SYNCH enables various controllers to broadcast axis data and align Coordinated System Time (CST) clocks with extreme precision, bypassing the latency often associated with standard industrial networks.

This module is specifically designed for high-speed industrial applications where electrical noise immunity is paramount. The fiber-optic medium ensures that timing signals remain untainted by electromagnetic interference (EMI) or ground loops, allowing for reliable master/follower synchronization over distances up to 300 meters. It is an essential component for maintaining the phase alignment of distributed drives in high-dynamic environments such as paper conversion, web handling, and precision printing.

Deterministic Performance and Architecture

The 1756-SYNCH operates with a fixed 5 Mbps throughput, delivering a rapid 50 μs frame speed that ensures real-time data delivery. Each 30-byte data frame is optimized for efficiency, containing 24 bytes of user data secured by a 2-byte CRC for rigorous error detection. This architecture allows a "master" controller to broadcast position and velocity references to all nodes on the SynchLink network simultaneously, eliminating the "controller skew" that can occur in high-speed machinery.

While the module is primarily installed in a standard ControlLogix 1756 chassis, it supports versatile network topologies—including star and daisy-chain configurations—when integrated with external SynchLink hubs or bypass switches. Despite its legacy status, the 1756-SYNCH remains a critical spare for facilities relying on ultra-fast, chassis-to-chassis clock distribution and motion synchronization.

Technical Specifications

• Module Type: SynchLink Fiber Optic Communication Interface

• Controller Platform: Allen-Bradley ControlLogix (1756)

• Part Number: 1756-SYNCH

• Transmission Medium: Dual Fiber-Optic Ports (200/230 micron HCS)

• Data Transfer Rate: 5 Mbps (Fixed)

• Link Performance: 50 μs Frame Speed

• Max Distance: Up to 300 Meters (984 feet)

• Backplane Current Draw: 1200 mA @ 5.1V DC; 3 mA @ 24V DC

• Thermal Dissipation: 6.2 Watts (21.2 BTU/hr)

• Operating Temperature: 0°C to 60°C (32°F to 140°F)

• Vibration/Shock Resistance: 30g Functional Shock

• Physical Dimensions: 3.6 x 13 x 14 cm

• Weight: 0.3 kg (0.66 lbs)

High-Speed Motion Applications

• Web Handling: Synchronizing tension and speed across multiple rollers in continuous material processing.

• Paper and Pulp Mills: Coordinating large drive sections to prevent web breaks and maintain product consistency.

• Converting Lines: Providing the microsecond timing required for high-speed cutting and placement.

• Multi-Chassis Sync: Aligning system clocks across separate ControlLogix racks for integrated plant-wide control.