Allen-Bradley 1756-M08SE ControlLogix 8-Axis SERCOS Interface Module

Product Overview

The Allen-Bradley 1756-M08SE is a high-performance motion control module designed for the ControlLogix® platform, serving as a dedicated interface between the programmable automation controller and SERCOS (Serial Real-time Communications System) digital drives. This module enables the synchronized control of up to eight axes of motion, providing a seamless fiber-optic link to Kinetix® and Ultra™ series servo drives. By utilizing light-based signal transmission, the 1756-M08SE ensures total immunity to electromagnetic interference (EMI) and electrical noise, which is critical for maintaining signal integrity in high-voltage industrial environments.

This module is an essential component for complex motion applications such as multi-axis packaging, material handling, and robotic assembly lines. It allows the Logix5000™ processor to execute motion instructions—including position, velocity, and torque loops—and transmit them to the drives with sub-millisecond determinism. The 1756-M08SE simplifies system architecture by eliminating the need for extensive copper wiring, replacing it with a high-speed fiber-optic ring.

Real-Time Performance and Synchronization

The 1756-M08SE operates at selectable data rates of 4 Mbps or 8 Mbps, allowing engineers to balance the number of connected nodes with required loop update times. The module supports a highly deterministic communication cycle, ensuring that all eight axes receive their position command simultaneously. This precise synchronization is vital for applications involving electronic gearing, camming, or coordinated linear and circular interpolation.

• Cycle Time at 4 Mbps: 0.5 ms (2 axes), 1.0 ms (4 axes), 2.0 ms (8 axes).

• Cycle Time at 8 Mbps: 0.5 ms (4 axes), 1.0 ms (8 axes).

The module is fully compatible with standard 1756 ControlLogix chassis (A4, A7, A10, A13, and A17 models) and interfaces directly with the backplane to exchange motion data with the controller. It supports the use of 2090-series plastic (POF) or glass (HCS) fiber-optic cables, providing flexibility for different cable run lengths and durability requirements.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Number: 1756-M08SE

• Module Type: SERCOS Interface Servo Module

• Number of Axes: 8 Maximum

• Communication Rate: 4 Mbps or 8 Mbps (Selectable)

• Backplane Current (5.1V DC): 760 mA

• Backplane Current (24V DC): 2.5 mA

• Power Dissipation: 4.0 Watts

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

• Fiber Optic Connectors: FSMA type

• Drive Compatibility: Kinetix 2000, 6000, 6200, 7000, and Ultra3000 SERCOS

• Weight: 0.22 kg

• Dimensions: 3.5 x 14.0 x 14.5 cm

Hardware and Software Integration

• Software Support: Configuration and programming are managed via Studio 5000 Logix Designer® or RSLogix™ 5000, utilizing integrated Motion-on-SERCOS instructions.

• Diagnostic Features: Onboard LEDs provide real-time status of the SERCOS ring (Ring Status, Module Status, and Link status).

• Non-Volatile Storage: System parameters and drive configurations are stored within the controller and downloaded to the 1756-M08SE upon power-up, simplifying module replacement.

• Ruggedized Build: Tested for 30 g operational shock and industrial vibration, ensuring durability in continuous-duty manufacturing settings.