Allen-Bradley 1756-ENET ControlLogix Ethernet Communication Module

Configured for high-speed data transmission in ControlLogix industrial networks, the Allen-Bradley 1756-ENET (1756-ENET Ethernet Communication Module) provides direct physical execution of messaging and I/O scanning functions. This module utilizes a 10 Mbps Ethernet port and an AUI port to facilitate communication between the ControlLogix backplane and external Ethernet-based devices, functioning as either a scanner or adapter within linear network topologies.

Hardware Specifications

Profinet / EtherNet/IP Deterministic Networks & Firmware Flash Compatibility

The 1756-ENET operates on a cyclical polling basis, requiring tight management of network update times to maintain deterministic performance within the ControlLogix environment. Firmware flash compatibility is limited; users must verify that the module firmware is compatible with the controller revision to prevent communication timeouts or backplane bus communication velocity mismatches. In linear topologies, network traffic must be monitored to ensure the 10 Mbps bandwidth limit is not exceeded, as high-density I/O traffic can lead to packet collisions and increased jitter in message delivery.

Frequently Asked Questions

Q: Does the 1756-ENET support hot-swapping within the ControlLogix chassis?

A: Yes. The module supports Removal and Insertion Under Power (RIUP) in ControlLogix chassis. However, ensure that the communication cable is disconnected from the Ethernet or AUI port prior to unseating the module to avoid potential transient voltage spikes on the network media.

Q: Can this module be installed in any slot within the 1756-A series chassis?

A: Yes. As a communication module, the 1756-ENET can be placed in any available slot within the 1756-A4, -A7, -A10, or -A13 chassis. It does not require a specific slot location, provided the backplane power supply (e.g., 1756-PA72) has sufficient capacity to handle the 900 mA load at 5.1 VDC.

Field Installation Guidelines

• Chassis Mounting: Align the module with the guide rails of the chassis and slide it in until the backplane connector is fully seated. Tighten the top and bottom retaining screws to ensure a secure mechanical connection and proper grounding.
• Cable Termination: Use shielded twisted pair Ethernet cabling for the RJ45 port and ensure appropriate transceiver hardware is used for the AUI port. Ensure cables are routed away from high-voltage AC lines to minimize electromagnetic interference.
• Grounding: The ControlLogix chassis must be bonded to a low-impedance earth ground. The 1756-ENET relies on the chassis backplane for grounding; ensure the chassis is properly installed and grounded before powering the module.
• Environment: Although rated for 0 deg C to 60 deg C, maintain adequate clearance above and below the module to facilitate passive airflow and heat dissipation, as the unit dissipates up to 13.3 W.