Allen-Bradley 1756-ENBT/A ControlLogix EtherNet/IP Communication Module

The Allen-Bradley 1756-ENBT/A, also cataloged as the 1756-ENBT/A EtherNet/IP communication module, operates as a dedicated hardware component for Ethernet/IP protocol bridging and backplane data exchange within ControlLogix 1756 chassis networks.

Configured for IEEE 802.3 Ethernet/IP communication in ControlLogix systems, the Allen-Bradley 1756-ENBT/A (1756-ENBT/A communication module) provides direct physical and protocol-level execution of 10/100 Mbps industrial Ethernet frame handling, supporting TCP and CIP connection mapping between controllers and distributed I/O nodes across RJ45-based network infrastructure.

Suffix Breakdown & Model Matrix

No structured suffix decomposition is defined for 1756-ENBT/A. The “/A” revision denotes hardware revision level within the ControlLogix Ethernet communication module family.

Hardware Specifications

Backplane Bus Communication Velocity & EtherNet/IP Deterministic Network Behavior

Within ControlLogix chassis architectures, the 1756-ENBT/A executes cyclic backplane arbitration where Ethernet/IP frames are synchronized with controller task scheduling. CIP connection handling is mapped into implicit and explicit messaging queues, with up to 128 CIP connections processed through internal buffering logic. Backplane current consumption (800 mA at 5.1 VDC) defines slot-level power constraints that indirectly influence module population density and network interface loading. Deterministic communication timing is maintained through chassis scan alignment rather than standalone Ethernet timing control.

Frequently Asked Questions (FAQ)

Q: Does the 1756-ENBT/A support hot-swap replacement during runtime?
A: Hot-swap behavior is not specified in the provided data. Standard practice requires chassis power-down or controlled module replacement procedure.

Q: How does the module manage 64 TCP and 128 CIP connections simultaneously?
A: The module uses internal connection scheduling buffers to separate TCP socket handling from CIP implicit/explicit messaging queues.

Q: What is the impact of 800 mA backplane current draw?
A: The 800 mA at 5.1 VDC load contributes to chassis power budget consumption but does not directly limit Ethernet link speed.

Field Installation Guidelines

The module must be installed into a compatible 1756 ControlLogix chassis with correct slot alignment to ensure proper backplane connector engagement. RJ45 Ethernet cabling should use shielded twisted pair where noise coupling is present, with shield termination at a single cabinet ground point. Backplane connectors must be fully seated to avoid intermittent CIP session loss. Cable routing should maintain separation from high-voltage conductors to reduce EMI-induced packet jitter. Installation and replacement should follow ESD-safe handling procedures.