Allen-Bradley 1756-ENET/A Ethernet Communication Module

Configured for Ethernet-based controller-to-device messaging in ControlLogix architectures, the Allen-Bradley 1756-ENET/A (1756-ENET/A Ethernet communication module) provides direct physical and network-level execution for TCP/IP communication over 10 Mbps industrial Ethernet within ControlLogix backplane systems.

This module operates as an early-generation Ethernet interface, bridging ControlLogix processors to standard Ethernet networks without full EtherNet/IP object modeling. It is positioned as a discontinued communication component, superseded by higher-capacity ENBT and EN2T modules with extended connection handling and diagnostics.

Hardware Specifications

ControlLogix Backplane and Ethernet Deterministic Behavior

Within the Allen-Bradley ControlLogix platform, the 1756-ENET/A module integrates through backplane bus arbitration, sharing controller memory access with I/O and communication modules. It supports early-stage Ethernet messaging but lacks modern EtherNet/IP cyclic I/O scheduling.

Backplane communication is constrained by legacy firmware architecture, limiting simultaneous socket handling and deterministic network scheduling compared to later 1756-ENBT/EN2T modules. Firmware execution does not support enhanced tag-based object modeling used in modern ControlLogix communication stacks.

Frequently Asked Questions (FAQ)

Q: Does the 1756-ENET/A support EtherNet/IP cyclic I/O communication?
A: No. It supports basic Ethernet TCP/IP messaging only and does not implement full EtherNet/IP object services.

Q: Can the module be hot-swapped in a running ControlLogix chassis?
A: Hot-swapping depends on system configuration and chassis rules. Backplane power must be managed according to ControlLogix slot power sequencing.

Q: Is firmware upgrade available for extending functionality?
A: No functional expansion is available. The module is discontinued and firmware is frozen at legacy revision levels.

Field Installation Guidelines

Install the module into a compatible 1756 ControlLogix chassis with power removed before insertion or removal unless system hot-swap is explicitly configured.

Ensure RJ-45 Ethernet cabling complies with industrial shielding practices, including proper shield termination at cabinet ground reference points. Maintain separation between Ethernet cabling and high-voltage power conductors to reduce EMI coupling.

Backplane slot alignment must be verified to avoid connector pin stress. Maintain ventilation clearance to ensure stable operation within 0 to 60 deg C ambient limits. Avoid bending stress on the RJ-45 connector during cable routing.