Allen-Bradley 1756-ENET ControlLogix Ethernet Communication Module

The Allen-Bradley 1756-ENET, also cataloged as the 1756-ENET Ethernet communication module, operates as a dedicated hardware component for EtherNet-based CIP messaging and real-time I/O data exchange within ControlLogix 1756 chassis architectures.

Configured for scanner/adapter mode communication in ControlLogix systems, the Allen-Bradley 1756-ENET (1756-ENET communication module) provides direct physical and protocol-level execution of 10 Mbps Ethernet frame handling through 10BaseT and AUI interfaces, enabling CIP-based deterministic messaging and controller-to-I/O data transport across linear Ethernet topologies.

Suffix Breakdown & Model Matrix

No formal suffix segmentation is defined for 1756-ENET. The model identifier represents a fixed ControlLogix Ethernet communication module within the early-generation ControlLogix network family.

Hardware Specifications

Backplane Bus Communication Velocity & CIP Messaging Determinism

Within ControlLogix chassis systems, the 1756-ENET executes backplane-to-Ethernet translation where CIP messaging is mapped into deterministic scan-based cycles. The module separates scanner and adapter roles, allowing real-time I/O data exchange and explicit messaging through shared backplane arbitration. Backplane current consumption (900 mA at 5.1 VDC) defines slot-level loading constraints, while Ethernet throughput remains fixed at 10 Mbps, requiring cycle synchronization between controller task execution and network transmission buffering.

Channel-to-Channel Ethernet Isolation & Legacy Network Constraint Behavior

The 1756-ENET employs single-port 10BaseT and AUI physical layer separation, limiting concurrent traffic paths to a single linear topology. Signal integrity is maintained through dedicated TXD/RXD state indicators, reflecting frame-level transmission states. Legacy architecture constraints enforce strict CIP connection scheduling, where scanner/adapter mode switching defines communication directionality rather than full duplex multi-channel segmentation.

Frequently Asked Questions (FAQ)

Q: Does the 1756-ENET support hot-swapping during runtime operation?
A: Hot-swap behavior is not specified. Standard ControlLogix practice requires controlled chassis handling during module replacement.

Q: Can the module operate in parallel scanner and adapter roles simultaneously?
A: The module supports both functions, but execution is time-sliced within CIP scheduling rather than fully parallelized operation.

Q: Does backplane current (900 mA at 5.1 VDC) affect Ethernet throughput?
A: No direct impact on Ethernet bandwidth. It affects chassis power budget and slot loading only.

Field Installation Guidelines

The module must be installed into a compatible 1756 chassis (Series A or B) with correct slot alignment to ensure backplane connector integrity. Ethernet cabling for 10BaseT must maintain proper shielding continuity and separation from high-voltage conductors to reduce induced noise on AUI and RJ45 signaling paths. All connectors must be fully seated to avoid intermittent CIP communication faults. TXD and RXD LED states should be verified during commissioning to confirm physical layer activity. ESD handling procedures are required during insertion or removal.