Allen-Bradley 1785-L40C15 ControlNet PLC-5/40 Processor Module

The Allen-Bradley 1785-L40C15, also cataloged as the 1785-L40C15 ControlNet PLC-5/40 Processor Module, operates as a dedicated hardware component for centralized program execution and real-time network scheduled communication within Allen-Bradley 1771 Universal I/O chassis platforms.

Hardware Specifications

ControlNet Deterministic Network & Backplane Integration

The 1785-L40C15 integrates direct ControlNet Phase 1.25 connectivity to deliver deterministic, time-critical data transmission across peer processors and distributed I/O drops without relying on external bridge modules. Executing user programs from its internal 48k word SRAM, the unit communicates across the 1771 backplane bus to scan local digital and analog I/O cards while coordinating scheduled ControlNet network updates. The onboard hardware maintains deterministic scan times and link repeatability across noisy industrial environments, drawing 3.0 A at 5 VDC directly from the chassis power supply.

Frequently Asked Questions

Q: What is the backplane current consumption for the 1785-L40C15 module?

A: The 1785-L40C15 processor draws a maximum of 3.0 A at 5 VDC from the 1771 backplane power supply, which must be accounted for in total chassis power system calculations.

Q: How is user program memory retained in the event of external power loss?

A: System logic routines and data tables in the 48k word SRAM are preserved during power cycles by an internal lithium battery, preventing memory loss and maintaining system configuration state.

Field Installation Guidelines

1. Power Isolation: Turn off main AC power to the 1771 chassis power supply before inserting or removing the 1785-L40C15 processor to prevent backplane bus edge-connector pin damage.
2. Chassis Insertion: Align the module card edges with the top and bottom guides of the leftmost slot (Slot 0) in the 1771 Universal I/O chassis. Push firmly until the backplane connectors seat completely, then lock the chassis retaining latch.
3. ControlNet Coaxial Cabling: Connect ControlNet RG-6 quad-shield coaxial cable taps to the BNC ports. Ensure minimum cable bend radiuses are respected and maintain proper tap isolation.
4. Shield Grounding: Connect coaxial network cable shields to the main single-point plant ground system to eliminate ground loops and reduce EMI noise interference.
5. Battery Verification: Check the status of the backup memory battery before commissioning to ensure program data persistence during scheduled maintenance power outages.