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Allen-Bradley 1785-L40E Ethernet PLC-5 Processor Module

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Part Number: 1785-L40E
Brand: Allen-Bradley
Type: CPU Processors
Barcode: USA

Tags: Allen-Bradley PLC-5 , CPU Processors

Product Description

Configured for high-speed logic processing and Ethernet network integration in 1771 Universal I/O chassis platforms, the Allen-Bradley 1785-L40E (1785-L40E Ethernet PLC-5 Processor Module) provides direct physical execution of discrete, analog, and advanced PID loop control tasks.

Hardware Specifications

Parameter	Specification
Model	1785-L40E
Brand	Allen-Bradley
Origin	USA
Weight	3.75 lbs (1.70 kg)
Dimensions	Standard 1771 Single-Slot Module
Operating Temp	0 to 60 deg C (32 to 140 deg F)
Non-Operating Temp	-40 to 85 deg C (-40 to 185 deg F)
Power Dissipation	17.3 W
Input Voltage	5 VDC (Backplane)
Backplane Current Draw	3.3 A @ 5 VDC max
User Memory	48k Words SRAM (Battery-Backed)
Program Memory Backup	Optional EEPROM (1785-ME16, -ME32, -ME64, -M100)
Battery Module	1770-XYC
Maximum I/O Capacity	2048 Total I/O (any mix) or 2048 In / 2048 Out (complementary)
Max Analog I/O	2048
Max Total Chassis	61 (1 Local, 60 Universal Remote)
Embedded Communication Ports	1 Ethernet (10/100 Mbps), 2 DH+/Remote I/O (Configurable Scanner/Adapter), 1 Serial (RS-232/423/422A)
Compatible Chassis / Power	1771-A1B, -A2B, -A3B, -A3B1, -A4B / 1771-P4S, -P6S, -P4S1, -P6S1

Deterministic Backplane Bus & Network Architecture

The 1785-L40E processor resides in the primary slot of a 1771 chassis, interfacing via the 1771 backplane bus to control up to 2048 discrete or analog I/O points across 61 maximum chassis. Operating with determinism across its integrated Ethernet interface and dual DH+/Remote I/O ports, the module achieves Remote I/O rack scan speeds from 10 ms at 57.6 kbps down to 3 ms at 230.4 kbps. Internal 48k word battery-backed SRAM stores application ladder routines, function blocks, and register tables, maintaining memory state via an onboard 1770-XYC battery assembly. High I/O density scaling is supported through 2-slot, 1-slot, and half-slot addressing modes across local and remote chassis links.

Frequently Asked Questions

Q: What is the backplane power supply requirement for the 1785-L40E processor?

A: The 1785-L40E draws 3.3 A at 5 VDC from the 1771 backplane power supply and dissipates up to 17.3 W of power. Chassis power supply selection (such as 1771-P4S or 1771-P6S) must accommodate this current load along with installed I/O modules.

Q: How is memory retention preserved on the 1785-L40E during power interruption?

A: System program memory and registers are maintained by an onboard 1770-XYC lithium battery. For permanent non-volatile backup, optional EEPROM modules (1785-ME16, 1785-ME32, 1785-ME64, or 1785-M100) can be installed directly into the processor socket.

Field Installation Guidelines

Power Isolation: Always disconnect 1771 chassis power supply primary power before inserting or extracting the 1785-L40E module to prevent backplane edge-connector damage or transient electrical disruption.
Module Mounting: Slide the processor into Slot 0 of a compatible 1771 Universal I/O chassis (1771-A1B through 1771-A4B). Engage the top and bottom card locking levers firmly to ensure complete seating into the backplane connectors.
Ethernet and Field Wiring: Route Ethernet network cabling and DH+/RIO twinaxial shielded cables in dedicated wire raceways separated from high-voltage AC lines. Ground the cable shield at a single chassis grounding point to prevent high-frequency noise interference.
Battery Connection: Connect the 1770-XYC battery harness prior to powering up the system for initial configuration. Verify the BATT LED on the front panel remains unlit after power-up.
Keyswitch Operation: Adjust the 3-position keyswitch (RUN, PROG, REM) to the desired access level after verifying system communication settings in RSLogix 5.