Product Overview

The Allen-Bradley 1785-L40E is a high-performance Ethernet-enabled central processing unit belonging to the renowned PLC-5 family. Designed for sophisticated automation requirements, this controller serves as the intelligence core within a 1771 Universal I/O chassis. It is specifically engineered to bridge the gap between legacy control architectures and modern plant-wide networking by integrating an onboard 10/100 Mbps Ethernet interface. This allows the 1785-L40E to facilitate high-speed data exchange with supervisory systems, HMI interfaces, and other peer-to-peer controllers without the need for external bridge modules.

This CPU is a versatile solution for managing medium-to-large scale industrial processes. It provides robust execution of complex control logic, including proportional-integral-derivative (PID) loops for process regulation, advanced math instructions, and extensive data handling. Its structural compatibility with 1771-A1B, A2B, and A4B chassis ensures that existing PLC-5 users can upgrade their communication capabilities while retaining their proven I/O hardware and field wiring infrastructure.

Multi-Protocol Communication and Networking

The 1785-L40E excels in network connectivity, offering a diverse array of ports to support multi-tier communication strategies. In addition to the dedicated Ethernet port, the module features two configurable Data Highway Plus (DH+) or Remote I/O (RIO) combination ports. These allow the processor to function simultaneously as a scanner for distributed I/O racks and as a node on a peer-to-peer DH+ plant network.

For local device integration, a multi-standard serial port is provided, supporting RS-232, RS-422A, and RS-423 protocols. This comprehensive I/O capability allows the 1785-L40E to manage up to 2048 discrete I/O points across as many as 61 remote chassis. With its deterministic background scan and high-speed local I/O processing (as low as 0.5ms), the controller maintains tight synchronization in time-critical applications such as automotive assembly, material handling, and food processing.

Technical Specifications

• Manufacturer: Allen-Bradley (Rockwell Automation)

• Model Identification: 1785-L40E

• Product Line: PLC-5 Enhanced Ethernet

• User Memory: 48,000 words (48KW)

• I/O Capacity: 2048 total inputs/outputs (any mix)

• Max I/O Racks: 61 Remote I/O chassis

• Ethernet Speed: 10/100 Mbps (RJ45)

• DH+ / RIO Ports: 2 Combination Channels

• Serial Interface: 1 Port (RS-232C, RS-422A, RS-423)

• Backplane Current: 3.3A @ 5V DC

• Thermal Output: 17.3 Watts (59.1 BTU/hr)

• Operating Temp: 0 to 60°C (32 to 140°F)

• Certifications: UL, CSA, CE, C-Tick

• Dimensions: 4.8 x 16.7 x 27.4 cm

• Weight: 1.38 kg

Programming and Operational Logic

• Logic Execution: Supports IEC 61131-3 compatible languages including Relay Ladder Logic, Structured Text, and Sequential Function Charts (SFC).

• Data Integrity: Includes internal diagnostics and status flags for monitoring CPU health, battery levels, and communication integrity.

• Industrial Hardening: Designed for 24/7 operation in harsh environments with significant vibration and electromagnetic interference (EMI) resistance.

• Memory Backup: Supports EEPROM modules for non-volatile program storage and automatic recovery during power cycles.