1785-L80B | Allen-Bradley | PLC-5/80 Enhanced Processor Unit

Product Overview

The 1785-L80B  is a high-performance, enhanced processor within the Allen-Bradley PLC-5 platform. Designed for large-scale industrial control, the 1785-L80B features a robust memory capacity of 100,000 words and supports extensive I/O configurations. This processor is particularly noted for its versatility in communication, offering multiple Data Highway Plus (DH+) and Remote I/O (RIO) ports, making it a cornerstone for legacy system migrations and complex standalone automation cells.

Technical Specifications

• Manufacturer Allen-Bradley / Rockwell Automation

• Product Series PLC-5 Enhanced

• Model Number 1785-L80B

• Processor Variant PLC-5/80

• User Memory Capacity 100 Kilowords (100K)

• Standard Memory Type Battery-backed Static RAM

• Non-Volatile Backup Compatible with 1785-ME16, -ME32, -ME64, and -M100 EEPROM modules

• Maximum I/O Capacity 3,072 total (any mix of inputs and outputs)

• Maximum Analog I/O 3,072 points

• Universal Remote I/O Racks 32 Max per I/O link

• Total I/O Chassis Support 93

• Communication Ports Four (4) DH+/RIO (Scanner or Adapter), One (1) Serial port (RS-232, RS-423, RS-422A)

• Supported Protocols DH+, RIO, DF1, and ASCII

• Backplane Current (5V DC) 2.3 Amperes

• Power Dissipation 12 Watts

• Redundancy Support Fully compatible with PLC-5 backup hardware

• Weight 3.00 lbs (1.36 kg)

Performance and Network Timing

The 1785-L80B provides high-speed data processing across its remote I/O links. The scan time per rack is highly dependent on the communication baud rate configured:

• 57.6 kbits/s: 10 ms per rack

• 115.2 kbits/s: 7 ms per rack

• 230.4 kbits/s: 3 ms per rack

This deterministic performance allows engineers to tune the network for specific application requirements, balancing distance against speed.

Installation and Maintenance

The 1785-L80B is a modular component that installs into the leftmost slot (Slot 0) of a 1771 Universal I/O chassis.

• Battery Replacement: Uses the 1770-XYC lithium battery. It is recommended to replace the battery while the processor is powered to avoid data loss in the Static RAM.

• Memory Expansion: For applications requiring additional storage or dedicated backup, the processor supports the 1785-ME series of memory expansion modules.

• Environment: Designed for standard industrial environments with an operating temperature range of 0–60°C (32–140°F).

Frequently Asked Questions

• Can the 1785-L80B be used in a remote I/O chassis as an adapter?

  Yes, the ports are configurable. The processor can act as a Scanner to control local I/O or as an Adapter to communicate with a supervisory controller on a DH+ or RIO network.

• Is the memory protected against unauthorized edits?

  No, the 1785-L80B does not feature "Protected Memory" hardware locks. Security is typically managed through software permissions in RSLogix 5 or via physical keyswitch positions.

• What is the difference between the 1785-L80B and the standard 1785-L40B?

  The 1785-L80B provides significantly higher memory (100K vs 48K) and double the I/O capacity (3072 vs 2048), making it suitable for much larger system architectures.