Overview
The Allen-Bradley 1785-L86B is a PLC-5/86 processor module designed as the central processing unit for the PLC-5 controller platform. Manufactured by Rockwell Automation, this Series D unit delivers robust mid-to-large-scale industrial control for legacy applications. The 1785-L86B integrates into 1771 I/O chassis and supports advanced I/O management through Data Highway Plus (DH+) networking, making it ideal for established manufacturing environments that require continuity in automation infrastructure.
Key Features
- DH+ Networking: 4 DH+/Remote I/O ports (configurable as adapter or scanner mode) for flexible network architecture and distributed processing
- Protected Memory: Word-level memory protection capability to restrict access to critical or proprietary program areas
- Advanced Instruction Set: File handling, sequencer, diagnostic, shift register, immediate I/O, and program control instructions
- Multiple Main Programs: Support for segregation of independent control tasks with program-specific interrupts and global status flags
- Modular Architecture: Single-slot module integration into 1771 I/O chassis with flexible I/O configuration options
- Fault Response Programming: Timed interrupt routines and programmable fault handling to minimize downtime
Technical Specifications
- Processor Model: PLC-5/86
- Series: D
- Chassis Mount: Single-slot, leftmost position in 1771 I/O chassis
- Communication Ports: 4 DH+/Remote I/O (configurable)
- Max I/O Per Link: 32
- Universal Remote I/O: Compatible with 1771 I/O chassis, 1791 I/O blocks, and legacy devices
- Device Compatibility: PanelView displays, RediPANEL, Dataliner, 1336 drives
- Memory Protection: Word-selectable protection on this enhanced processor model
- Manufacturing Origin: United States
- Part Number: 97292372 A01
Typical Applications
The 1785-L86B processor excels in legacy industrial environments including:
- Manufacturing process control and sequencing
- Distributed I/O systems using Data Highway Plus networking
- Applications requiring protected memory and restricted access
- Systems needing multiple independent main control programs
- Retrofit and upgrade projects preserving existing PLC-5 infrastructure
Compatibility & Replacements
The 1785-L86B is part of the Allen-Bradley PLC-5 processor family, which includes models like 1785-L20, -L30, -L40, -L60, and -L80. The L86B variant offers enhanced memory protection features compared to earlier models. When evaluating replacements for legacy systems, consider that the entire PLC-5 platform architecture is modular—I/O chassis, communication modules, and programming software remain consistent across processor models. For systems migrating away from legacy control, Rockwell Automation’s ControlLogix and CompactLogix platforms offer modern alternatives, though direct hardware replacement typically requires reprogramming. This unit’s used condition makes it suitable for spare parts inventory, system expansion, or replacement in existing installations.
