The Allen-Bradley 1785-L20C15, also cataloged as the PLC-5/20C ControlNet Processor Module, operates as a dedicated hardware component for processor execution and ControlNet communication management within PLC-5 control platforms.

Model Identification

The 1785-L20C15 is a PLC-5/20C processor module configured with ControlNet communication capability. It provides processor execution, memory handling, and network communication functions through the PLC-5 architecture.

The module contains 16K words of SRAM memory and supports connection to PLC-5 I/O systems through the 1771 chassis backplane.

Hardware Specifications

Industrial Control Communication Architecture

The 1785-L20C15 integrates ControlNet communication functions into the PLC-5 processor platform. The module manages deterministic network communication between PLC-5 controllers, remote I/O devices, and ControlNet connected equipment.

Allen-Bradley PLC-5 processors use backplane bus communication for data exchange between processor memory, I/O modules, and communication interfaces. The processor design supports modular I/O density scaling through 1771 series chassis configurations.

The ControlNet interface enables scheduled and unscheduled communication traffic management within industrial control networks. Network configuration depends on the connected ControlNet devices, node settings, and controller programming environment.

Ordering Information

• 1 x Allen-Bradley 1785-L20C15 PLC-5/20C ControlNet Processor Module
• Processor module memory: 16K words SRAM
• PLC-5 chassis mounting hardware is not included unless specified
• Programming cables, software, and manuals are not included unless listed separately

Field Installation Guidelines

Chassis Mounting

• Power down the PLC-5 chassis before installing or removing the processor module.
• Install the processor module into the compatible 1771 chassis slot position.
• Verify that the backplane connector is fully engaged before applying power.

Network Connection

• Connect ControlNet communication cables according to the ControlNet installation requirements.
• Maintain proper cable routing separation from high-voltage power wiring.
• Verify network node configuration before placing the processor into operation.

Configuration Requirements

• Confirm PLC-5 processor compatibility with the installed firmware revision.
• Verify I/O addressing configuration matches the application program.
• Use compatible PLC programming software for processor configuration and diagnostics.

Frequently Asked Questions

• What is the main function of the 1785-L20C15?

The 1785-L20C15 is a PLC-5/20C processor module that executes control programs and manages ControlNet communication functions.

• Does the 1785-L20C15 support ControlNet networks?

Yes. The module is designed for PLC-5 ControlNet applications and communicates with compatible ControlNet devices.

• What memory capacity does this processor provide?

The module contains 16K words of SRAM memory for processor program and data storage.

• What PLC family uses the 1785-L20C15?

The module belongs to the Allen-Bradley PLC-5 family and operates with compatible 1771 chassis systems.

• Can the module be installed while the chassis is powered?

No. Power should be removed before installation or removal to prevent processor or backplane faults.

• What I/O addressing method is supported?

The processor supports 2-slot addressing for compatible 1771 I/O module configurations.

• What power supply options are specified for this module?

The PLC-5 system supports 85-265V AC or 24V DC power supply configurations according to system design.

• Does the processor support analog and digital I/O modules?

Yes. Compatible PLC-5 configurations support 16/32-point digital modules and 4/8-channel analog modules.