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1756-L64
1756-L64
1756-L64

Allen-Bradley 1756-L64 ControlLogix 5564 CPU Module

  • Model: 1756-L64
  • Brand: Allen-Bradley (Rockwell Automation)
  • Series: ControlLogix 5560
  • Core Function: Execute PLC control logic and communications
  • Product Type: Processor (CPU) Module
  • Key Specs: 16 MB user memory, 478 KB I/O memory, CompactFlash support
  • ⚠️ Obsolete Model – Limited Stock Available
  • Condition: New Original / New Surplus or Refurbished (Tested)
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Description

Key Technical Specifications

Parameter Value
Product Type Processor (CPU) Module
Manufacturer Allen-Bradley / Rockwell Automation
Model Number 1756-L64
Product Series ControlLogix 5560
User Memory 16 MB
I/O Memory 478 KB
Optional Nonvolatile Memory 128 MB CompactFlash (1784-CF128)
Programming Software RSLogix 5000 / Studio 5000 (firmware dependent)
Communication Port One RS-232 Serial Port
Maximum Digital I/O 128,000 points
Maximum Analog I/O 4,000 points
Maximum Controller Connections 250
Backplane Current 1,200 mA @ 5.1 V DC; 14 mA @ 24 V DC
Power Dissipation 3.5 W
Isolation Voltage 30 V continuous (RS-232 to system)
Operating Temperature 0 to 60 °C
Storage Temperature −40 to 85 °C
Compatible Chassis 1756-A4, A7, A10, A13, A17

The Allen-Bradley 1756-L64 is a high-capacity ControlLogix 5560 controller with 16 MB of user memory for complex automation applications. Rockwell Automation officially discontinued the controller on June 1, 2017, and classifies its replacement as a functional migration rather than a direct hardware substitute.

 

Product Introduction

The Allen-Bradley 1756-L64 is a high-performance ControlLogix processor developed for large-scale discrete manufacturing, process control, material handling, and infrastructure automation systems. With 16 MB of user memory, it supports extensive control strategies, multiple tasks, large tag databases, and high I/O counts while maintaining deterministic execution.

Compared with lower-memory controllers such as the 1756-L61 and 1756-L62, the 1756-L64 provides additional application capacity for large production lines and integrated plant architectures. Many operating facilities continue to maintain spare units because replacing the processor is often less disruptive than performing a complete controller migration.

1756-L64

1756-L64

1756-L64

1756-L64

Installation & Configuration Guide

 

Stage 1 – Pre-Installation Preparation (Estimated Time: 15 Minutes)

⚠️ Safety First

  1. Notify operations of the planned maintenance window.
  2. Bring the process to a verified safe state.
  3. Apply lockout/tagout procedures.
  4. Remove power from the ControlLogix chassis.
  5. Wait 5 minutes for power supply capacitors to discharge.

Tools Required

  • Grounded ESD wrist strap
  • PH1 screwdriver
  • Fluke 115 digital multimeter
  • Laptop with RSLogix 5000 or Studio 5000
  • 1756-CP3 or 1747-CP3 serial cable
  • Smartphone for documenting wiring

Data Backup

  1. Upload the complete controller project.
  2. Record the controller firmware revision.
  3. Save communication parameters.
  4. Document chassis slot assignments.
  5. Verify CompactFlash contents if installed.
  6. Record battery condition.

 

Stage 2 – Removing the Old Controller (Estimated Time: 10 Minutes)

  1. Verify chassis power is OFF.
  2. Disconnect communication cables.
  3. Remove the CompactFlash card if required.
  4. Release the controller locking tabs.
  5. Remove the processor using straight, even pressure.
  6. Inspect the backplane connector for contamination or bent pins.

⚠️ Retain the original controller until the replacement completes commissioning successfully.

 

Stage 3 – Installing the New Controller (Estimated Time: 20 Minutes)

  1. Wear a grounded ESD wrist strap.
  2. Confirm the replacement part number is 1756-L64.
  3. Install the processor into the original chassis slot.
  4. Reinstall the CompactFlash card and battery if required.
  5. Connect the programming cable.
  6. Verify firmware compatibility.
  7. Restore the controller application if necessary.

Self-Checklist

  • Correct catalog number
  • Firmware verified
  • CompactFlash installed
  • Battery inspected
  • Controller fully seated

 

Stage 4 – Power-On & Testing (Estimated Time: 20 Minutes)

Pre-Power Checks

  • Verify chassis power supply output.
  • Inspect battery installation.
  • Verify CompactFlash seating.
  • Confirm serial communication settings.

Commissioning Steps

  1. Apply chassis power.
  2. Verify the OK and RUN LEDs.
  3. Connect using RSLogix 5000.
  4. Confirm controller identity.
  5. Verify firmware revision.
  6. Download or validate the application.
  7. Test local and remote I/O before returning the system to production.

⚠️ Troubleshooting Notes

  • Major Fault LED: Verify firmware compatibility before downloading the application.
  • Communication failure: Confirm serial cable type and communication parameters.
  • Project mismatch: Check controller revision and electronic keying.
  • Startup recovery issue: Verify the CompactFlash image and battery status. Firmware v20.019 is the latest firmware released for this controller.

Common Field Pitfalls

❗ Firmware Revision Mismatch

I’ve seen replacement projects delayed for days because someone assumed every L6x controller could run the same firmware. Always record the firmware revision before removing the original controller. Loading the wrong revision may prevent project downloads or create controller faults.

❗ CompactFlash Card Management

If the controller boots from CompactFlash, verify both the hardware and the stored image. An outdated image can overwrite a newer project during startup if automatic loading has been configured.

❗ Battery Condition

The controller depends on a healthy lithium battery for memory retention. Replace aging batteries during planned shutdowns instead of waiting for a low-battery alarm.

❗ Legacy Software Compatibility

The 1756-L64 supports specific RSLogix 5000 and Studio 5000 releases based on firmware revision. Installing the latest engineering software does not automatically guarantee compatibility with legacy projects.

❗ Electrostatic Discharge

Processor modules contain high-density components that can be damaged by static electricity. Always wear a grounded wrist strap and use an ESD-safe work surface.

Keep these checks in mind and you’ll avoid most ControlLogix processor replacement problems before production resumes.

 

Frequently Asked Questions (FAQ)

Q1. Is the Allen-Bradley 1756-L64 obsolete?

Yes.

Rockwell Automation discontinued the 1756-L64 on June 1, 2017. Repair services and technical documentation remain available, while replacement units are typically sourced from New Surplus inventory or professionally tested refurbished stock.

Q2. What is the replacement for the 1756-L64?

There is no direct drop-in replacement.

Rockwell designates newer ControlLogix controllers as functional replacements, meaning migration usually requires firmware validation, project conversion, and verification of communication modules, I/O modules, and engineering software compatibility.

Q3. Will replacing the controller erase my PLC program?

Not if proper backups exist.

Upload the complete project before removing the original controller. If the application relies on CompactFlash or battery-backed memory, verify both before beginning maintenance.

Q4. Why is New Surplus inventory priced below OEM distribution?

New Surplus inventory typically originates from canceled capital projects, unused maintenance stock, or plant modernization programs. The lower price reflects inventory sourcing rather than reduced functionality. Request the serial number, inspection records, firmware revision, and warranty documentation before purchasing.

Q5. How is each 1756-L64 tested before shipment?

Every controller should complete a documented quality inspection:

  1. Inbound Inspection & Traceability
    • Verify OEM labels and serial numbers.
    • Inspect enclosure, PCB, connectors, and backplane interface.
    • Check for corrosion, scratches, repairs, and UV discoloration.
  2. Functional Testing
    • Install the controller in a genuine ControlLogix chassis.
    • Verify startup diagnostics.
    • Test RS-232 communications.
    • Download and execute a validation project.
    • Perform continuous operation for more than 24 hours while monitoring processor stability.
  3. Electrical Testing
    • Verify insulation resistance where applicable.
    • Check ground continuity.
    • Measure power consumption.
  4. Firmware & Configuration Verification
    • Record firmware revision.
    • Verify CompactFlash functionality.
    • Confirm battery-backed memory retention.
  5. Final QC & Packaging
    • QC inspector approval.
    • Anti-static ESD packaging.
    • Heavy-duty corrugated shipping carton.
    • QC Passed label with inspection date.

Test reports, photographs, and functional test videos should be available upon request.

Q6. Which programming software supports the 1756-L64?

The controller supports RSLogix 5000 and compatible Studio 5000 releases that match the installed firmware. Firmware v20.019 is the latest firmware published for the 1756-L64, so engineering software should be selected accordingly.

Q7. What should I verify before installing a replacement 1756-L64?

Before commissioning, verify:

  • Exact catalog number (1756-L64)
  • Firmware revision
  • Controller project backup
  • RSLogix 5000 or Studio 5000 compatibility
  • CompactFlash card contents
  • Battery condition
  • Chassis slot assignment
  • Power supply capacity

From practical field experience, most commissioning delays after replacing a 1756-L64 result from firmware mismatches, outdated CompactFlash images, or missing project backups—not from processor hardware failures. Spending a few extra minutes documenting the original controller before removal usually prevents hours of recovery work.

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