Allen-Bradley 1756-L61 – ControlLogix Processor Module

The Allen-Bradley 1756-L61 is a ControlLogix processor module. Specifically, this controller belongs to the ControlLogix series from Rockwell Automation. It is available in both Series A and Series B variants. Furthermore, it features fixed memory options of 2, 4, or 8 MB. In addition, it includes 2 MB of user memory and 478 KB of I/O memory. Therefore, this processor suits medium-scale control applications with extensive I/O requirements.

Ordering Configuration and Product Identification

• Manufacturer: Rockwell Automation.

• Brand: Allen-Bradley.

• Part Number: 1756-L61.

• Series: ControlLogix.

• Module Type: Processor Module.

• User Memory: 2 MB.

• I/O Memory: 478 KB.

• Fixed Memory Options: 2, 4, or 8 MB.

• Maximum Digital I/O: 128,000.

• Maximum Analog I/O: 4,000.

• Maximum Total I/O: 128,000.

• UPC: 10612598300706.

• UNSPSC: 32151705.

• Lifecycle Status: Discontinued/Obsolete.

• Consequently, the Allen-Bradley 1756-L61 remains available only through aftermarket suppliers.

Nonvolatile Memory and CompactFlash

• Nonvolatile Memory Type: Compact Flash card (optional).

• Supported Card: 1784-CF128 only.

• Maximum Capacity: 128 MB.

• Purpose: Backup storage for user programs and data.

• Installation: Insert card into controller front slot.

• Compatibility: Only the 1784-CF128 is certified.

• Risk: Other cards may cause data corruption.

• Application: Program storage and retrieval.

• Recommendation: Always use Rockwell Automation certified cards.

• Thus, the 1756-L61 provides optional nonvolatile memory for reliable program backup.

Chassis Compatibility

• 1756-A4: Compatible (4-slot).

• 1756-A7: Compatible (7-slot).

• 1756-A10: Compatible (10-slot).

• 1756-A13: Compatible (13-slot).

• 1756-A17: Compatible (17-slot).

• Chassis Location: Any available slot.

• Enclosure Type: Open-style (requires chassis).

• Modularity: Easy system modification and tailoring.

• Cost Reduction: Users can customize according to requirements.

• System Configurations: Independent controller, multiple controllers in one chassis, or networked controllers.

• Multi-controller Support: Several controllers can operate in combination through network communication.

• Multi-platform I/O: Supports various I/O platforms simultaneously.

• Therefore, the 1756-L61 fits all standard ControlLogix chassis.

Backplane Current and Power Specifications

• Backplane Current (5 Volts DC): 1.2 Amps (1200 mA).

• Backplane Current (24 Volts DC): 14 milliamps.

• Power Dissipation: 3.5 Watts.

• Thermal Dissipation: 11.9 BTU per hour.

• Continuous Isolation Voltage: 30 Volts.

• Isolation Test: 720 Volts DC for 60 seconds.

• Weight: 0.32 kg (0.71 pounds).

• Program Scan Time: 0.08 milliseconds.

• Form Factor: Small and cost-effective package.

• Consequently, the 1756-L61 provides fast scan times with moderate power consumption.

RS-232 Serial Communication

• Communication Port: Built-in RS-232 serial port.

• DF1 Full Duplex: Supported.

• DF1 Half-Duplex: Supported.

• DF1 Radio Modem: Supported.

• DH-485: Supported.

• Modbus via Logic: Supported.

• ASCII: Supported.

• Communication Cable: 1756-CP3 or 1747-CP3.

• Cable Length: 3 meters (9.84 feet).

• Connector Type: Right-angle to controller, straight to serial port.

• Optional Networks: EtherNet/IP, ControlNet, DeviceNet, Data Highway Plus, SynchLink, Remote I/O, third-party networks.

• Third-party Support: Includes process and device networks.

• Thus, the 1756-L61 offers versatile serial connectivity for programming and networking.

Battery Backup

• Battery Type (Series A): 1756-BA1, 1756-BATM, or 1756-BATA.

• Battery Type (Series B): 1756-BA2.

• Function: Retains user program and data during power loss.

• Replacement: Battery can be replaced when it wears out.

• Maintenance: Periodic battery checks are highly recommended.

• Battery Life: Depends on operating temperature and conditions.

• Application: Critical for program retention during power outages.

• Wear-out Indicator: Monitor battery status via programming software.

• Therefore, the Allen-Bradley 1756-L61 requires regular battery maintenance for reliable memory retention.

Controller Tasks and Connections

• Maximum Controller Connections: 250.

• Maximum Tasks: 32 tasks total.

• Maximum Programs per Task: 100 programs.

• Event Tasks: All event triggers are supported.

• Motion Support: Embedded SERCOS interface.

• Motion Analog Inputs: Encoder input, LDT input, and SSI input.

• Motion over Ethernet/IP: Supported with Ethernet communication module.

• Redundancy Support: Yes, for critical system availability.

• Stand-alone I/O: Supported for simple applications.

• Distributed I/O: Supported via network communication.

• Performance Enhancement: Additional modules can be installed for improved capability.

• Specialty Modules: Communication, intelligent, and encompass partner modules.

• Consequently, the 1756-L61 handles complex, multi-tasking applications effectively.

Programming Languages

• Relay Ladder: Supported.

• Structured Text: Supported.

• Function Block Diagram (FBD): Supported.

• Sequential Function Chart (SFC): Supported.

• IEC 61131-3 Compliance: Yes.

• Flexibility: Multiple languages can be used within the same project.

• Code Reuse: User-defined function blocks are supported.

• Application: Ideal for most medium-scale processes within I/O capacity.

• Programming Software: RSLogix 5000 or Studio 5000.

• Therefore, the 1756-L61 supports all major PLC programming languages for maximum flexibility.

Temperature and Environmental Ratings

• Operating Temperature Range: 0°C to 60°C (32°F to 140°F).

• Storage Temperature Range: -40°C to 85°C (-40°F to 185°F).

• Maximum Surrounding Air Temperature: 60°C.

• Relative Humidity: 5% to 95% non-condensing.

• Vibration: 2G at 10 to 500 Hz.

• Operating Shock: 30G.

• Non-operating Shock: 50G.

• Enclosure Type: Open-style (must be installed in a chassis).

• Chemical Resistance: Avoid direct exposure to harsh chemicals.

• Installation Environment: Suitable for industrial control panels.

• Moreover, the Allen-Bradley 1756-L61 withstands typical industrial environments reliably.

Installation Guide

First, verify that all system power sources are completely disconnected. Then, select an available slot in your ControlLogix chassis. The 1756-L61 can be placed in any slot. After that, slide the processor module into the chosen slot. Push firmly until the backplane connector is fully seated. Next, install the 1784-CF128 CompactFlash card for optional nonvolatile memory. Use only this certified card to prevent data corruption. Then, install the appropriate battery (1756-BA1, BA2, BATM, or BATA) for memory retention. After that, connect your RS-232 programming device using a 1756-CP3 or 1747-CP3 cable. Connect the right-angle end to the controller and the straight end to your serial port. Subsequently, apply power to the ControlLogix chassis. The processor will then begin its power-up sequence. After that, download your control program using RSLogix 5000 or Studio 5000 software. Select your preferred programming language (relay ladder, structured text, function block, or SFC). Then, configure the appropriate communication networks as needed. For redundant configurations, pair this controller with an identical unit for high availability. Finally, test all I/O connections and communication paths thoroughly. As a result, the Allen-Bradley 1756-L61 will provide reliable control for medium-scale processes.

Packaging List

• One Allen-Bradley 1756-L61 ControlLogix processor module

• One product identification label

• One installation and configuration guide

• Battery (purchased separately per series)

• CompactFlash card (purchased separately)

Common FAQs

Q1: What memory options does the Allen-Bradley 1756-L61 provide?
A: This processor provides 2 MB of user memory and 478 KB of I/O memory. Fixed memory options include 2, 4, or 8 MB depending on the variant. Therefore, it supports 128,000 digital I/O and 4,000 analog I/O.

Q2: What CompactFlash card is compatible with the 1756-L61?
A: This controller uses only the 1784-CF128 CompactFlash memory card. The maximum nonvolatile memory capacity is 128 MB. Therefore, other CF cards may cause data corruption or loss.

Q3: What communication port does the Allen-Bradley 1756-L61 have?
A: This processor has a built-in RS-232 serial communication port. Supported protocols include DF1 full/half-duplex, DF1 radio modem, DH-485, Modbus via logic, and ASCII. The recommended cable is 1756-CP3 or 1747-CP3.

Q4: Is the 1756-L61 still in production?
A: No, the product lifecycle status is discontinued or obsolete. However, the 1756-L61 remains available through aftermarket suppliers. Always verify compatibility before purchasing used units.

Q5: What battery does the Allen-Bradley 1756-L61 require?
A: Series A controllers use 1756-BA1, 1756-BATM, or 1756-BATA batteries. Series B controllers use the 1756-BA2 battery. Therefore, verify your controller series before ordering replacement batteries.