AB Allen-Bradley 1756-L55M16 Logix5555 Processor 7.5 MB Memory

Product Summary

The Allen-Bradley 1756-L55M16 is a ControlLogix Logix5555 Controller by Rockwell Automation, featuring 7.5 MB user memory and integrated serial communication. It is part of the second-generation ControlLogix 5550/5555 processor family, offering enhanced performance over the original Logix5550 with faster scan times and expanded memory capacity for complex industrial automation applications.

Core Specifications

• Model Number: 1756-L55M16
• Type: ControlLogix Logix5555 Controller
• User Memory: 7.5 MB
• I/O Capacity: 128,000 digital / 4,000 analog I/O points
• Analog Output (Max): 2,000
• Program Scan Time: 0.08 ms
• Chassis Slots: 4, 7, 10, 13, 17 (1756 series)
• Communication: RS-232 serial; EtherNet/IP, ControlNet, DeviceNet via 1756 communication modules
• Programming: RSLogix 5000
• Manufacturer: Allen-Bradley by Rockwell Automation

Electrical & Functional Characteristics

• Backplane Current: 1.23 A at 5 VDC; 14 mA at 24 VDC
• Power Dissipation: <6.2 W typical
• Task Types: Continuous, periodic, and event tasks
• Serial Port: RS-232 for DF1, DH-485, or ASCII protocols
• USB Port: Not included
• Status Indicators: RUN, FORCE, I/O status, and RS-232 activity LEDs
• Keying: Electronic keying prevents incorrect module insertion

System Integration & Compatibility

• Primary Platform: ControlLogix 1756 chassis
• Compatible I/O: All 1756-series digital, analog, specialty, and safety I/O modules
• Communication Modules: 1756-ENBT, 1756-EN2T, 1756-CNBR, 1756-DNB
• Redundancy: Compatible with 1756-RM redundancy modules for paired chassis configurations
• Software Version: RSLogix 5000 v16 or later
• Related Parts: 1756-L55M12 (750 KB), 1756-L55M13 (1.5 MB), 1756-L55M14 (3.5 MB), 1756-L55M24 (3.5 MB with M24 memory)

Environmental & Operational Limits

• Operating Temperature: 0°C to 60°C (32°F to 140°F)
• Storage Temperature: -25°C to +70°C (-13°F to 158°F)
• Humidity: 5% to 95% RH, non-condensing
• Vibration: 2G, 10 to 500 Hz
• Shock: 30G operating; 50G non-operating
• Approvals: UL Listed, CE, C-UL

Industrial Applications

Widely deployed in manufacturing, material handling, packaging, automotive assembly, food & beverage processing, water/wastewater treatment, and general industrial automation requiring medium to large program memory and high-speed control on the legacy ControlLogix 5555 platform.

Frequently Asked Questions

What is the 1756-L55M16 used for?

It is a ControlLogix Logix5555 processor with 7.5 MB user memory, designed for medium to large-scale industrial automation applications requiring substantial program capacity and fast scan times.

What is the difference between 1756-L55M16 and 1756-L55M14?

The 1756-L55M16 has 7.5 MB user memory. The 1756-L55M14 has 3.5 MB user memory. Both are Logix5555 processors with identical I/O capacity and communication capabilities.

Is the 1756-L55M16 still supported by Rockwell Automation?

No — the Logix5555 platform is legacy/obsolete. Rockwell Automation no longer manufactures or supports these processors. Replacement units must be sourced from authorized surplus dealers or refurbishment services. Consider migrating to the 1756-L7x or L8x series for new applications.

What battery does the 1756-L55M16 use?

The controller uses a 3V lithium battery (1756-BA1 or equivalent) to retain RAM data during power loss. Battery life is approximately 2–3 years under normal operating conditions.

What are the related part numbers?

• 1756-L55M12 — Logix5555, 750 KB memory
• 1756-L55M13 — Logix5555, 1.5 MB memory
• 1756-L55M14 — Logix5555, 3.5 MB memory
• 1756-L55M16 — Logix5555, 7.5 MB memory (this part)
• 1756-L55M24 — Logix5555, 3.5 MB memory (with M24 memory module)