Allen-Bradley 1756-L55M12 750KB Memory Processor – ControlLogix 5000 Series
When a ControlLogix processor fails mid-shift, the consequences are immediate and measurable: production lines halt, safety interlocks go into undefined states, and maintenance teams face mounting pressure with no clear timeline for recovery. In high-throughput manufacturing and process environments, the CPU is not a replaceable commodity — it is the deterministic core that every I/O module, drive, and HMI depends on for synchronized execution. A missing or counterfeit replacement compounds the problem rather than solving it.
The 1756-L55M12 occupies a well-established position within the ControlLogix 5000 platform: a mid-range processor offering 750KB of user memory, sufficient for complex multi-axis motion programs, redundant I/O trees, and structured text routines running concurrently. Introduced as part of the Logix5555 generation, this module remains widely deployed across automotive assembly, oil & gas SCADA, and water treatment facilities globally, where proven firmware stability is valued over migrating to newer hardware mid-lifecycle.
Technical Specifications
Electrical
- Backplane Current Draw: 800 mA @ 5 VDC; 3 mA @ 24 VDC
- Power Dissipation: 4.15 W (typical)
- Backplane Compatibility: 1756 ControlLogix chassis (all slot counts)
Memory & Processing
- User Memory: 750 KB
- I/O Memory: Shared from user memory pool
- Tasks Supported: Continuous, periodic, and event-driven (up to 32 tasks)
- Programs per Task: Up to 100
- Communication Connections: Up to 250 (combined local and remote)
Mechanical
- Form Factor: Single-slot ControlLogix module
- Dimensions: Standard 1756 chassis slot profile
- Weight: 340 g (approx.)
- Keying: Electronic keying supported via RSLogix 5000 / Studio 5000
Environmental
- Operating Temperature: 0 °C to 60 °C
- Storage Temperature: -40 °C to 85 °C
- Relative Humidity: 5% to 95% non-condensing
- Vibration: IEC 68-2-6 compliant
- Shock: IEC 68-2-27 compliant
Certifications
- UL Listed, CE Marked, C-Tick
- ATEX Zone 2 (with appropriate enclosure)
- Compliant with IEC 61131-3 programming standard
Key Features & Benefits
- 750 KB User Memory — Supports complex ladder logic, function block, and structured text programs simultaneously without memory fragmentation, reducing program partitioning overhead by eliminating the need for external memory cards on most mid-scale applications.
- Up to 250 Communication Connections — Enables direct EtherNet/IP, ControlNet, and DeviceNet connectivity through bridge modules in the same chassis, supporting distributed I/O trees across multiple remote racks without additional gateway hardware.
- IEC 61131-3 Multi-Language Programming — Engineers can mix ladder diagram, structured text, function block diagram, and sequential function chart within a single project, reducing migration effort when standardizing legacy relay logic alongside modern motion routines.
- Electronic Keying — Prevents accidental module substitution during maintenance; configurable to Exact Match, Compatible Module, or Disabled, meeting IEC 62443 change-management requirements for critical infrastructure.
- Deterministic Scan Time — Periodic tasks execute with ±0.1 ms jitter, a requirement for coordinated multi-axis servo control and high-speed packaging lines where timing drift causes product rejects.
- Firmware Stability for Long-Lifecycle Plants — The Logix5555 firmware series has been in production for over a decade; plants operating under IEC 61511 functional safety management plans can maintain validated firmware versions without forced upgrades.
Industry & Equipment Applications
- Automotive Assembly — Body-in-white welding lines, transfer press sequencing, and paint shop conveyor control where deterministic multi-task execution is mandatory.
- Oil & Gas — Wellhead control panels, pipeline SCADA remote terminal units, and compressor station automation requiring ATEX-compatible enclosure configurations.
- Water & Wastewater Treatment — Pump station sequencing, chemical dosing control, and SCADA integration over EtherNet/IP for municipal utilities with 24/7 uptime requirements.
- Food & Beverage Processing — CIP (Clean-in-Place) cycle management, filling line synchronization, and batch recipe execution under FDA 21 CFR Part 11 audit trail requirements.
- Power Generation & Utilities — Turbine auxiliary control, switchgear automation, and substation SCADA where long mean-time-between-failure (MTBF) is a procurement criterion.
- Mining & Minerals Processing — Conveyor belt management, crusher sequencing, and flotation cell control in high-vibration, dusty environments using sealed enclosures.
System Integration & Compatible Parts
Upstream / Power & Chassis:
- 1756-A4, 1756-A7, 1756-A10, 1756-A13, 1756-A17 — ControlLogix chassis (4 to 17 slots)
- 1756-PA72, 1756-PB72 — AC and DC power supplies for the 1756 chassis
Downstream / Communication & I/O:
- 1756-EN2T, 1756-EN2TR — EtherNet/IP communication modules (standard and ring topology)
- 1756-CN2, 1756-CN2R — ControlNet communication modules
- 1756-DNB — DeviceNet bridge module
- 1756-IB16, 1756-OB16E — Digital input/output modules
- 1756-IF8, 1756-OF8 — Analog input/output modules
Equivalent / Replacement Considerations:
- 1756-L55M13 (1 MB) — Direct upgrade path; same firmware family, larger memory pool. Suitable when user program exceeds 700 KB utilized.
- 1756-L61 (ControlLogix 5561, 2 MB) — Next-generation processor; requires Studio 5000 v16+ and firmware migration. Not a drop-in replacement without project conversion.
- 1756-L55M10 (512 KB) — Downgrade option for smaller programs; verify memory utilization before substitution.
Our Quality Assurance Process
- Visual & Physical Inspection — Each unit is examined for board-level damage, counterfeit markings, and tampered firmware labels. Modules with non-OEM labels or reground date codes are rejected at intake.
- Functional Power-On Test — The processor is seated in a live 1756 chassis, powered up, and verified to enumerate correctly via RSLogix 5000 / Studio 5000. Firmware version is confirmed and logged.
- Communication Verification — EtherNet/IP connectivity is tested through a 1756-EN2T bridge; the module must establish a Class 1 connection and respond to explicit messaging without errors.
- Documentation & Traceability — Each unit ships with a test report. Upon request, we can provide: original factory test certificate (if available), firmware version record, inspection checklist, and photos of serial number and date code.
How to Order
- Submit Your Inquiry — Contact us via the form on this page or email support@konmask.com with your required quantity, delivery timeline, and any specific firmware version requirements.
- Receive Your Quote — Our technical team reviews your request and responds within 24 hours with pricing, lead time, and available stock confirmation.
- Confirm & Ship — Upon order confirmation, we arrange packaging, export documentation, and your preferred freight method. Tracking is provided upon dispatch.
Why Choose Konmask.com?
- Specialist Focus — We source and supply industrial automation components exclusively, with deep familiarity in Allen-Bradley, Siemens, Schneider, and Mitsubishi product lines.
- Rigorous Inspection — Every module passes a documented 4-step QA process before shipment. We do not list untested stock.
- Technical Pre-Sales Support — Our team can advise on firmware compatibility, chassis slot planning, and equivalent substitutions before you commit to a purchase.
- Global Export Experience — We handle export documentation, commercial invoices, and packing lists for customers across Southeast Asia, the Middle East, and Europe.
- Responsive Communication — All inquiries receive a substantive response within 24 business hours, with a dedicated contact for follow-up questions.
Frequently Asked Questions
Q: Is the Allen-Bradley 1756-L55M12 compatible with Studio 5000 Logix Designer, or only RSLogix 5000?
A: The 1756-L55M12 is fully supported by RSLogix 5000 (v13 and later) and Studio 5000 Logix Designer (v21 and later). If you are using Studio 5000 v21+, the project will open in compatibility mode and retain all existing logic without modification. Confirm your software version before ordering if firmware matching is required.
Q: Can the 1756-L55M12 processor be used in a ControlLogix redundancy system?
A: The Logix5555 (1756-L55 series) does not natively support the ControlLogix Redundancy System (which requires 1756-L6x or later with 1756-RM redundancy modules). If your application requires hot-standby redundancy, the 1756-L61 or 1756-L62 with a 1756-RM2 module is the appropriate platform. Contact us to discuss your redundancy architecture before selecting a replacement processor.
Q: What is the lead time for the Allen-Bradley 1756-L55M12 and do you ship internationally?
A: Lead time depends on current stock levels and is confirmed at the time of inquiry — typically 3 to 10 business days for in-stock units. We ship internationally via DHL, FedEx, and UPS, with full export documentation provided. Submit an inquiry through Konmask.com for a specific delivery estimate to your location.
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Contact: support@konmask.com | +0086 19859288691
