The 1756-L55M12 ControlLogix 5555 Processor Module from Rockwell Automation is a legacy yet highly dependable PLC CPU designed for industrial automation systems requiring stable logic execution, modular scalability, and long-term operational continuity.
This controller is part of the ControlLogix 5555 family and is widely used in installed-base environments such as manufacturing lines, utilities, and process automation systems. Even though it is discontinued, it remains essential in maintenance-driven architectures where system replacement is not immediately feasible.
Technical Specifications (Including Size & Weight)
| Parameter | Specification |
|---|---|
| Model | 1756-L55M12 |
| Series | ControlLogix 5555 |
| User Memory | 750 KB |
| I/O Memory | ~208 KB |
| Maximum I/O Capacity | Up to 128,000 points |
| Backplane Current (5V DC) | ~1.23 A |
| Backplane Current (24V DC) | ~14 mA |
| Power Dissipation | ~5.6 W |
| Communication | Requires external modules (EtherNet/IP, ControlNet, DH+) |
| Programming Software | RSLogix 5000 (legacy versions) |
| Battery | 1756-BA1 lithium backup battery |
| Operating Temperature | 0°C to 60°C |
| Storage Temperature | -40°C to 85°C |
| Humidity | 5%–95% non-condensing |
| Dimensions (H × W × D) | 13.3 × 5.1 × 14.5 cm |
| Weight | ~0.35 kg |
The module maintains a compact ControlLogix form factor, ensuring compatibility with standard chassis systems used in legacy industrial installations.
Recommended Related Models
For maintenance, replacement, or system expansion, the following modules are commonly paired with the 1756-L55M12:
- 1756-L61 ControlLogix CPU (modern upgrade path)
- 1756-ENBT EtherNet/IP Communication Module
- 1756-CNB ControlNet Bridge Module
- 1756-IB16 Digital Input Module
- 1756-OB16 Digital Output Module
Popular Allen-Bradley ControlLogix Models
Within the same ecosystem, engineers often work with:
- 1756-L1 / L1M legacy controllers
- 1756-L55 family processors
- 1756-L71 / L72 modern ControlLogix CPUs
- 1756-EN2T high-speed Ethernet modules
- 1756-DHRIO remote I/O communication modules
These modules represent the evolution of Rockwell’s ControlLogix platform across multiple industrial generations.
