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Product Overview
The 1756-L1 is a programmable automation controller (PAC) manufactured by Allen-Bradley, the flagship industrial automation brand of Rockwell Automation, and represents the original entry point into the ControlLogix 5550 processor family. Designed around the Logix5550 architecture and fitted with 64 KB of user memory, the 1756-L1 executes ladder logic, function block diagrams, sequential function charts, and structured text in accordance with IEC 61131-3, giving engineers a single controller environment for sequential control, loop regulation, batch management, and drive integration across a wide range of manufacturing applications.iqelectro.com
Occupying a single slot in any 1756 ControlLogix chassis — from the compact 1756-A4 through the 17-slot 1756-A17 — the 1756-L1 communicates across the high-speed ControlLogix backplane to local I/O, communication bridges, and other controllers, and multiple 1756-L1 units can reside in the same chassis while operating independently. An integrated RS-232 serial port supports DF1 and DH-485 protocols for direct programming, HMI attachment, and SCADA connection, while optional communication modules extend the controller onto EtherNet/IP, ControlNet, DeviceNet, and DH+ networks. Together, the platform supports up to 128,000 discrete I/O points and 4,000 analog I/O points depending on chassis and communication configuration.iqelectro.com
The controller accepts the 1756-M1, 1756-M2, or 1756-M3 nonvolatile memory board for program retention through power loss, and retains the working image through a 1756-BA1 or 1756-BA2 battery. Programming is performed through RSLogix 5000 (or Studio 5000 Logix Designer) via the 1756-CP3 serial cable, with the same software environment shared by every later ControlLogix generation — a deliberate architectural decision that gives the 1756-L1 an enduring role in legacy fleets even as newer processors have succeeded it.iqelectro.com
As the first-generation ControlLogix controller, the 1756-L1 remains a critical spare-part item for the thousands of plants worldwide that still operate this proven platform. Holding genuine 1756-L1 units in inventory allows maintenance teams to restore failed processors in minutes, preserve ladder program compatibility, and protect the substantial investment embodied in existing ControlLogix control infrastructure.iqelectro.com
Technical Specifications
| Parameter Name | Parameter Value |
|---|---|
| Product Model | 1756-L1 |
| Manufacturer | Allen-Bradley (Rockwell Automation) |
| Product Type | ControlLogix Programmable Automation Controller (PAC) |
| Series / Architecture | Logix5550 (ControlLogix 5550) |
| User Memory | 64 KB |
| Program / Data Type | Tag-based memory (no traditional data-file addressing) |
| Supported Languages | Ladder Diagram (LD), Function Block (FBD), Sequential Function Chart (SFC), Structured Text (ST) — IEC 61131-3 |
| Embedded Serial Port | 1 × RS-232 (DF1 / DH-485 protocol), RJ45-style 1756-CP3 cable |
| Network Compatibility (via modules) | EtherNet/IP, ControlNet, DeviceNet, DH+, Remote I/O |
| Maximum Connections | 250 |
| Maximum Discrete I/O | 128,000 points |
| Maximum Analog I/O | 4,000 points |
| Chassis Compatibility | 1756-A4, 1756-A7, 1756-A10, 1756-A13, 1756-A17 (any slot) |
| Memory Board Options | 1756-M1, 1756-M2, 1756-M3 (purchased separately) |
| Battery Backup | 1756-BA1 / 1756-BA2 (1 per controller) |
| Programming Software | RSLogix 5000 / Studio 5000 Logix Designer |
| Programming Cable | 1756-CP3 |
| Backplane Current | 120 mA @ 5V DC; 2 mA @ 24V DC |
| Power Dissipation | 4.1 W maximum @ 60 °C |
| Isolation Voltage | 30V continuous |
| Slot Width | 1 ControlLogix slot |
| Enclosure Type Rating | None (open-style) — ControlLogix chassis mounted |
| Operating Temperature | 0 °C to 60 °C (32 °F to 140 °F) |
| Storage Temperature | –40 °C to 85 °C (–40 °F to 185 °F) |
| Relative Humidity | 5% to 95% non-condensing |
| Vibration / Shock | 2 G @ 10–500 Hz vibration; 30 G operating / 50 G non-operating shock |
| Front Panel | Status and I/O indicator LEDs, keyswitch (Run / Prog / Remote) |
| Certifications | UL Listed, c-UL-us, CE, Class I Div 2 (Groups A, B, C, D), ATEX |
| Country of Origin | United States of America |
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