1756-L73 is a ControlLogix 5570 controller with 8 MB of user memory and 0.98 MB of I/O memory. It installs in a 1756 ControlLogix chassis and communicates with plant networks through separate chassis communication modules.

The controller includes one USB client port for programming and service activity. A Secure Digital card can provide nonvolatile storage, while supported system architectures include standard and redundant controller configurations with the appropriate hardware and firmware.

Manufacturer	Rockwell Automation
Brand	Allen-Bradley
Product Family	ControlLogix 5570
Catalog Number	1756-L73
Controller Memory	8 MB
I/O Memory	0.98 MB
Nonvolatile Memory	Secure Digital card option
USB Ports	1 client port
Embedded Network Port	None
Maximum Controller Connections	500
Chassis Current at 1.2 V DC	5 mA
Chassis Current at 5.1 V DC	800 mA
Power Dissipation	2.5 W
Communication Context	EtherNet/IP, ControlNet, DeviceNet, Data Highway Plus, Remote I/O, SynchLink and USB through supported modules
Redundancy	Supported with the specified redundancy system
Lifecycle	Active Mature

• Executes Logix control applications with 8 MB user memory.
• Manages as many as 500 controller connections in a designed ControlLogix architecture.
• Uses chassis communication modules instead of an embedded industrial network port.
• Provides a front USB client connection for local programming and maintenance.
• Supports a Secure Digital card for nonvolatile project storage.
• Can participate in a ControlLogix redundancy solution when all system requirements are met.

• Installs in a compatible 1756 ControlLogix chassis with an adequate chassis power supply.
• Network communication requires the appropriate 1756 communication module for the installed protocol.
• The Studio 5000 project, controller firmware major revision and electronic keying must align.
• Redundant use requires matched partner hardware, redundancy modules, firmware and qualified chassis configuration.
• I/O tree size, produced and consumed tags, motion resources and controller connections must be reviewed before substitution.

• 1756-L73 is classified as Active Mature and remains relevant to existing ControlLogix 5570 installations.
• A service exchange should use the same controller catalog number and a compatible firmware revision unless the project is intentionally upgraded.
• Save the ACD project, firmware version, Secure Digital image, chassis inventory and network configuration before removal.
• A move to a newer ControlLogix controller requires review of firmware, software, communication modules, redundancy and application resources.
• Perform a controlled startup and verify I/O, communications, safety interfaces, motion and produced or consumed data after replacement.

How much user memory does 1756-L73 provide?

The controller provides 8 MB of user memory plus 0.98 MB reserved for I/O data.

Does the controller have an embedded EtherNet/IP port?

No. Industrial network access is provided through supported communication modules in the ControlLogix chassis.

What is the USB port used for?

The USB client port supports local programming and service communication.

Can 1756-L73 operate in a redundant pair?

Yes, when it is used with the specified redundancy hardware, matched firmware and a qualified system configuration.

How many controller connections are supported?

The published controller capacity is up to 500 connections.

What should be archived before an exchange?

Archive the ACD project, firmware, SD-card image, network modules, chassis slot map and all application dependencies.