SKU: 1756-L55M22

Allen-Bradley 1756-L55M22 ControlLogix Controller

The Allen-Bradley 1756-L55M22 is a 750 KB ControlLogix Controller. Brand New, Original Stock, Global Shipping available for automated industrial platforms.

The Allen-Bradley 1756-L55M22, also cataloged as the 1756-L55M22 ControlLogix Controller, operates as a dedicated hardware component for application logic execution and backplane data exchange within ControlLogix 5555 system platforms. The unit features a dual-CPU architecture comprising a Logix processing unit for application code execution and a dedicated backplane CPU to handle I/O data communication and synchronization across the chassis.

Hardware Specifications

Parameter	Specification
Model	1756-L55M22
Brand	Allen-Bradley
Origin	USA
Weight	0.36 kg
Dimensions	14.35 x 14.0 x 14.5 cm
Operating Temp	0 to 60 deg C
Power Consumption	1.25 A at 5.1 VDC; 0.014 A at 24 VDC
User Memory (Logic/Data)	750 KB
Dedicated I/O Memory	208 KB
Local I/O Capacity	250 words
System Platform	ControlLogix / GuardLogix
Comm Port	Serial RS-232 (via 1756-CP3)
Battery Type	1756-BA1 / 1756-BATM

Backplane Bus Communication Velocity and Network Determinism

The 1756-L55M22 implements a hardware-based multitasking architecture to prioritize backplane bus communication velocity and logic synchronization. The internal backplane processor acts independently of the main execution core, ensuring that deterministic networks like EtherNet/IP, ControlNet, and DeviceNet maintain stable request-response intervals irrespective of application code complexity. It natively supports produced/consumed tag allocation, enforcing strict update times across distributed network nodes via continuous backplane data scanning. Firmware flash compatibility determines the maximum instruction set capability, requiring alignment between the controller hardware revision and the RSLogix 5000 programming environment.

Frequently Asked Questions

Q: How does the dual-CPU architecture impact the local backplane execution time?

A: The main Logix CPU processes the application program tasks sequentially, while the secondary backplane CPU handles communication cycles and diagnostic polling. This separation isolates user program execution from variable network communication loads, preventing interruptions in routine execution times.

Q: What is the behavior of the onboard diagnostic indicators during an active I/O fault?

A: The controller features a front-panel I/O LED indicator. An active fault or communication loss with designated I/O modules causes the green I/O LED to flash, prompting the execution of the system fault handler to capture diagnostics.

Q: What are the backup runtime restrictions during power deprivation cycles?

A: Non-volatile data retention is dependent on the external battery assembly (1756-BA1 or 1756-BATM). Without operational battery power, volatile RAM memory containing the logic application and runtime tags will clear upon a complete loss of chassis backplane power.

Field Installation Guidelines

Chassis Insertion and Torque Verification: Ensure that the chassis power supply is completely de-energized prior to inserting the controller into the slot. Align the circuit board with the top and bottom chassis guides and push firmly until the module retention tabs click into position.
Serial Port Shielding and Grounding: When utilizing the RS-232 serial interface via a 1756-CP3 cable for local industrial configuration, route the cable away from high-voltage AC lines or variable frequency drive cables to eliminate electro-magnetic interference.
Battery Module Connection: Connect the physical lead of the 1756-BA1 battery into the keyed socket inside the controller housing before putting the system into operational mode. Maintain a scheduled preventive maintenance replacement cycle based on ambient operating temperatures.