Allen-Bradley 1756-LSP GuardLogix Safety Partner Controller

The Allen-Bradley 1756-LSP is a dedicated GuardLogix Safety Partner Controller belonging to the ControlLogix platform. This specialized hardware module functions exclusively as a co-processor alongside a primary GuardLogix controller (such as the 1756-L61S, 1756-L62S, or 1756-L63S) to establish a redundant, 1oo2 (One out of Two) voting safety architecture.

Hardware Specifications

Safety Architecture & Memory Structure

The 1756-LSP does not store or process independent user logic. It executes identical safety tasks in parallel with the primary safety controller. By performing cross-checking calculations on the safety data stream, the primary and partner module pair ensures fail-safe execution. This tightly coupled architecture enables the system to satisfy strict functional safety criteria up to SIL 3 (IEC 61508) and Performance Level e (PL e) / Category 4 (ISO 13849-1).

While the 1756-LSP houses internal tracking registers, it relies completely on the primary controller’s safety memory allocation. When paired with the 1756-L61S or 1756-L62S, it leverages 1 MB of safety memory, which expands to 3.75 MB when matched with a 1756-L63S processor.

Frequently Asked Questions

Q: Can the 1756-LSP be placed in a separate chassis from the primary safety controller?

A: No. To satisfy functional safety constraints, the 1756-LSP must be installed in the slot immediately adjacent (typically to the right) of the primary GuardLogix safety controller within the same local ControlLogix chassis.

Q: What happens if the 1756-LSP safety partner faults or is removed while running?

A: Because the architecture relies on 1oo2 voting verification to achieve SIL 3 compliance, a fault or removal of the safety partner will immediately drop the safety task into a configurable fail-safe state, typically disabling safety-related outputs across the control network.

Field Installation Guidelines

• Chassis Slot Assignment: Insert the 1756-LSP into the slot right next to the primary GuardLogix processor. Ensure the top and bottom chassis locking tabs click into place to secure backplane alignment.
• Firmware Synchronization: The major and minor firmware revision of the 1756-LSP must precisely match the firmware version installed on the companion primary controller. Discrepancies will prevent the controllers from establishing their safety link.
• Key Switch Manipulation: The safety partner does not possess a front-facing mode key switch. Operating states (RUN, PROG, REM) are driven entirely by turning the key switch located on the faceplate of the primary controller.