User manual

24 Publication 1756-RM093F-EN-P - January 2010
Chapter 2 GuardLogix Controller System
Primary Controller
The primary controller is the processor that performs standard and
safety control functions and communicates with the safety partner for
safety-related functions in the GuardLogix control system. The primary
controller consists of a central processor, I/O interface, and memory.
Safety Partner
To satisfy SIL 3 requirements, a safety partner, catalog number
1756-LSP, must be installed in the slot immediately to the right of the
primary controller. The safety partner is a co-processor that provides
redundancy for safety-related functions in the system.
The safety partner is configured by the primary controller. Only a
single download of the user program to the primary controller is
required. The safety partner’s operating mode is controlled by the
primary controller.
Chassis
The 1756-Axx chassis provides the physical connections between
modules and the 1756 GuardLogix system. Any failure, though
unlikely, would be detected as a failure by one or more of the active
components of the system. Therefore, the chassis is not relevant to the
safety discussion.
Power Supplies
These ControlLogix power supplies are suitable for use in SIL 3
applications:
• 1756-PA72 ac power supply
• 1756-PA75 ac power supply
• 1756-PB72 dc power supply
• 1756-PB75 dc power supply
• 1756-PA75R ac power supply (redundant)
• 1756-PB75R dc power supply (redundant)
• 1756-PSCA or 1756-PSCA2 redundant power-supply chassis
adapter (required for use with redundant power supplies)