User manual

46 Publication 1756-RM093F-EN-P - January 2010
Chapter 5 Characteristics of Safety Tags, the Safety Task, and Safety Programs
SIL 2 Input Data
Keep channel A and channel B
input data separate at all times.
This example illustrates one
method for separating channel A
and channel B data in your
application. Any logic processing
that needs to occur must follow
ControlLogix SIL 2 guidelines.
Transferring SIL 2 Data Into the Safety Task
To transfer channel A and channel B SIL 2 safety data into the
GuardLogix safety task, use the safety tag mapping functionality in
RSLogix 5000 software. The tag names used here are for example
purposes. Implement and follow naming conventions that are
appropriate for your application.
Safety Functions Within the 1756 GuardLogix Safety Task
Follow these guidelines for using SIL 2 and SIL 3 safety functions
within the safety task:
• All available safety application instructions may be used.
• SIL 3 safety input modules (that is , Guard I/O modules) may be
used with single-channel configuration for SIL 2 safety functions.
• Use of the safety task signature and safety-locking the
application is recommended.
IMPORTANT
Do not perform safety-specific functions within these routines.
Safety evaluation must be handled within the 1756 GuardLogix
safety task.
TIP
To use the safety tag mapping feature, choose Map Safety Tags
from the Logic menu in RSLogix 5000 software.
IMPORTANT
You must not use SIL 2 data to directly control a SIL 3
output.