Rockwell Automation Publication 843ES-UM001A-EN-P - February 2020 89
Appendix D
Use of Controller-based Safety Functions with
the 843ES CIP Safety Encoder
SFX Instruction
The Safety Feedback Interface (SFX) instruction scales feedback position into
position units and feedback velocity into speed units per unit of time. Feedback
position and velocity are read from the safety input assembly and become inputs
to the instruction. The SFX instruction also sets a reference position from a
home input and performs position unwind in rotary applications.
The 843ES CIP Safety encoder provides safe position and velocity feedback,
which can achieve up to and including SIL 3 PL e safety rating.
The outputs of the SFX instruction are used as inputs to other Drive Safety
instructions. For any drive that can perform a STO, to execute a controller-based
safety function, an SFX instruction is required. Although the SFX instruction is
a safety instruction, it alone does not perform a safety function.
In Figure 16
, the Safely limited Speed (SLS) instruction uses the Actual Speed
output from the SFX instruction during execution of the SLS safety function.
Figure 16 - SFX Instruction Feeds Data to SS1 Instruction
843ES
CIP Safety
Encoder
Feedback Position
(counts)
Feedback Velocity
(feedback units/second)
Actual Position
(position units)
Actual Speed
(position units/second
or position units/minute)
IMPORTANT Perform I/O verification and validation before validating your safety ladder
program. SFX instruction must be verified within your application.
When possible, use immediate operands for instructions to reduce the
possibility of systematic errors in your ladder program.
Instruction operands must be verified for your safety ladder program.
To Next Page
Loading...
Need help?
General
