Siemens SIMATIC ET 200AL, System Manual

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Response times
B.2 Response time parameters for the F-DI 4/F-DQ 2 digital inputs
Digital I/O module F-DI 4+F-DQ 2x24VDC/2A, 4xM12 (6ES7146-5FF00-0BA0)
84
Equipment Manual, V1.0, 05/2021, A5E51082342-AA
T
WCDT_i
= T
filter
+ T
sct
+ 2 x T
cycle
T
OFDT_i
= T
WCDT_i
+ T
scf
1oo2 evaluation:
T
WCDT_i
= T
filter
+ T
sct
+ 2 x T
cycle
T
OFDT_i
= T
WCDT_i
+ MAX (T
scf,
T
dis
)
Where:
T
cycle
Internal cycle time of the fail-safe module
T
dis
Discrepancy time:
•
Configured "Discrepancy time" for 1oo2 channels changing from "0" to "1"
• Configured "Discrepancy time" for 1oo2 channels changing from "1" to "0" and "Supply last valid value"
option configured for discrepancy behavior
• "0" for 1oo2 channels changing from "1" to "0" and "Supply value 0" option configured for discrepancy
behavior
You should include the expected discrepancy time between your sensor inputs in your external sensor
delay. Your configured T
dis
contributes to T
OFDT_i
as the time delay for the fail-safe module's digital in-
puts to passivate the channel due to fault case extension of the discrepancy time.
This parameter can be listed separately in the RT_calculator. Do not include T
dis
in the value of T
OFDT_i
that you enter into the RT_calculator if you enter T
dis
as a separate item.
T
filter
Configured "Input filters" time for the channel
T
OFDT_i
One Fault Delay Time: Maximum response time for the fail-safe module's digital input to report a channel
as passivated
T
scf
Time delay for short-circuit fault duration:
•
Configured "Interval for short-circuit test", when operating in high demand or continuous mode and
depending on the short-circuit test to achieve your required level of safety integrity
• "0" when not depending on the short-circuit test to achieve your required level of safety integrity
T
sct
Time delay for short-circuit test duration:
•
"0" if no short-circuit test configured
• "0" for 1oo2 channels changing from "1" to "0" and "Supply value 0" option configured for discrepancy
behavior
• "Duration of short-circuit test" + "Input filters" time if short-circuit test is configured
(Confirmation: "Input filters" can occur twice in equation for T
WCDT_i
if short-circuit test is configured.)
T
WCDT_i
Worst Case Delay Time: Maximum response time from a signal transition at the digital input to the reliable
availability of the safety message frame available for the fail-safe CPU request
The term "2 x T
cycle
" for "maximum response time of the fail-safe module" allows for other
input delays to complete just after the beginning of a cycle. The fail-safe module's digital
inputs process and report the changed input data on the next cycle.