Siemens SIMATIC ET 200AL System Manual page 2201

4.3.3 TIO_DI_ONCE: Reading in edges once at the digital input and associated time
stamps
Description
TIO_DI_ONCE detects the edges at a digital input of a TIO module once and returns the
associated time stamps. Alternatively, you can use this instruction to control a timer DI
channel that is configured as an edge-triggered enable for another channel.
Startup characteristics
During startup of the CPU, the instruction TIO_DI_ONCE applies the input parameters once
and checks the following:
● Checking HWID
● Checking to see if the number of the digital input (Channel) is in the permitted range
(depending on addressed module and channel configuration)
● Checking TIO_SYNC_Data.ERROR: Is an error present at TIO_SYNC?
● Checking TIO_SYNC_Data.TO_TIMES for plausibility (0 ms to 4 ms)
● Checking to see whether the OB is isochronous
If startup takes place without errors, the instruction changes to normal operation. In the event
of an error, the instruction does not change to normal operation and generates an error
message.
Functional description: Time stamp detection
In normal operation, the instruction detects the edges at a digital input and the associated
time stamps of the first valid, defined edge pair after the start of a read-in job. Use the input
parameter EdgeSel to determine the edges for which time stamps are detected. To detect a
new edge pair, a new positive edge is required at the REQ input parameter of the instruction.
You connect the input TIO_SYNC_Data with the output of the same name of the TIO_SYNC
instruction. This ensures a shared time basis.
High-precision input/output with Time-based IO
Function Manual, 11/2019, A5E33454822-AC
Programming
4.3 Time-based IO
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