Siemens SIMATIC S7-1500 Function Manual page 21

Time sequence of synchronization
4.2 Time sequence of synchronization in the central configuration
From reading-in of input data to outputting of output data
The basic time sequence of all components involved in synchronization is explained in the
following:
①
Measured value acquisition in the process
②
Isochronous read-in of input data from the central I/O
③
Transport of input data to the CPU
④
Further processing in the isochronous application of the CPU
⑤
Transport of output data to the central I/O
⑥
Isochronous output of output data
T_DC Data cycle (Time_DataCycle)
T Time for reading in the input data
I
T Time for outputting the output data
O
T Configured delay time
V
Figure 4-2 Time sequence of synchronization in the central configuration
So that all input data is ready for transport to the CPU at the next start of the cycle, the start
of the I/O read-in cycle is advanced by the amount of lead time T
inputs. After that, all synchronized inputs are read in. T
for analog-to-digital conversion and the like. The lead time T
or by you. Let the lead time T
STEP 7 ensures that a common, minimum T
20
be assigned automatically by STEP 7. With the default setting,
I
is set.
I
. T is the "flashbulb" for the
I I
is necessary in order to compensate
I
can be configured by STEP 7
I
Function Manual, 10/2018, A5E43884988-AA
Isochronous mode