Siemens SIMATIC S7-1500 Function Manual page 22

The backplane bus transports the input data to the CPU. The application is started
synchronized to the cycle. That is, the isochronous mode interrupt OB is called after a
configurable delay time T
the process response and provides the output data in time for the start of the next data cycle.
The length of the data cycle (send clock) is always configured by you.
Within time T
● Transported to the I/O module over the backplane bus
● Processed in the I/O module, e.g. converted to an analog value
After expiration of time T
Time T
STEP 7. STEP 7 automatically calculates a common, minimum T
Isochronous mode
Function Manual, 10/2018, A5E43884988-AA
4.2 Time sequence of synchronization in the central configuration
. The user program in the isochronous mode interrupt OB defines
V
, the data is:
O
, the data is output to the process.
O
can be configured by STEP 7 or by you. Let time T
O
Time sequence of synchronization
be assigned automatically by
O
.
O
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