Siemens SIMATIC ET 200AL - Program Processing According to the IPO Model with Application Cycle = 1

Functions
5.7 Isochronous mode
PROFINET with STEP 7 V15
202 Function Manual, 12/2017, A5E03444486-AH
The "SYNC_PI" and "SYNC_PO" instructions can update the process image partition only
within the permitted execution window. The execution window for the possible call of the
"SYNC_PI" and "SYNC_PO" instructions stretches from the end of the cyclical data
exchange on the PROFINET IO until the point in time before the end of T_DC at which the
outputs can still be copied on time. The data exchange must be started within this time
window. If the "SYNC_PI" and "SYNC_PO" instructions are not processed within the
execution window, the system functions will indicate this with a corresponding error
message. An image in which the execution window and the corresponding times are
displayed can be found in the next section.
Program execution models
Depending on the order of the "SYNC_PI" and "SYNC_PO instructions in OB6x and the
application cycle factor used, the program execution can be divided into two basic models:
●
IPO
model (read
I
nputs -
P
rocessing - write
O
utputs), CACF = 1
●
IPO
model (read
I
nputs -
P
rocessing - write
O
utputs), CACF > 1
5.7.6
Program processing according to the IPO model with application cycle = 1
Characteristics of the IPO-model with application cycle factor = 1
The IPO model with application cycle factor = 1 is characterized by the fact that the
execution of the I/O data is complete within one system clock cycle T_DC. The shortest
response times are achieved with this model.