Dynamic Frame Packing - Siemens SIMATIC ET 200AL System Manual

Functions
5.6 PROFINET with performance upgrade
5.6.1

Dynamic frame packing

Dynamic frame packing
Previously, individual PROFINET IO frames were sent for every PROFINET IO device.
The performance upgrade uses the dynamic frame packing procedure that is based on the
summation frame method. With the summation frame method, a frame contains the user
data for neighboring devices on a line. With Dynamic Frame Packing, every IO device takes
its data from the frame and forwards the rest. The frame is shortened from IO device to IO
device. Dynamic frame packing improves the use of the bandwidth in a line topology.
The following figure shows how Dynamic Frame Packing works based on the example of a
frame containing the user data for 3 IO devices.
①
②
③
④
⑤
⑥
Figure 5-55
DFP groups
Dynamic frame packing automatically groups IO devices that support the performance
upgrade into DFP groups. To be grouped together in a DFP group. the IO devices must be
located one after the other in a line and must have the same update time and watchdog time.
As soon as a maximum frame size for the DFP group is exceeded or a maximum number of
members for a DFP group is reached, Dynamic Frame Packing automatically opens a new
DFP group.
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The PROFINET IO frame contains the user data for all 3 IO devices (green, blue and orange).
The PROFINET IO frame reaches the first IO device. The IO device takes its user data (green)
from the frame and forwards the remaining frame.
The PROFINET IO frame contains the user data for two IO devices (blue and orange).
The PROFINET IO frame reaches the second IO device. The IO device takes its user data
(blue) from the frame and forwards the remaining frame.
The PROFINET IO frame contains the user data for one IO device (orange).
The PROFINET IO frame reaches the last IO device. The IO device saves the entire frame
including user data (orange).
Dynamic Frame Packing (DFP)
PROFINET with STEP 7 V15
Function Manual, 12/2017, A5E03444486-AH