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Process interfacing via an automation system (PLC, PC)
10.4 Control with FB79
Step
Activity in the user program of the PROFINET IO controller
1
Scan byte 1 of the "Send" user data interface cyclically. As long as this byte has the value 0, there is no
new data available. If it has the value 1, go to step 2.
2
The value 1 in byte 1 of the "Send" user data interface has the following meaning: The reader has started
data transfer.
Read out the net total length of the data to be transferred from bytes 2 and 3 of the "Send" user data
interface and the user data of the 1st data packet from bytes 5 to 31.
3
Acknowledge correct receipt of the 1st data packet by writing the value 1 to byte 1 of the "Receive" user
data interface.
The reader scans byte 1 of the " Receive" user data interface cyclically. As soon as it reads the value 1, it
fills bytes 5 to 31 of the "Send" user data interface with the user data of the 2nd data packet and enters the
number of this data packet (in this case 2) in byte 1.
4
Scan byte 1 of the "Send" user data interface cyclically. As long as this byte contains the number of the
previously transferred data packet (1), there is no new data available. As soon as byte 1 has the value 2
(number of the next data packet), go to step 5.
5
Read the user data of the 2nd data packet from bytes 5 to 31.
6
Acknowledge correct receipt of the 2nd data packet by writing the value 2 to byte 1 of the "Receive" user
data interface.
...
...
Last - 4
Scan byte 1 of the "Send" user data interface cyclically. As long as byte 1 contains the number of the
second last data packet, the data of the last data packet is not yet available. As soon as byte 1 contains
the number of the last data packet, go to the next step.
Last - 3
Read the user data of the last data packet from bytes 5 to 31.
Last - 2
Acknowledge receipt of the last data packet by writing the number of the last data packet to byte 1 of the
"Receive" user data interface.
The reader scans byte 1 of the " Receive" user data interface cyclically. As soon as it reads the number of
the last data packet, it writes the value 0 to bytes 2 and 3 of the user data interface and also to byte 1. The
value 0 in byte 1 signals the end of data transfer to the I/O controller.
Last -1
Scan byte 1 of the "Send" user data interface cyclically. As soon as you read the value 0, go to the last
step.
Last
Acknowledge correct receipt of all the data by writing the value 0 to byte 1 of the "Receive" user data
interface.
278
SIMATIC MV420 / SIMATIC MV440
Operating Instructions, 04/2013, A5E02371045-06
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