Siemens SIMATIC VS120 Operating Instructions Manual page 141

Procedure
Step
1
2
3
4
5
6
...
Last - 4
Last - 3
Last - 2
Last - 1
Last
Response to problems, timeouts, and errors
The processing unit monitors the following:
• The time between the arrival of two acknowledgments from the DP master is monitored
• The correct sequence of the acknowledged data packets of the DP master or I/O
If an error occurs, the processing unit enters B#16#FF in byte 1 of the "Send" user data
interface and so aborts the current data transmission.
If an error occurs, writing B#16#FF to byte 1 of the "Receive" user data interface causes the
current data transmission to be aborted.
Vision Sensor SIMATIC VS120
Operating Instructions, Edition 02/2006, A5E00757507-01
Activity in the user program of the DP master or I/O controller
Poll byte 1 of the "Send" user data interface. As long as this byte has the value 0, there
is no new data. If it has the value 1, go to step 2.
The value 1 in byte 1 of the "Send" user data interface means: The SIMATIC VS120
has started data transmission.
Read 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 first data packet from bytes 5 to 31.
Acknowledge correct receipt of the first data packet by writing the value 1 in byte 1 of
the "Receive" user data interface.
The processing unit polls byte 1 of the "Receive" user data interface. 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 second data packet and enters the number of this data package (in this
case 2) in byte 1.
Poll byte 1 of the "Send" user data interface. As long as this still contains the number of
the previously transferred data packet (1), there is no new data. As soon as byte 1 has
the value 2 (number of the next data packet), go to step 5.
Read the user data of the second data packet from bytes 5 to 31.
Acknowledge correct receipt of the second data packet by writing the value 2 in byte 1
of the "Receive" user data interface.
...
Poll byte 1 of the "Send" user data interface. As long as this contains the number of the
last but one data packet, the data of the last data packet is not yet available. As soon
as byte 1 has the number of the last data packet, go to next step.
Read the user data of the last data packet from bytes 5 to 31.
Acknowledge receipt of the last data packet by writing the number of the last data
packet in byte 1 of the "Receive" user data interface.
The processing unit polls byte 1 of the "Receive" user data interface. 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 the
current data transfer to the PROFINET DP master.
Poll byte 1 of the "Send" user data interface. As soon as the value 0 is read, go to last
step.
Acknowledge correct receipt of all data by writing the value 0 in byte 1 of the "Receive"
user data interface.
for the time-out set in the Connect > Ports > DP > Timeout or Connect > Ports > PNIO >
Timeout menu.
controller is monitored.
Process interfacing over an automation system (PLC, PC)
10.4 Control over PROFIBUS DP and PROFINET IO
10-15