Siemens SIMATIC Vision Sensor VS 130-2 Manual page 116

Process Interface
Step Activity in the DP Master or I/O Controller User Program
Last - 2 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 DP master.
Last - 1 Query byte 1 of the "Send" user data interface cyclically. As soon as the value 0 is read, go
to last step.
Last Acknowledge correct receipt of all data by writing the value 0 in byte 1 of the "Receive" user
data interface.
Response to Problems, Time-outs, and Errors
The processing unit monitors the following:
•
The time between the arrival of two acknowledgments from the DP master is
monitored for the time-out set in the Connect > Ports > DP > Timeout or
Connect > Ports > PNIO > Timeout menu.
•
The correct sequence of the acknowledged data packets of the DP master or
I/O controller is monitored.
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.
It is advisable to implement the following monitoring functions in the user program
of the DP master or I/O controller:
•
Monitoring of the time between arrival of two consecutive data packets.
•
Monitor the correct order of the data packets sent by the processing unit.
•
Check whether the total length of the user data actually transferred matches
the net total length of data to be transferred as specified by the processing unit
at the start of the data transfer.
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.
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Vision Sensor SIMATIC VS 130-2/VS 130-2vcr
A5E00475759-01