optris PROFIBUS-DP-V1, Руководство оператора

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4 PROFIBUS DP
Within PROFIBUS DP systems, the master (PLC, PC, etc.) generally communicates with many slaves (IO,
drive, etc.) whereas only the master can access the bus (sent unasked telegrams)
while a DP slave only
sends telegrams if it has been requested by a master.
4.1 DP startup
Before master and slave cyclically exchange data with each other, the parameter and configuration data are
transferred from the master to the slaves during the DP startup. After sending the parameter and
configuration data, the master interrogates the diagnostic data of the slave until the slave signals its
readiness for data exchange. Depending on the amount of calculations that the slave has to perform by
receiving parameter and configuration data until it is ready for data exchange, this may take several seconds.
The slave therefore has the following states:
4.1.1 Parameter data
The parameter data are sent from the master to the slaves with the SetPrmLock request telegram; the
SetPrmLock response telegram contains no data and therefore consists of only one byte, the short
acknowledgment. The parameter data consists of DP parameters (e.g. setting of the DP watchdog, checking
of the IdentNumber (unique for each DP device)), of DP-V1/DP-V2 parameters and of application-specific
parameters that occur only once during the startup must be transferred. If an error occurs in the parameter
data, this is indicated in the diagnostic data and the slave remains in the state WAIT-PRM.