NORD Drivesystems BU0020 - Manual (Page 50)

PROFIBUS DP – Supplementary manual options for NORD - Frequency Inverters
50 BU 0020 GB-2612
As the NORD components /PROFIBUS technology units described in this manual do not support DP-
V2 functions, their functionality is not described in further detail in this section.
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5.3 FREEZE and SYNC mode
In addition to the automatic participant-related transfer of reference data, DPM1 masters can also
simultaneously sent some control commands to the bus participants for synchronisation of the DP
slaves. These control commands are sent as multicast (transfer of messages from a point to a group).
The following only lists and describes some of the operating modes/control commands. Detailed
information about the basic functionalities is explained in the relevant specialist PROFIBUS DP books.
Control command FREEZE
The PROFIBUS master sends a FREEZE control command to one or a group of DP slaves
(PROFIBUS technology unit), which in turn commence the FREEZE mode. On receipt of the FREEZE
command, the actual value (actual status) of all addressed technology units (DP slaves) is "frozen". In
the next Profibus cycle, the "frozen" data are cyclically transferred to the PROFIBUS master. After
each further FREEZE control command sent from the master, the DP slaves once again "freeze" their
statuses. The input data is only updated if the master has sent the next FREEZE control command.
The actual values are enabled again via an UNFREEZE command sent from the master and from the
DP slaves to the PROFIBUS master, so that changes can be transferred in each cycle and FREEZE
mode terminated.
Control command SYNC
The PROFIBUS master sends a SYNC control command to one or a group of DP slaves (PROFIBUS
technology unit), which in turn commence the SYNC mode. On receipt of the SYNC command, the
setpoint values of all addressed technology units (DP slaves) is "frozen". With the following transfer of
reference data the output data in the DP slaves is saved, but the output statuses remain unchanged.
The saved output data is only switched to the outputs on receipt of the next SYNC control command.
In the following cycle, the master sends an UNSYNC command and the setpoint values are adopted
simultaneously by all the bus participants which are addressed and SYNC mode is terminated.
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5.4 Protection mechanisms
For safety reasons, PROFIBUS DP is equipped with effective protective functions against failure of the
transfer devices and incorrect parameterisation. Monitoring mechanisms are implemented in both the
DP master and the DP slaves in the form of time monitoring, by means of access monitoring intervals
(times), which can be specified during planning.
Access monitoring
If there is no communication with a DP slave via the PROFIBUS master (DP standard protocol) within
a time interval which can be parameterised, all the outputs of the affected technology unit are set to
"0" and all connected frequency inverters are set to error status. This is also known as the so-called
safe condition, which is automatically adopted by each DP slave if there is no transfer of data within
the access monitoring interval. Parallel to this, the user is informed of the fault status of the data
communication via a diagnostic alarm or the LED status indicator. The access monitoring serves as a
protective function against incorrect parameterisation or failure of the transfer facilities and can by
explicitly enabled or disabled for each individual DP slave.