Operating instructions

4.6. Synchronize and Freeze

The control commands SYNC/UNSYNC and FREEZE/UNFREEZE are broadcast functions.

SYNC/UNSYNC is used to synchronize control commands and/or speed reference to all the con-

nected frequency converters.

FREEZE/UNFREEZE is used to freeze the status feedback in the slaves to get synchronized feed-

back from all connected slaves.

The synchronize and freeze commands affect only process data (the PCD part of the PPO).

4.6.1. SYNC/UNSYNC

SYNC/UNSYNC can be used to obtain simultaneous reactions in several slaves, for example

synchronized start, stop or speed change. A SYNC command will freeze the relevant control word

and speed reference. Incoming process data will be stored but not used until a new SYNC com-

mand or a UNSYNC command is received.

An UNSYNC command stops the synchronisation mechanism and enables normal DP data ex-

change.

4.6.2. FREEZE/UNFREEZE

FREEZE/UNFREEZE can be used for simultaneous reading of process data, for example output

current, from several slaves.

A FREEZE command will freeze the actual values and upon request the slave will send back the

value that was present when the FREEZE command was received.

Upon receipt of an UNFREEZE command the values will once again be continuously updated and

the slave will return a present value, i.e. a value generated by conditions at present time.

The values will be updated when a new FREEZE or UNFREEZE command is received.

VLT

Profibus 4. How to Control the Frequency Converter

MG.33.C4.02 - VLT

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