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Entry type: FAQ Entry ID: 7769498, Entry date: 08/13/2008

MICROMASTER 4 (MM4): Using DriveMonitor after an AOP

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This FAQ applies to MICROMASTER 4 (MM4)

After I have used an AOP, why can I no longer go online with my frequency inverter via a BOP link with Drive Monitor?

The AOP sets the PZD length for the BOP link to 4. However Drive Monitor by default uses a PZD word length of 2.

The PZD is part of the data message used to transmit information between the drive and AOP or PC.

Therefore, if Drive Monitor is used after an AOP, the online connection can no longer be established with the frequency inverter via a BOP link.

This can be simply resolved in the following ways:

  • The simplest solution is as follows: Do a power cycle (ON/OFF/ON), as the AOP only writes the value of the PZD word length for the BOP link (parameter P2012[1] USS PZD length, serial interface BOP link) to the RAM of the drive. This is the reason that P2012[1] is reset to 2 for a switching operation.
    However, this solution can only be used if data was not saved from RAM to EEPROM (using P0971) using the AOP - and if the parameter settings in the frequency inverter RAM are of no significance and can be reset to the factory setting as a result of the switching operation.

  • If this is not the case, then the PZD word length in Drive Monitor must be changed to 4. In Drive Monitor, go to “Drive properties” (File > Drive properties) and set the PZD length to 4 (refer to Fig. 1). In Drive Monitor an online connection with the frequency inverter can now be established via the BOP link.

    Fig. 1 – Changing the PZD word length

  • An additional way of setting parameter P2012[1] to 2 is to use a BOP. Insert a BOP into the frequency inverter and change the setting of parameter P2012[1] to 2.

  • It is also possible to go online with the frequency inverter via PROFIBUS in STARTER or via the COM-Link in Drive Monitor or STARTER. Parameter P2012[1] can then be changed to 2.


You require a MICROMASTER PROFIBUS option module to establish the PROFIBUS connection with the frequency inverter.

Please note the following:
When using an AOP the Baud rate settings should also be checked - see FAQ MM4: AOP settings for reliable communication for correct settings. ID: 10556575

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