634 Fieldbus control through a fieldbus adapter
Control word and Status word
The Control word is the principal means for controlling the drive from a fieldbus
system. It is sent by the fieldbus master station to the drive through the adapter
module. The drive switches between its states according to the bit-coded instructions
in the Control word, and returns status information to the master in the Status word.
For the ABB Drives communication profile, the contents of the Control word and the
Status word are detailed on pages 637 and 638 respectively. The drive states are
presented in the state diagram (page 639).
When a transparent communication profile is selected eg. by parameter group 51
FBA A settings, the control word received from the PLC is available in 06.03 FBA A
transparent control word. The individual bits of the word can then be used for drive
control through bit pointer parameters. The source of the status word, for example
06.50 User status word 1, can be selected in 50.09 FBA A SW transparent source.
Debugging the network words
If parameter 50.12 FBA A debug mode is set to Fast, the Control word received from
the fieldbus is shown by parameter 50.13 FBA A control word, and the Status word
transmitted to the fieldbus network by 50.16 FBA A status word. This “raw” data is
very useful to determine if the fieldbus master is transmitting the correct data before
handing control to the fieldbus network.
References
References are 16-bit words containing a sign bit and a 15-bit integer. A negative
reference (indicating reversed direction of rotation) is formed by calculating the two’s
complement from the corresponding positive reference.
ABB drives can receive control information from multiple sources including analog
and digital inputs, the drive control panel and a fieldbus adapter module. In order to
have the drive controlled through the fieldbus, the module must be defined as the
source for control information such as reference. This is done using the source
selection parameters in groups 22 Speed reference selection, 26 Torque reference
chain and 28 Frequency reference chain.
Debugging the network words
If parameter 50.12 FBA A debug mode is set to Fast, the references received from
the fieldbus are displayed by 50.14 FBA A reference 1 and 50.15 FBA A reference 2.
Scaling of references
Note: The scalings described below are for the ABB Drives communication profile.
Fieldbus-specific communication profiles may use different scalings. For more
information, see the manual of the fieldbus adapter.
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