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Fundamentals of PROFIBUS
Operation manual
5
In contrast to cyclic communication, acyclic communication data are only
exchanged when necessary. Acyclic communication is performed either via an
appropriate routine within cyclic communication (for PKW routine, see
PROFIDrive profile version 2) or via the DP-V1 routines READ and WRITE. This
permits the connection of commissioning tools as class-2 master (C2) to
PROFIBUS.
Several acyclic channels are available at the same time. The C1 master (the
controller) maintains a continuously open connection to the inverter (MSAC1)
which can be used as necessary by the controller program (arrow 2). In addition,
the inverter provides the capacity for two connections (MSAC2) which can be
established and used as necessary by C2 masters (e.g., an operator panel or a
service PC).
Time wise on PROFIBUS, the cyclic data always have the highest priority. During
each data exchange cycle, the master inserts an acyclic telegram when
necessary. This does not noticeably affect the speed of PROFIBUS.
5.3.2 User data communication
The process data channel is used for high-speed transmission of data which are
used for controlling and monitoring the running process and which require a
particularly short transmission time. When the bus system is configured, the
selection of the PPO type specifies whether the cyclic parameter channel is to be
used and how many bytes the process data channel will have.
All parameters can be read and changed with the parameter channels. First, the
PKW1 routine (which uses the acyclic services of PROFIBUS) specified by
PROFIDrive version 3 is available and, second, the old PKW0 routine (which is
embedded in the cyclic data) defined by PROFIDrive version 2 is offered.
Because of the comprehensive capabilities and the access to all inverter
parameters without exception, the new PKW1 routine should be used if possible:
Transmission Channel Inverter with Option DP-V1 5000
Process data reference values
from the bus to the processing on
the device.
Complete processing of a PKW0
service.
PKW1 via acyclic services.
Depends on the configuration and setting of
the parameter A150 cycle time.
Approx. 16 to 64 ms
Depends on the configuration!
Approx. 16 to 64 ms
Depends on the configuration!
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ID 441687.03
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