Description of the Software Modules and Parameters
Parameter manual
b maXX
BM5800
Document No.: 5.16029.03
207
3
3.4.11 Fieldbus communication
The fieldbus communication is realized via a separate processor. The basic configuration
is carried out by the fieldbus processor or by the fieldbus master, as well. Therefore, most
parameters within this range are provided for display and diagnostics. Specific settings
must be made in the controller.
It is necessary and also helpful to understand the communication timing in specific cases.
Basic sequence of the different software components in the controller
Figure 63:
Basic sequence of the fieldbus task (fieldbus cycle 1ms, RT0 cycle 250 µs)
The basic sequence of the relevant software components for the fieldbus communication
is shown in
. The current controller responds every 62.5 µs. The position and
speed controller responds every 250 µs right before the current controller responds. The
fieldbus communication takes place in an own task, which can be interrupted by the cur-
rent controller or by the position and speed controller.
The beginning of the fieldbus task or of the controller interrupt (after this the fieldbus task
starts) is synchronized to the sync signal of the fieldbus. Hence, the fieldbus task starts
at a sync offset of 0 µs with a time delay of about 30 µs shortly after the sync signal. This
is due to the computing time of the controller interrupt.
In a fieldbus task the set values are read, the actual values are written and then the inter-
polation for the cyclical position set value specification is calculated. The interpolated po-
sition set values are transferred to the position controller with the next position/speed
controller cycle (RT0 cycle).
Transferring the set values from the fieldbus task into the position/speed
controller.
At 250 µs cycle time or greater the set values are transferred in the next RT0 cycle after
the fieldbus task was started.
At 125 µs cycle time the set values are transferred in the RT0 cycle after next one, so that
the fieldbus task is available of more computing time.
