Vacon optea - Normal Fieldbus Communication

16
vacon • 248 Appendix 6 - Fieldbus option board communication
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16.3 Normal fieldbus communication
The normal fieldbus communication between option board and the AC drive application is visible in
Figure 55. In normal communication both process data and service data are transferred in
succession at 5 ms interval.
Communication delay for process data can be calculated by summing all delays together:
Example: With fieldbus cycle time of 4 ms and application cycle of 10 ms, the delay is:
NOTE: This value does not include delays of the fieldbus master, jitter in the process data cycle of
the communication protocol or resending due to electronic interference.
Figure 55. Normal fieldbus communication
tt
IOdatacycle
t
updateinterval
2 t
communicationdelay
t
applicationcycle
+⋅++=
t 4ms 10ms 25⋅()ms 10ms 34ms=++ +=
IO Data
Cyclic
x ms
Acyclic
Parameters,
etc.
Low
Priority
High
Priority
Software
10ms
10ms
Update
interval
SPI
5ms
SPI
5ms
Application
task
1-50ms
Process
Data
Application
task
50-500ms
Service
Data
Option Board Drive Control Board
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