Normal Fieldbus Communication - Vacon optea Installation Manual

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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.
IO Data
High
Cyclic
Priority
x ms
Acyclic
Low
Priority
Parameters,
etc.
16
Appendix 6 - Fieldbus option board communication
= +
t t t
IOdatacycle updateinterval
= 4ms + 10ms
t
Update
interval
10ms
Software
Option Board
Figure 55. Normal fieldbus communication
Local contacts: https://www.danfoss.com/en/contact-us/contacts-list/
⋅
+ 2 t +
t
communicationdelay applicationcycle
( 2 5 ⋅ )ms
+ + 10ms = 34ms
SPI SPI
5ms 5ms
Drive Control Board
Process
Data
Application
task
1-50ms
Service
10ms
Data
Application
task
50-500ms
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