Fast Fieldbus Communication; Normal Extended Mode - Vacon optea Installation Manual

Appendix 6 - Fieldbus option board communication
16.4

Fast fieldbus communication

The fast mode decreases the communication delay between the PLC and the AC drive application
significantly by using two communication channels separately for process and service data. The
process data interval is set to 1 ms, while other data is sent acyclically. When the fast mode is
activated, the application can be synchronized to run with the communication cycle. The Fast
communication mode is visible in Figure 56. This mode also includes the ability to transfer 16
process data items.
The communication delay for process data in fast communication mode is (when application task is
synchronized with communication):
Example: With fieldbus cycle time of 1 ms an application cycle of 1 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
Software
Acyclic
Low
Priority
Parameters,
etc.
16.5

Normal Extended Mode

The normal extended mode uses the same communication method that is used in "Fast mode", but
reduces the communication cycle to 10 ms.
This mode can be used in applications where 16 process data items are required but lowest possible
communication delay is not needed or the increased CPU load of Fast mode to VACON
is undesirable.
NOTE: This mode is automatically enabled in VACON
items.
Local contacts: https://www.danfoss.com/en/contact-us/contacts-list/
t = t + t
IOdata cycle update interval
t =1 ms + 1 + 1 ms = 3 ms
Option Board
Figure 56. Fast fieldbus communication
+ t
application cycle
SPI SPI
1ms 1ms
UART
Acyclic
Drive Control Board
®
Applications supporting 16 process data
vacon • 249
Process
Data
Application
task
1-50ms
Service
Data
Application
task
50-500ms
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®
NXP drives
16