Appendix 6 - Fieldbus option board communication
vacon • 249
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16
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):
t
=
t
IOdata cycle
+
t
update interval
+
t
application cycle
Example: With fieldbus cycle time of 1 ms an application cycle of 1 ms the delay is::
t
=1 ms + 1 + 1 ms = 3 ms
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 56. Fast fieldbus communication
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
®
NXP drives
is undesirable.
NOTE:
This mode is automatically enabled in VACON
®
Applications supporting 16 process data
items.
IO Data
Cyclic
x ms
Acyclic
Parameters,
etc.
Low
Priority
High
Priority
Software
Option Board
Drive Control Board
SPI
1ms
SPI
1ms
Application
task
1-50ms
Process
Data
Application
task
50-500ms
Service
Data
11723_uk
UART
Acyclic
Содержание OPTE9
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