4.3.4 How to plan the macrocycle
A macro cycle lasts for a number of bus clock cycles. The duration of the cyclic communication
depends on the configured hardware. You can define the time for a macro cycle and the
percentage of acyclic communication. The FF specifications recommend that at least 50% of
the bus time is kept free for acyclic communication.
For additional information, refer to the section "Nodes in the FOUNDATION Fieldbus
(Page 17)".
"Macrocycle" tab
Whether the configuration is consistent is determined on the basis of the output values and
the required interconnections. The result is displayed graphically.
"Calculate Schedule" button"
● Click this button to calculate the time for cyclic communication.
"Optimize macro cycle" button
● Click this button to set the macro cycle as follows:
Depending on the cyclical component (depending on the configured hardware), a minimum
macro cycle is set with a specified acyclical percentage.
Graphical display
Before downloading, click the "Calculate schedule" button. With the help of the display you
can check whether the configuration is consistent. The result is displayed graphically.
Display from left to right:
● Left area
The colored area on the left side indicates the percentage of acyclic communication.
● Left thin dividing line (50% of the bus load)
The lower limit of the percentage of acyclic communication of the bus load recommended
in the FF specifications.
● Thick dividing line
The limiting value set in the entry field "Percentage of acyclic communication".
● Right thin dividing line (70% of the bus load)
The upper limit of the percentage of acyclic communication of the bus load recommended
in the FF specifications.
● Right area
The colored area on the right side indicates the percentage of cyclic communication.
Meaning of the colored areas
● Yellow
Percentage of acyclic communication
● Dark green
Percentage of cyclic communication Configuration is free from errors.
Engineering
4.3 Parameter assignment
FOUNDATION Fieldbus
42 Commissioning Manual, 03/2013, A5E03880935-02
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