How To Plan The Macrocycle - Siemens SIMATIC PCS 7 FOUNDATION Fieldbus Commissioning Manual

Schedule calculation canceled
If the schedule calculation could not be completed successfully, you receive an error message.
Check the settings of the bus parameters.
Note
Error message "Cancel Schedule Calculation: Error at bus parameter"
The error message "Cancel Schedule Calculation: Error at bus parameter" is issued by
SIMATIC PDM if there are too many configured interconnections.
You can find additional information about this in the section "Additional notes on
configuration (Page 34)".
Checking the bus parameters
1. In the "Properties - Foundation Fieldbus" dialog box, select the "Bus parameters" tab.
2. In the "Bus parameters" area, select the "Automatic calculation" radio button.
The default values are set.
3. Switch to the "Macro cycle" tab.
4. Click "Calculate Schedule".
If your bus parameters deviate from the default values, you can adapt the values in the
input boxes ("Acyclical percentage" and "Macro cycle").
Run the schedule calculation every time you make a change.
Requirements for downloading
First, configure all interconnections.
If you have inserted new FF devices in the FF segment or want to use new parameters, online
changes are not possible.
If necessary, correct the macro cycle settings.
5.3.4

How to plan the macrocycle

A macrocycle 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 macrocycle and the
percentage of acyclic communication. The FF specification recommends that at least 50% of
the bus time be kept free for acyclic communication.
For additional information, refer to the section "Nodes in the FOUNDATION Fieldbus
(Page 21)".
"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.
FOUNDATION Fieldbus
Commissioning Manual, 02/2015, A5E32711026-AC
Engineering
5.3 Parameter assignment
49