Configuring Hardware and Communication Connections STEP 7.pdf

Configuring the Distributed I/O (DP)
Optimizing the Configuration
To assist you in optimizing the configuration, the "Isochrone Mode" dialog box
provides an overview of all clocking-related parameters. To open this dialog box,
go to HW Config and select the Edit > Isochrone Mode menu command.
The dialog box is divided into a hierarchy containing "PROFIBUS", "Slave" and
"Module" display areas. When you select a master system in the "PROFIBUS"
area, the "Slave" area will automatically display the associated slaves. Similarly,
when you select a DP slave, the "Module" area will automatically display the
associated modules. For a detailed description of the columns displayed in the
dialog box, see the relevant online help section.
Creating a User Program
Create the required synchronous cycle interrupt OBs (i.e. OB 61).
At the start of the synchronous cycle interrupt OBs, the SFC 126 'SYNC_PI' must
be called to update the process image partition for inputs, and at the end of OB 61,
SFC 127 'SYNC_PO' must be called to update the process image partition for
outputs. The process image partition to be used here is the one configured in the
CPU ("Synchronous Cycle Interrupts" tab).
Notes
In particular, the following situation can arise with very short DP cycle times: The
runtime of the user program (OB6x with SFC 126/127 called) is greater than the
smallest cycle (see the technical data for the CPU, Section "Isochrone Mode"). In
this case, you will have manually increase the DP cycle time that was automatically
calculated by STEP 7.
The runtime for individual OBs can be determined for different periods of time with
SFC 78 'OB_RT' (WinAC RTX only).
Configuring Hardware and Communication Connections with STEP 7
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