Lenze 3241C - Manual (Page 20)

3 API functions
18
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3.4.6 PDO communication
Process data (PDO)
In order to read process data from the backplane bus, the BpbReadPdo function is
used, reading the process input image. The process output image can be written to
the backplane bus by means of the BpbWritePdo function. The reading/writing of
PDOs is only possible in the Operational state.
Reading/writing the PDOs of a group is only transmitted from/to the BPB controller if
the group status is "RUNNING“. During the "INIT“ group status, the values are read as
0 (directly in the driver, not from the BPB controller).
By the BpdReadPdo and BpbWritePdo functions, a PDO block including a header
(contains the size of the PDOs and the status register) is provided or expected. In the
case of the writing access, the contents of the status register are ignored.
Abb. 3 Reading/writing the process image
DPRAM
Process output image
Process input image
RWB_Read(...)
{
...
ReadDPRAM()
...
}
RWB_Write(...)
{
...
ReadDPRAM()
...
}
PCI BPB driver