Lenze 3241C - Manual (Page 17)

API functions 3

15
3.4.4 SDO block structure
SDO memory area header 1. DWORD
Status register 2. DWORD
BpbSdoBlockHeader
SDOs
3. DWORD
…
n. DWORD
(binary data, according to SDO
package formats)
The structure of the SDO memory area results from the different SDO package
formats. The following package formats are defined there:
Write request (BpbSdoHeader, BpbWrite)  status message (BpbSdoHeader)
Read request (BpbSdoHeader)  response (BpbSdoHeader, BpbRead)
Each SDO (FIFO telegram) starts with a header, which is identical for the IPC and the
BPB controller:
Header
Structural element Type Bits Description FIFO
Index WORD 16-31 Index of the parameter
Subindex BYTE 8-15 Subindex of the parameter
Control BYTE 0-7 Bit 7 = 0 (read) / 1 (write)
Bit 0-6 = job number
1 DWORD
Via the index and subindex, the BPB controller basically decodes the action to be
executed and, if required, generates a suitable command for the BPB master, which
the backplane bus master in turn transmits to the I/O module/s. Since a telegram on
the BPB must only contain a maximum of 64 bytes of user data, a data volume greater
than that, if necessary, has to be fragmented into several individual telegrams by the
IPC. After processing, the BPB controller sends a status message on the response FIFO
to the IPC. The response contains the job number and one byte regarding the success
of the action.