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6 PROFIBUS DP Extensions
6.2
Description of the DP Services
6.2.1
Set_Slave_Add (SAP 55)
Sequence for the Set_Slave_Add service
The user can disable this service by setting 'R_SSA_Puf_Ptr = 00H'. The
Station_Address must then be determined, for example, by reading a DIP-
switch or an EEPROM and writing the address in the RAM cell R_TS_Adr.
There must be a non-volatile memory available (for example an external
EEPROM) to support this service. It must be possible to store the
Station_Address and the Real_No_Add_Change ('True' = FFH) parameter
in this EEPROM. After each restart caused by a power failure, the user
must read these values from the EEPROM again and write them to the
R_TS_Adr und R_Real_No_Add_Change RAM registers.
If SAP55 is enabled and the Set_Slave_Add telegram is received correctly,
the VPC3+S enters the pure data in the Aux-Buffer 1/2, exchanges the
Aux-Buffer 1/2 for the Set_Slave_Add-Buffer, stores the entered data
length in R_Len_SSA_Data, generates the New_SSA_Data interrupt and
internally stores the New_Slave_Add as Station_Address and the
No_Add_Chg as Real_No_Add_Chg. The user does not need to transfer
this changed parameter to the VPC3+S again. After reading the buffer, the
user generates the SSA_Buffer_Free_Cmd (read operation on address
14H). This makes the VPC3+S ready again to receive another
Set_Slave_Add telegram (for example, from a different DP-Master).
The VPC3+S reacts automatically to errors.
Address
bit 7-0
Figure 6-3: Coding of SSA_Buffer_Free_Command
44
7
6
14H
0
0
SSA_Buf_Free_Cmd, Address 14H:
Don't care: Read as '0'
Revision 1.04
Bit Position
5
4
3
2
0
0
0
0
Designation
1
0
SSA_Buf_
0
0
Free_Cmd
VPC3+S User Manual
Copyright © profichip GmbH, 2012
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