Spc3 profibus interface center – Siemens SPC3 User Manual
Page 31
SPC3
PROFIBUS Interface Center
SPC3 Hardware Description
V1.3
Page 29
Copyright (C) Siemens AG 2003 All rights reserved.
2003/04
6.2 Description of the DP Services
6.2.1 Set_Slave_Address (SAP55)
6.2.1.1 Sequence for the Set_Slave_Address Utility
The user can disable this utility by setting the ‘R_SSA_Puf_Ptr = 00H’ buffer pointer. The slave address
must then be determined, for example, by reading a switch, and written in the R_TS_Adr. RAM register.
The user must make a retentive memory possibility available (for example, EEPROM) to support this utility.
It must be possible to store the ‘station address’ and the ‘Real_No_Add_Change’ (‘True’ = FFH) parameter
in this external EEPROM. After each restart caused by a power failure, the user must again make these
values available to SPC3 in the R_TS_Adr und R_Real_No_Add_Change RAM register.
If SAP55 is enabled and the Set_Slave_Address telegram is correctly accepted, SPC3 enters all net data in
the Aux-Puffer1/2, exchanges the Aux buffer1/2 for the SSA buffer, stores the entered data length in
‘R_Len_SSA_Data’, generates the ‘New_SSA_Data’ interrupt and internally stores the new ‘station address’
and the new ‘Real_No_Add_Change’ parameter. The user does not need to transfer this changed
parameter to SPC3 again. After the user has read the buffer, the user generates the
‘SSA_Puffer_Free_Cmd’ (read operation on address 14H). This makes SPC3 again ready to receive an
additional Set Slave Address telegram (such as from another master).
SPC3 reacts independently when there are errors.
Address
Bit Position
Designation
Control
Register
7
6
5
4
3
2
1
0
14H
0
0
0
0
0
0
0
0
SSA_Puffer_Free_Cmd
don´t care
Figure 6.3: Coding SSA_Buffer_Free_Cmd
6.2.1.2 Structure of the Set_Slave_Address Telegram
The net data are stored as follows in the SSA buffer:
Byte
Bit Position
Designation
7
6
5
4
3
2
1
0
0
New_Slave_Address
1
Ident_Number_High
2
Ident_Number_Low
3
No_Add_Chg
4-243
Rem_Slave_Data additional application-
specific data
Figure 6.4: Data Format for the Set_Slave_Address Telegram