Siemens SPC3 manual Description of the DP Services, SetSlaveAddress SAP55

SPC3 PROFIBUS Interface Center

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) paramet r 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	7	6	5	4	3	2	1	0
Register
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

SPC3 Hardware Description	V1.3	Page 29
Copyright (C) Siemens AG 2003 All rights reserved.		2003/04