Profichip VPC3+C - Description of DP Services; Set Slave Address (SAP 55)

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6 PROFIBUS DP Interface

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+C 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+C again. After reading the buffer, the

user generates the SSA_Buffer_Free_Cmd (read operation on address

14H). This makes the VPC3+C ready again to receive another

Set_Slave_Add telegram (for example, from a different DP-Master).

The VPC3+C reacts automatically to errors.

Bit Position

Address

7 6 5 4 3 2 1 0

Designation

14H 0 0 0 0 0 0 0 0

SSA_Buf_

Free_Cmd

SSA_Buf_Free_Cmd, Address 14H:

bit 7-0

Don’t care: Read as ‘0’

Figure 6-3: Coding of SSA_Buffer_Free_Command

38 Revision 1.03

VPC3+C

User Manual