Profichip VPC3+S - Page 43

PROFIBUS DP Extensions 6
VPC3+S User Manual
Revision 1.04
43
Copyright © profichip GmbH, 2012
above. The Aux-Buffer 1 must always be available, Aux-Buffer 2 is optional.
If the data profiles of these DP telegrams are very different (for example the
length of the Set_Prm telegram is significantly larger than the length of the
other telegrams) it is suggested to make an Aux-Buffer 2 available
(R_Aux_Buf_Sel: Set_Prm = 1) for this telegram. The other telegrams are
then read via Aux-Buffer 1 (R_Aux_Buf_Sel: Set_Slave_Adr = 0, Chk_Cfg
= 0). If the buffers are too small, the VPC3+S responds with “no resources”
(RR)!
Address
Bit Position
Designation
7
6
5
4
3
2
1
0
2AH
0
0
0
0
0
Set_ Slave_Add
Chk_Cfg
Set_Prm
R_Aux_Buf_Sel
See below
for coding
R_Aux_Buf_Sel, Address 2AH:
bit 7-3
Don’t Care: Read as ‘0’
bit 2
Set_Slave_Adr: Set Slave Address
0 = Aux-Buffer 1
1 = Aux-Buffer 2
bit 1
Chk_Cfg: Check Configuration
0 = Aux-Buffer 1
1 = Aux-Buffer 2
bit 0
Set_Prm: Set (Extended) Parameter
0 = Aux-Buffer 1
1 = Aux-Buffer 2
Figure 6-2: Aux-Buffer Management
The user makes the configuration data (Get_Cfg) available in the
Read_Config-Buffer for reading. The Read_Config-Buffer must have the
same length as the Config-Buffer.
The RD_Input telegram is serviced from the Din-buffer in the ‘D’ state and
the RD_Output telegram is serviced from the Dout-Buffer in the ‘U’ state.
All buffer pointers are 8-bit segment addresses, because the VPC3+S have
only 8-bit address registers internally. For a RAM access, VPC3+S adds an
8-bit offset address to the segment address shifted by 4 bits (result: 12-bit
physical address) in case of 4K Byte RAM or shifted by 3 bits (result: 11- bit
physical address) in case of 2K Byte RAM. With regard to the buffer start
addresses, this specification results either in a 16-byte or in an 8-byte
granularity.