Profichip VPC3+C User Manual page 37

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+C responds with "no resources"
(RR)!
Address
bit 7-3
bit 2
bit 1
bit 0
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+C have
only 8-bit address registers internally. For a RAM access, VPC3+C 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.
VPC3+C User Manual
Copyright © profichip GmbH 2004-2006
7 6
2AH
0 0
R_Aux_Buf_Sel, Address 2AH:
Don't Care: Read as '0'
Set_Slave_Adr: Set Slave Address
0 = Aux-Buffer 1
1 = Aux-Buffer 2
Chk_Cfg: Check Configuration
0 = Aux-Buffer 1
1 = Aux-Buffer 2
Set_Prm: Set (Extended) Parameter
0 = Aux-Buffer 1
1 = Aux-Buffer 2
Revision 1.03
PROFIBUS DP Interface 6
Bit Position
5 4 3 2
0 0 0
Designation
1 0
R_Aux_Buf_Sel
See below
for coding
37