Profibus interface center, Spc3 – Siemens SPC3 User Manual
Page 36
PROFIBUS Interface Center
SPC3
Page 34
V1.3
SPC3 Hardware Description
2003/04
Copyright (C) Siemens AG 2003. All rights reserved.
The user can read the buffer management state with the following codes for the four states: ‘Nil’,
‘Dout_Puf_Ptr1-3’. The pointer for the current data is in the “N” state.
Address
Bit Position
Designation
Control
Register
7
6
5
4
3
2
0
0AH
F
U
N
D
Dout_Puffer_SM
X1
X2
X1
X2
X1
X2
X1
X2 See below for coding.
X1
X2 Coding
0
0
Nil
0
1
Dout_Puf_Ptr1
1
0
Dout_Puf_Ptr2
1
1
Dout_Puf_Ptr3
Figure 6.11: Dout_Buffer Management
When reading the ‘Next_Dout_Buffer_Cmd’ the user gets the information which buffer (U-buffer) belongs to
the user after the change, or whether a change has taken place at all.
Address
Bit Position
Designation
Control
Register
7
6
5
4
3
2
1
0
0BH
0
0
0
0
U_
Buffer
Cleared
State_
U_
Buffer
Ind_U_
Buffer
Next_Dout_Buf_Cmd
0
1
Dout_Buf_Ptr1
1
0
Dout_Buf_Ptr2
1
1
Dout_Buf_Ptr3
0
No new U buffer
1
New U buffer
0
U buffer contains data
1
U buffer was deleted
Figure 6.12: Next_Dout_Puffer_Cmd
The user must delete the U buffer during initialization so that defined (deleted) data can be sent for a
Read_Output Telegram before the first data cycle.
6.2.5.2 Reading Inputs
SPC3 sends the input data from the D buffer. Prior to sending, SPC3 fetches the Din buffer from ‘N’ to ‘D.’
If no new buffer is present in ‘N,’ there is no change.
The user makes the new data available in ‘U’. With the ‘New_Din_buffer_Cmd,’ the buffer changes from ‘U’
to ‘N’. If the user’s preparation cycle time is shorter than the bus cycle time, not all new input data are sent,
but just the most current. At a 12 Mbd baud rate, it is more probable, however, that the user’s preparation
cycle time is larger than the bus cycle time. Then SPC3 sends the same data several times in succession.
During start-up, SPC3 first goes to ‘DATA_EX’ after all parameter telegrams and configuration telegrams
are acknowledged, and the user then makes the first valid Din buffer available in ‘N’ with the
‘New_Din_Buffer_Cmd.
If ‘Diag.Freeze_Mode = 1’, there is no buffer change prior to sending.
The user can read the status of the state machine cell with the following codings for the four states: ‘Nil’,
‘Dout_Puf_Ptr1-3.’ (See Figure 3.13.) The pointer for the current data is in the “N” state.