Siemens SPC3 manual Profibus Interface Center, Reading Inputs

PROFIBUS Interface Center SPC3

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 dat is in the “N” state.

Address

Bit Position

Designation

Control

7

6

5

4

3

2

0

Register

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

01 Dout_Puf_Ptr1

10 Dout_Puf_Ptr2

11 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	7	6	5	4	3	2	1	0
Register
0BH	0	0	0	0	U_	State_	Ind_U_		Next_Dout_Buf_Cmd
					Buffer	U_	Buffer
					Cleared	Buffer
							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’ ot ‘D.’ If no new buffer is present in ‘N,’ there is no change.

The user makes the new data available in ‘U’. Withthe ‘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’ afterall 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.

Page 34	V1.3	SPC3 Hardware Description
2003/04		Copyright (C) Siemens AG 2003. All rights reserved.