Profibus interface center, Spc3, 6 profibus-dp interface – Siemens SPC3 User Manual

Page 28

PROFIBUS Interface Center

SPC3

Page 26

V1.3

SPC3 Hardware Description

2003/04

6 PROFIBUS-DP Interface

6.1 DP_Buffer Structure

The DP mode is enabled in the SPC3 with ‘DP_Mode = 1’ (see mode Register0). In this process, the
following SAPS are fixed reserved for the DP mode:

Default SAP:

Data exchange (Write_Read_Data)

SAP53:

reserved

SAP55:

Changing the station address (Set_Slave_Address)

SAP56:

Reading the inputs (Read_Inputs)

SAP57:

Reading the outputs (Read_Outputs)

SAP58:

Control commands to the DP-Slave (Global_Control)

SAP59:

Reading configuration data (Get_Config)

SAP60:

Reading diagnostics information (Slave_Diagnosis)

SAP61:

Sending parameter setting data (Set_Param)

SAP62:

Checking configuration data (Check_Config)

The DP Slave protocol is completely integrated in the SPC3 and is handled independently. The user must
correspondingly parameterize the ASIC and process and acknowledge transferred messages. Except for
the default SAP, SAP56, SAP57, and SAP58, all SAPS are always enabled. The remaining SAPS are not
enabled until the the DP Slave Machine (DP_SM) goes into the ‘DATA_EX’ state. The user has the
possibility of disabling SAP55. The relevant buffer pointer R_SSA_Puf_Ptr must be set to ‘00H’ for this
purpose. The DDB utility is disabled by the already described initialization of the RAM cells.

The DP_SAP buffer structure is displayed in Figure 6.1. The user configures all buffers (length and buffer
beginning) in the ‘offline state.’ During operation, the buffer configuration must not be changed, except for
the length of the Dout-/Din buffers.

The user may still adapt these buffers in the ‘Wait_Cfg’ state after the configuration telegram
(Check_Config). Only the same configuration may be accepted in the ‘DATA_EX’ state.

The buffer structure is divided into the data buffer, diagnostics buffer, and the control buffer.

Both the output data and the input data have three buffers each available with the same length. These
buffers function as change buffers. One buffer is assigned to the ‘D’ data transfer, and one buffer is
assigned to the ‘U’ user. The third buffer is either in a Next ‘N’ state or Free ‘F’ state, whereby one of the
two states is always unoccupied.

Two diagnostics buffers that can have varying lengths are available for diagnostics. One diagnostics buffer
is always the ‘D’ assigned to SPC3 for sending. The other diagnostics buffer belongs to the user for
preparing new diagnostics data, ‘U.’

The SPC3 first reads the different parameter setting telegrams (Set_Slave_Address, and Set_Param) and
the configuring telegram (Check_Config) into Aux-Puffer1 or Aux-Puffer 2.....