Siemens SPC3 manual Structure of the Diagnostics Buffer, WriteReadData / DataExchange DefaultSAP

Figure 6.9: Coding Diag_Puffer_SM, New_Diag_Cmd

6.2.4.2 Structure of the Diagnostics Buffer:

The user transfers the diagnostics buffer displayed in the figure below to SPC3. The first 6 bytes are space holders, except for the three least significant bit positions in the first byte. The user stores the diagnostics bits, ‘Diag.Ext_Diag’ ‘Diag.Stat_Diag,” and Diag.Ext.Diag_Overflow’ in these three bit positions. The remaining bits can be assigned in any order. When sending, SPC3 pre-processes the first six bytes corresponding to the standard.

The ‘Ext-Diag_Data’ the user must enter into the buffers follow after the SPC3-internal diagnostics data. The three different formats are possible here (device-related, ID-related, and port-related). In addition to the ‘Ext_Diag_Data,’ the buffer length also includes the SPC3 diagnostics bytes (R_Len_Diag_Puf1, R_Len_Diag_Puf2).

6.2.5 Write_Read_Data / Data_Exchange (Default_SAP)

6.2.5.1 Writing Outputs

SPC3 reads the received output data in the D buffer. After error-free receipt, SPC3 shifts the newly filled

buffer from ‘D’ to ‘N.’ In addition, the ‘DX_Outnterrupt’I is generated. The user now fetches the current output data from ‘N.’ The buffer changes from ‘N’to ‘U’ with the ‘Next_Dout_Buffer_Cmd,’ so that the current data of the application can be sent back for the master’s Read_Outputs.

If the user’s evaluation cycle time is shorter than the bus cycle time, the user does not find any new buffers with the next ‘Next_Dout_Buffer_Cmd’ in ‘N.’ Therefore, the buffer exchange is omitted, At a 12 Mbd baud rate, it is more likely, however, that the user’s evaluation cycle time is larger than the bus cycle time. This makes new output data available in ‘N’ several times before the user fetches the next buffer. It is guaranteed, however, that the user receives the data last received.

For ‘Power_On’, ‘Leave_Master’ and the Global_Control-Telegram ‘Clear,’ SPC3 deletes the D buffer and then shifts it to ‘N.’ This also takes place during the power up (entering into ‘Wait_Prm’). If theuser fetches this buffer, he receives the ‘U_buffer cleared’ display during the ‘Next_Dout_Buffer_Cmd.’ If the user is still supposed to enlarge the output data buffer after the Check_Config telegram, the user must delete this delta in the N buffer himself (possible only during the power-up phase in the ‘Wait_Cfg’ state).

If ‘Diag.Sync_Mode = 1’, the D buffer is filled butnot exchanged with the Write_Read_Data-Telegram, but rather exchanged at the next Sync or Unsync.