Siemens 6GK7242-7KX30-0XE0 Manual Do Utilizador

Notes on operation and configuration 

 

4.7 Data transfer between communications partners 

 

CP 1242-7 

44

 

Operating Instructions, 03/2012, C79000-G8976-C247-03 

4.7.3 

Master station reads data from the S7-1200 (read) 

Requirements 

●  The OPC server has been started on the telecontrol server (an OPC client has connected 

to the telecontrol server). 

●  The TC_SEND instruction was called at least once in the CPU of the station. 

This creates the send process image on the CP. 

 

 

Note 
Item name of the OPC client   
The process image on the CP is created as a data block. The read access of an OPC 

client to the process image must be transferred by the DB1 item to the CP. 

Sequence 

1.  With the DB1, DBx,y item, the OPC server sends a read job for "x" bytes starting at offset 

"y" to the CP. 

2.  The CP checks whether "x" bytes starting at offset "y" exist in the process image. 
3.  Reaction of the CP: 

–  If "x" bytes starting at offset "y" exist in the image, the data ("x" bytes) is sent to the 

telecontrol server. 

–  If the image is smaller than x + y bytes, the read job is acknowledged negatively. 

The OPC client receives an error message from the OPC server of the telecontrol 

server. 

4.7.4 

Master station sends data to the S7-1200 (write, TC_RECV) 

Sequence 

1.  The telecontrol server writes "x" bytes starting at offset "y" in a write job to the CP. 
2.  The CP saves the data at position "y" in the receive process image. 

–  If the receive process image does not yet exist on the CP or is smaller than x + y 

bytes, the data is saved as a new image. Data areas without value are filled with the 

value 0. 

–  If the data area of the write job is smaller than the image, the image is not reduced in 

size. 

3.  The CP always transfers the entire image to TC_RECV. 

Note: Remember this when specifying the size of the "LEN" parameter of TC_RECV.