Applies To:
  • CitectSCADA 5.xx, 6.xx
  • CitectHMI 5.xx, 6.xx
Summary:
I am using Version 2.6.8.0 of the S7NT driver to communicate to my Siemens S7 series PLC. I often get an error “request size too big” or “address is out of range” error occurring in my syslog.dat. This has lead to #COM for some tags as well.

What is the cause of this and how do I fix this?

 

Solution:
There have been some changes made to the recent S7NT driver to provide better performance on Ethernet networks for different PLC connections and different S7 series PLC. In particular are changes to the Bit_Block and Max_Length values in the Protdir.dbf. 
This error usually occurs due to incorrect protocol being selected. Selecting the correct Protocol will fix this issue.

 

The S7NT protocol should be changed to reflect the following table:

 

Hardware/Connection Type

Protocol

S7 (generic)

S7NT

S7-200 (any)

SIMPPI

S7-300 (Profibus)

S7NT

S7-300 (MPI)

S7NT

S7-300 (Ethernet)

S7NT300

S7-400 (Profibus)

S7NT

S7-400 (MPI)

S7NT

S7-400 (Ethernet)

S7NT400
 
Keywords:
S7NT, Protdir.dbf, Request Size too big, Address is Out of Range  

Attachments