Applies To:
  • CitectSCADA 1.10 1.11 1.20 2.00 2.01
Summary:
Several users have been having problems with the performance of the HITACHI driver. If you configure your database as follows you will be able to get the best possible performance from the HITACHI driver.

Solution:
The HITACHI protocol can only read a small number of variables when you use the X, Y and R data types. This is a limitation of the HITACHI PLC. The L and M data types can be read in much larger numbers and will give better performance. The Citect HITACHI protocol restricted the maximum number of variables in the L and M data types to the same as X, Y and R types, this resulted in lower performance.

The HITACHI Driver has been modified in version 2.10 to allow Citect to read the L and M types in blocks of 1920 contiguous bits. It is recommended that the X, Y and R types are NOT used as they are still restricted to blocks of 240 bits.

For the best performance use only the WM and M types, To get data from any other types (such as R, X, Y, WX, WY) copy their values to the WM and M types. Block the data together as described in Citect Design Guide under 'Performance Considerations'.

These recommendations are very important. Failure to follow these recommendations will greatly slow down communication speed.
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