Applies To:
  • CitectSCADA 1.00, 1.01, 1.10, 1.11, 2.00, 2.01, 3.10
Summary:
The CCM protocol does not support M variables when communicating with a GE90/30 PLC. With remapping, you could get the effect of reading M variables. By remapping you could configure your project assuming reading M variables, while the runtime would read the remapped registers. To allow users to remap M variables, the M variable type must be recognised by the Citect Compiler. Because of this, compiler only support for M variables was allowed in Version 1.XX of Citect for Windows.

However, this compiler support was causing confusion to some users. These users assumed that as Citect would compile the M type variables, the protocol must allow reading of these variables directly from the PLC. As the CCM protocol does not support M variables Citect cannot read these variables. So it has been decided not to support the remapping of variables in version 1.20, 2.00 and later. 

Solution:
The SNP protocol is now available which supports the M variables correctly. If you need support for M variables you should upgrade your Citect system to version 3.10 and use the SNP protocol.

If using CCM protocol and for new users don't use M type variables. If you have already used remapping of M type variables from version 1.XX, when you upgrade to newer version of Citect, your project will no longer compile. To maintain M variable support, save the file \CITECT\BIN\GE_9030.DBF from your existing version, and copy it back to the BIN directory after you have installed the new version.

If you don't have a copy of the GE_9030.DBF file, you can add the following record to this file. You will need a database editing tool to add this record, eg dBase, Excel etc:

   M%U ¦ 10     ¦ 0       ¦ 1      ¦ 1       ¦ 2048 

Note: CIT will not put the M variable support back in as it causes too many problems for some users. If you want to keep M variable support you must maintain your database on each upgrade. 
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