Applies To:
  • CitectSCADA 1.00, 1.01, 1.10, 1.11, 2.00, 2.01, 3.10

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. 

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.