Applies To:
  • CitectSCADA 1.00 1.01 1.10 1.11 1.20 2.00 2.01

Question: When I used a unit '999' Citect had no trouble compiling the database. When I ran it I started getting LOTS of Memory warning messages. What is the correct value for the unit number field? 

CIT has confirmed this to be a problem in Citect for Windows versions 1.00 to 2.01. This problem has been fixed in version 2.10 and later.

In versions 1.xx to 2.01 the range of the Unit Number was not checked if it was within the valid range. If you entered a Unit Number outside of the valid range you may get memory corruption (Invalid Heap, Already Free error message) or Citect may cause a GPF and you Units may not come online correctly.

In Version 2.10 and later this field is range checked when Citect starts up. If this field is out of range you will get the error message:

Unit <name> Invalid Unit Number
IO Device <name> Invalid IO Device Number

and then Citect will shutdown.

The valid ranges for Unit Number are as follows:

Version 1.xx to 2.01 0 to 254
Version 2.10 0 to 512
Version 3.00 0 to 1024

Note that in version 3.00 the Units form has been renamed to IO Devices.