Applies To:
  • CitectSCADA 5.xx
Summary:
I have configured my Citect project to use multiple I/O Devices per channel and use Cicode function IODeviceControl() to disable/enable some of the I/O Devices. After a period of time, Citect would report errors "Too many units per channel" and some of the devices would never go online again.

What could be causing the errors "Too many units per channel"?

 

Solution:
The errors "Too many units per channel" will only occur under a very specific operating condition. The exact sequence which these errors occur are described below.

Consider the scenario: Using multiple I/O Devices per channel and some of the I/O Devices have been disabled (on the IOServer side) using Cicode function IODeviceControl(). If after some of the I/O Devices have been disabled and then some of the remaining I/O Devices go offline (eg. due to timeout or cable been disconnected). At the next driver WatchTime, Citect will attempt to bring some of the offline iodeivces back online for communication.

If you now then re-enable some of the I/O Devices (which have been disabled previously) then Citect will display the error "Too many units per channel".

Citect has confirmed this to be a problem in the CCM driver up to and including version V2.01.000. This problem has been fixed in version V2.01.01.001 and above.

 
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