Applies To:
  • CitectSCADA
Summary:
In the condition that POLLTIME is non zero and IOdeviceControl() has been used to "disable" the driver the MODBUS driver will still reading the com buffer. This action removes data intended for the Cicode ComRead() function.

Drivers affected:

  • MODBUS
  • MODBUSA
  • MOORE
  • MODCELL.  

Solution:
This problem has been fixed in version 2.04 of the affected drivers. However, it must be stressed that (where possible) the driver should be used in interrupt mode, ie POLLTIME=0.

If the driver works in poll mode but not in interrupt mode try using the DELAY parameter. In the CITECT.ini file use the following:

[MODBUS]
POLLTIME=0
DELAY=XX

Where XX is the value that previously worked as the polltime parameter. Some experimentation may be necessary to get best performance. 
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