Applies To:
  • CitectSCADA 3.xx, 4.xx, 5.00, 5.01, 5.10
Summary:
Izumi counter variables returning unexpected values. 

Solution:
When displaying variables from PLC counter addresses ("CNT"), the data does not display correctly. Citect seems to randomly add 16384 (2^14) to the displayed value (ie. most times it displays correctly, sometimes it adds 16384).

The Izumi counters have a maximum value of  9999, therefore, they only need to use bits 0 to 13 of the counter 16 bit word to store the current counter value.

The 14th bit is being used to temporarily store the state of the counter input (in order to detect the low-to-high transition of the counter input pulse), and this effect may not be noticeable when using a very short on-time pulse to drive the counter. My application was using a 50% duty cycle pulse with a 1Hz frequency to drive the counter.

As a work-around I've been 'AND'ing 16383 to the counter value to mask the upper bits of the word.

This problem has been fixed in the lastest version of the IZUMI driver.

 
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