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Topic starter
I have a customer that wants to read and display a 64 bit signed integer in PcVue. Ignoring the issue of how the number gets into PcVue in the first place, what are the issues with managing (saving and displaying) such large numbers in PcVue. I am sure there must be some!
Cheers, Robin
Posted : 01/10/2015 2:27 pm
At least you must keep the option "Use register variables as double in Scada Basic" in the general Settings/Program. It's true by default.
Nico
Posted : 01/10/2015 3:25 pm
If we trust Wikipedia it can be Signed: From −9,223,372,036,854,775,808 to 9,223,372,036,854,775,807, from −(2exp(63)) to 2exp(63) − 1
and Unsigned: From 0 to 18,446,744,073,709,551,615 which equals 2exp(64) − 1
In PcVue if I try to put this value in a register it says value out of limits
Posted : 01/10/2015 3:33 pm
Indeed!
According our super training manual register variable has the folling limits:
Register: -3.37E+38 to +3.37E+38
Nico
Posted : 01/10/2015 4:19 pm
Topic starter
The customer has told be that the 64 bit value is supplied as 4 x 16 bit words (modbus)
I had a play using 4 words (as registers) , shifted left by 0, 16, 32 & 48 bits and then added together - all using expressions. It almost works but there are two problems.
- Larger numbers loose accuracy. I think this is because PcVue stores register variables as 32 bit floats (yes anyone?)
- Very large numbers are displayed as negative values. I suppose something is interpretting the top bit as a sign bit?
Anymore comments anyone?
Cheers, Robin
Posted : 01/10/2015 6:05 pm