Siemens S7 data types - my brain has siezed!

[Ned_Flanders]

I am trying to compare two values, one comes from modbus via a datablock in the range of 0 - 65535. "Int" in the datablock.
This is displayed on a Pro face gp3500 HMI correctly and in the program.

I am trying to compare this with a level set on the HMI and the HMI has 16 bit dec 0 - 65535, 0 - 200 as its range.

If I exceed 32768, by typing 100 on the HMI (Half "Full scale") the value displayed in the program becomes a minus value!

What am I doing wrong? I thought 16 bits would display 65535.

 

[Pandiani]

markie,

16 bits can represent 0 to 65535 or from -32768 to + 32767. There are always signed/unsigned types you need to think of. Probably, this is why you get negative value when you try to enter 32768 (which is above max positive value).

Regards,
Pandiani

 

[Thim]

Is this comparing the same like you a few posts before??
Then maybe you would need to compair for >I instead of >D

 

[Ned_Flanders]

What a plank! Should have RTFM - on a INT the msb is the sign +/-, so if the msb goes to 1, the display shows a negative value.

Still had some maths to do , and reset my HMI inputs to 0-32767! D'oh.