Siemens S7 data types - my brain has siezed!

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.

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

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

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.