From integer to integer: casting and conversion details?

[biscay]

Dear colleagues:

I would like to know some details about the way LabVIEW (in particular, its FPGA module) performs some data type conversions.

For example, if you have a negative-valued INT32 variable, and make its wire pass through that "To Unsigned Long Integer" bullet-like box, what's the result? What happens to the MSb?

Thank you and regards.

Biscay.

[altenbach]

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biscay wrote:

What happens to the MSb?

Why don't you just try it? Would seem much faster than asking here. 😄

[biscay]

Good point. The thing is that I expect these things to be explained in the otherwise very complete Labview's Help menu.

[RavensFan]

I bet if you looked at the very complete Microsoft Visual Studio help system for the same question, you don't find it explained there either.

[crossrulz · Accepted solution]

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@biscay wrote:

For example, if you have a negative-valued INT32 variable, and make its wire pass through that "To Unsigned Long Integer" bullet-like box, what's the result? What happens to the MSb?

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In this case, nothing happens the the MSb.  The data is literally just reinterpreted (the binary values are exactly the same).

[biscay]

Thank you, Crossrulz, for your quick answer.

Other related question is, does anyone know how time- and resource-consuming is the conversion from SGL to whatever FXP, on an FPGA target?

There are plenty of examples suggesting to turn your ADC-acquired FXP values to SGL, which I see as very handy (given that, for example, the official PDI vi no longer makes use of I16s: it now uses SGL values). In fact, for me, it is reasonable to think that that FXP->SGL conversion is pretty straightforward. However, if you need to get back to the FXP world, I see that things are blurrier. And, again, LabVIEW's help is of little help here!

Biscay.