S7 STL Dword to Byte

I have been beating myself up for the last couple of hours trying to figure this out. It seems so simple but I really am missing something.

I have a function that I am sending a MD DWord and I need to return just am MB Byte. The value will never be more than +/-500 in the DWord. I have a return bit for negative and a return bit for overflow.

In: DWord value +/- 500
Out: Byte value 0-255, Negative bit, Overflow bit.

Attached is a picture of the latst attempt. I have tried ABS, MOD, AD, (SQR:SQRT), all with the same result.

Assuming I input -38 I would expect 38 in the byte, the negative bit on, the overflow off. I get the negative bit but the byte holds 218.

Please help me to undestand this. Thanks.

I have it, and it was something really simple.
If it is negative just multiply by -1 before the transfer. Jump past it if not.

At that point yes.
I cannot handle a 0 on the recieving end of the communications. A 1 is minute and will not effect results. A zero will be assumed as no communications. But nice catch.

For reference, here is how you can use the abs instruction (which only works on floating point numbers)

Thank you.

I just took the time to look up the DTR and RND instructions in the help files. I am glad it had a description of the IEEE-FP format because I was really wondering how -100 tuns into -1027080192.

Could this be why the SQR then SQRT did not work as expected. I was not using the correct numerical format?

Yes, they only work on floating point numbers as well.