Any way to use double data types in RsLogix?

opmal7 · Jul 18, 2016

I'm using RsLogix Micro Starter Lite for some basic PLC programming. I have an incoming RS-422 message that is composed of hex bytes. Some of the data in that message are integers, SP float, and DP float. I've been able to extract the info for the integers and SP floats into other data types using COP and MOV commands, but I don't have an option for a DP Float data type.

Anyone know if doubles are available in other RSlogix versions, or if there is a work around?

harryting · Jul 18, 2016

No. No version of RSLogix supports double-precision floats.

opmal7 · Jul 18, 2016

harryting said:
No. No version of RSLogix supports double-precision floats.

Rats...I've got some thinking to do then. Thanks for the info

bernie_carlton · Jul 18, 2016

I've never tried this but some bit moving may give a useable value, assuming the double precision value is within the range of the single precision.

Transfer the following bits (starting with the most significant and working downward) from the double precision location to the single precision location.

Preserve the upper 9 bits of the double precision into the upper bits of the single precision.

Skip the next 3 bits of the double precision

Preserve the next 23 bits. Ignore the remaining bits of the double precision number.

DwSoFt · Jul 18, 2016

bernie_carlton said:
I've never tried this but some bit moving may give a useable value, assuming the double precision value is within the range of the single precision.

Transfer the following bits (starting with the most significant and working downward) from the double precision location to the single precision location.

Preserve the upper 9 bits of the double precision into the upper bits of the single precision.

Skip the next 3 bits of the double precision

Preserve the next 23 bits. Ignore the remaining bits of the double precision number.

If this works, well then good job! where did you get is littletidbit of information from?

bernie_carlton · Jul 18, 2016

I just looked up the structure (yeah Wikipedia) of both types of floating point and determined what I could toss away realizing that the precision those bits represent is obviously what we would be giving up.

I would like to find out if this would work - looking at the structures it seems reasonable.

Edit - actually thinking about it some more it may not be this simple regarding the bits in the exponent.

MichaelG · Jul 20, 2016

there are AOI's that have been written for double precision control logix
sorry I just cannot remember where they are located

nhatsen · Jul 22, 2016

MichaelG said:
there are AOI's that have been written for double precision control logix
sorry I just cannot remember where they are located

http://search.rockwellautomation.co...fields=*&lang=en&hl=en&dnavs=double_precision

MichaelG · Jul 22, 2016

nhatsen said:
http://search.rockwellautomation.co...fields=*&lang=en&hl=en&dnavs=double_precision

thank you
:site:

Any way to use double data types in RsLogix?

opmal7

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