How Do I Read a REAL as a SINT

[Green Man]

Folks

I have a bit of a dilema here. On a profibus network, Prosoft on ControlLogix Platform, I have an instrument that is giving me two values as REAL, however the Prosoft Card reads these as SINT!!!

Just not sure how to handle this data and retrieve it from the instrument, transmitted as REAL, and read it as a SINT.

Any pointers would be greatly appreciated.

Green Man

 

[OkiePC]

Does the Prosoft card read each Real (32 bit float) as two 16 bit integers? If so, you may be able to perserve this bit pattern by copying those INTs into a Real using the COP instruction.

When using the COP instruction, the destination data type determines the bit-length of the data which gets copied, so if the destination is a Real (or DINT), a Length of 1 in the instruction will result in 32 consecutive bits being copied. If the source is a single integer, the bits will be copied from two consecutive integers.

 

[Green Man]

Thanks that makes sense when explained. Had a hunch kt mkght be this instruction.

 

[chavak]

Hi,

I recently came across the same situation. Apart from the data part you need to know how is the byte order your device giving out the data [low and high].

As the Profibus addressing is SINT, I had to use 4 separate Bit Field Distribute to combine the read data from 4 SINT tags to a DINT. Then convert them to real. In my case, I was able to scale the value at the device, then after combining the value to a DINT tag, divide it to convert back to real.

For eg, the device giving out 1.23456, I convert it to 123456 at device and in PLC, after reading it to a DINT, divide the DINT by 100000 to get back 1.23456.

Note: Study the byte order of the read data.

Regards
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