Siemens S5/S7 Floating-Point Formats

Does anyone have a description of the Siemens S5 and S7 floating-point formats? A web search finds a conversion library at

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which I could buy, but I don't need all the other functions it contains.


Reply to
Chris Doran
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The S7 floating point format is IEEE, big endian format. I don't know what format the S5 uses.

Reply to
Peter Nachtwey

Hi, Wellcome to the number formats... it has been several years when I made this but if I remember well: S7 follows IEEE754 standard S5 is a non-normalized single precision floating point (0,xx)

The formats are: (from bit 31 to bit 0)

S7 : [S 2^7 ... 2^0 2^-1 .... 2^-23] Bits Content


31 Sing of mantisa (1 bit) 30-23 Exponent (8 bits) 22-0 Mantissa of fraction (23 bits)

S5: [SE 2^6 ... 2^0 SM 2^-1 ... 2^-23 Bits Content


31 SE: Sign of exponent (1 bit) 30-24 Exponent (7 bits) 23 SM: Sign of mantissa (1 bit) 22-0 Mantissa (23 bits)

Check also how the numbers are stored in both PLC's. They are in a different way.

I hope this is what you need, Cheers, Quique

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