Siemens S5 Floating Point Format

Does anyone know where I can find a complete description of the S5 floating point format. I am not a PLC programmer but must interface to a number of S5 PLCs and must convert their internal S5 Floating format to IEEE single precision floating point. I especially need information regarding negative exponent and negative mantissa handling.

Here is the format from a siemens manual v=sign bit:

Most PLCs, including Simatic S5 (135U and up) and S7, use the IEEE FP 32-Bit binary memory format to work with REAL numbers:

(-1^s)*(1.f)*(2^e-127) for e=1..254 (normalised numbers) or (-1^s)*(0.f)*(2^-126) for e=0 (denormalised numbers).

Simon, I don't know in what Siemens manual you've found that picture, but that's not what I've found in the on-line help in STEP 7 V5.3. I've attached that info in a PDF file.

Kind regards,

... from the 'Simatic S5 Software Reference Guide'

hi,
have you got a copy, and how can i get one??

Here's a link to a manual that you can download and print the relevant sections: http://support.automation.siemens.com/WW/skm/frameset.asp?url=%2FWW%2Fllisapi%2Edll%2F1085940%3Ffunc%3Dll%26objId%3D1085940%26objaction%3Dcsopen%26siteid%3Dcseus%26skm%3D1%26lang%3Den%26query%3D928b%2Bprogramming%26ehbid%3Dhtml%255F76%252Fehb%252F1085940%252Ehtm%26nodeid%3D1118050&Query=928b+programming&SearchArea=alle&id=1085940&F11Marker=true&siteid=cseus&query2=&modelled=&lang=en