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Decoding floating point numbers, Waveform template – Teledyne LeCroy X-STREAM OSCILLOSCOPES Remote Control User Manual

Page 297

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Waveform Template

WM-RCM-E Rev D

ISSUED: February 2005

291

DECODING FLOATING POINT NUMBERS

Single precision values are held in four bytes. If these are arranged in decreasing order of value we get the
following bits:


bit 31, bit 30, bit 29, bit 28 . . . . . bit 3, bit 2, bit 1, bit 0


We must remember that if the byte order command CORD has been set for low byte first, the bytes as

received in a waveform descriptor will be received in the reverse order. But within a byte, the bits keep their
order, highest at the left as expected.


From these bits we are to construct three numbers that are to be multiplied together: S x E x F. These in turn

are constructed as follows:

S = (-1)

s

E = 2

(e - 127)

F = 1 + f

and it is s, e, and f that are calculated directly from the 32 bits. The diagram below illustrates the calculation of

the vertical gain example of Chapter 4.