FASTRAK MANUAL
Rev. G
47
JUNE 2012
‘f’ – Enable Binary Output Format
Syntax:
f
Purpose:
This command enables the binary output data format. Binary format is generally
computer readable while ASCII format is human readable. This format is a 32 bit,
floating point output that is in accordance with the format specified by
ANSI/IEEE Std 754-1985 Specification for Binary Floating Point Arithmetic.
Relatives:
F
Default:
The default output data format is ASCII.
Example:
The user may wish to write a software application for the FASTRAK where a fast
update rate is crucial. In order to reduce data packet size, the FASTRAK could be
set to output in binary instead of ASCII. This can be accomplished with the
command:
f
The FASTRAK will now output binary data.
The notation SingleFP refers to the ANSI/IEEE Standard for Binary Floating-
Point Arithmetic 754-1985 format of data. This is defined in the standard as:
MSB
LSB
Bit 31
Bit 30-23 Bit 22-0
Sign
Exponent Fraction
Byte 3
Byte 2
Byte 1
Byte 0
The IEEE floating-point format uses sign magnitude notation for the mantissa,
and an exponent offset by 127. In a 32-bit word representing a floating-point
number, the first bit is the sign bit. The next 8 bits the exponent, offset by 127 (i.e.
the actual exponent is e - 127). The last 23 bits are the absolute value of the
mantissa with the most significant 1 implied. The decimal point is after the
implied 1, or in other words, the mantissa is actually expressed in 24 bits. In the
normal case an IEEE value is expressed as:
(-1)S * (2**(e-127)) * (01.f) If 0 < e < 255
In special cases:
(-1)S * 0.0
If e = 0 and f = 0
(-1)S * (2**(-126)) * (0.f)
If e = 0 and f <> 0 (denormalized)
(-1)S * infinity
If e = 255 and f = 0 (infinity)
NaN (not a number)
If e = 255 and f <>0
The actual I/O byte sequence is system specific. For the greatest compatibility,
Polhemus has adopted for output the following Intel 80X86 byte ordering: