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GFK-0467K Appendix E Using Floating-Point Numbers E-3
E
Internal Format of Floating-Point Numbers
Floating-point numbers are stored in single precision IEEE-standard format. This format requires
32 bits, which translates to two (adjacent) 16-bit PLC registers. The encoding of the bits is
diagrammed below.
16 132 17
Bits 17-32 Bits 1-16
23-bit mantissa
8-bit exponent
1-bit sign (Bit
32)
Register use by a single floating-point number is diagrammed below. In this diagram, if the
floating-point number occupies registers R5 and R6, for example, then R5 is the least significant
register and R6 is the most significant register.
16 1
Bits 1-16
Least Significant Bit: Bit 1
Most Significant Bit: Bit 16
Least Significant
Register
32 17
Bits 17-32
Least Significant Bit: Bit 17
Most Significant Bit: Bit 32
Most Significant Register