GE 90-30/20/Micro manual Internal Format of Floating-Point Numbers

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.

Bits 17-32		Bits 1-16
32	17 16	1
		23-bit mantissa
	8-bit exponent
	1-bit sign (Bit

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

Least Significant Register

Bits 1-16

1

Least Significant Bit: Bit 1

Most Significant Bit: Bit 16

Most Significant Register

Bits 17-32

32

17

Least Significant Bit: Bit 17

Most Significant Bit: Bit 32

GFK-0467K Appendix E Using Floating-Point Numbers E-3