IDEC MICROSmart FC6A Series Ladder Programming Manual page 253

Floating Point Value Notation on LCD
Whether or not F (float) LCD notation uses decimal notation or exponent notation is determined according to the single-
precision floating point definition in IEEE 754 and the internal system function included in the CPU module.
The IEEE 754 single precision format consists of three fields: a 23-bit fraction, f; an 8-bit biased exponent, e; and 1-bit sign,
s. These fields are stored contiguously in one 32-bit word, as shown in the figure below. Bits 0:22 contain the 23-bit fraction,
f, with bit 0 being the least significant bit of the fraction and bit 22 being the most significant; bits 23:30 contain the 8-bit
biased exponent, e, with bit 23 being the least significant bit of the biased exponent and bit 30 being the most significant;
and the highest-order bit 31 contains the sign bit, s.
Bit Bit
31 30
s e[30:23]
8-bit biased exponent
Sign bit (0: positive, 1: negative)
The table below shows the correspondence between the values of the three constituent fields s, e, and f and the value
represented by the single precision format bit pattern.
When the value is ±0, denormalized number, or normalized number, the value is displayed according to the internal system
function of the CPU module.
Value
±0
Denormal numbers
Normal numbers
±∞ (± infinities)
NaNs (Not a number)
Example: This table shows the representation on the LCD for the following floating-point values.
1234567
12345678
1234567.8
0.0001
0.00001
0.000001
0.0000001
0.123456
0.1234567
0.12345678
0.0000012
1.2345678
0
0.0001234568
Bit Bit
23 22
Exponent Field e
e=0
e=0
0<e<255
e=255
Value
FC6A S MICROS L
ERIES MART
f[22:0]
23-bit fraction
Fraction Field f
f=0
f≈0
Arbitrary
f=0
f≈0
1234567
1.234568E+07
1234568
0.0001
1E-05
1E-06
1E-07
0.123456
0.1234567
0.1234568
1.2E-06
1.234568
0
0.0001234568
P M
ADDER ROGRAMMING ANUAL
12: D
ISPLAY
Representation
0
• Displayed in decimal notation
0.0001 ≤ | Value | < 9,999,999.5
(Number of significant digits is 7 digits, 8th
digit is rounded)
• Displayed in exponent notation
| Value | < 0.0001
| Value | ≥ 9,999,999.5
INF
NAN
Representation in LCD
FC9Y-B1726
I
NSTRUCTIONS
Bit
0
12-5