Delta DVP-ES2 User Manual download pdf (Page 137)

100

101

3. Instruction Set

3-21

Binary Floating Point

DVP-PLC represents floating point value in 32 bits, following the IEEE754 standard:

exponent

mantissa

8-bit 23-bit

b31

Sign bit

0: positive

1: negative

Equation

()

127;.121 =××−

−

Therefore, the range of 32-bit floating point value is from ±2

-126

±2

+128

, i.e. from ±1.1755×10

-38

±3.4028×10

+38

Example 1: Represent “23” in 32-bit floating point value

Step 1: Convert “23” into a binary value: 23.0 = 10111

Step 2: Normalize the binary value: 10111 = 1.0111 × 2

, in which 0111 is mantissa and 4 is

exponent.

Step 3: Obtain the exponent: ∵ E – B = 4  E – 127 = 4 ∴ E = 131 = 10000011

Step 4: Combine the sign bit, exponent and mantissa into a floating point

0 10000011 01110000000000000000000

= 41B80000

Example 2: Represent “-23.0” in 32-bit floating point value

The steps required are the same as those in Example 1 and only differs in modifying the sign bit

into “1”.

1 10000011 01110000000000000000000

=C1B80000

DVP-PLC uses registers of 2 continuous No. to store a 32-bit floating point value. For example,

we use registers (D1, D0) for storing a binary floating point value as below:

S E7 E6 E5 E1 E0 A22 A21 A20 A6 A5 A4 A3 A2 A1 A0

b0b1b2b3b4b5b6b20b21b22b23b24b28b29b30b31

222 22222 2222 222

7 6 5 1 0 -1 -2 -3 -17 -18 -19 -20 -21 -22 -23

D1(b15~b0) D0(b15~b0)

8 bits of exponent

23 bits of mantissa

Sign bit (0: positive 1: negative)

When b0~b31 is 0, the content is 0.

Hidden decimal point

Decimal Floating Point

 Since the binary floating point value is not very user-friendly, we can convert it into a decimal

floating point value for use. However, please note that the floating point operation in DVP-PLC is

still operated in binary floating point format.

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Delta DVP-ES2 User Manual Page 137

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