Texas Instruments TMS320C3x 사용자 설명서

Floating-Point Formats

5-5

Data Formats and Floating-Point Operation

The exponent field is a 2s-complement number that determines the factor of 2
by which the number is multiplied. Essentially, the exponent field shifts the
binary point in the mantissa. If the exponent is positive, then the binary point is
shifted to the right. If the exponent is negative, then the binary point is shifted
to the left.

For example, if 

man = 01.00000000001

2

 and the 

e = 11

10

, then the binary point

is shifted 11 places to the right, producing the number: 0100000000001

2

,

which is equal to 2049 decimal.

In the short floating-point format, floating-point numbers are represented by a
2s-complement, 4-bit exponent field (e) and a 2s-complement, 12-bit mantissa
field (

man) with an implied most significant nonsign bit (see Figure 5–6).

Figure 5–6. Short Floating-Point Format

Exponent

Sign

Fraction

15

12

11 10

0

Mantissa

Operations are performed with an implied binary point between bits 11 and 10.
When the implied most significant nonsign bit is made explicit, it is located to the
immediate left of the binary point. The floating-point 2s-complement number 

x

in the short floating-point format is given by the following:

x = 01.f 

×

 2

e

if 

s = 0

x = 10.f 

×

 2

e

if 

s = 1

x = 0

if 

e = – 8

You must use the following reserved values to represent 0 in the short floating-
point format:

e = – 8
s =

0

f =

0