Appendix
D
0.2
Double-Precision
Floating-Point
Format
The double precision floating
point
format supported
by
the
TMS34010
C
floating
point
RTS
is
a
64-bit
format: a sign bit.
an
11-bit
biased exponent, a
52-bit
mantissa. The three component fields are positioned in the
64-bit
field
format
as
follows:
6362
5251
o
lsi
EXP
I
MANTISSA
MSB LSB
Figure
0-2.
Double-Precision
Floating
Point
Format
Hence, the sign
bit
is
bit
63
of
the
64-bit
field, the exponent resides in bits
52 through
62, and the mantissa is in bits 0 through
51
.
Given
an
sign
bit
s,
an
exponent
e,
and a mantissa f, then the value V
of
the
floating
point
number
X=(s,e,f)
is
as
follows:
•
If
s = 0, e = 2047, and f = 0, then V =
+infinity
•
If
s = 1, e = 2047, and f = 0, then V =
-infinity
•
If
0 < e < 2047 and f ¢ 0, then V = (_1)5 2e-1023(.f)
(V
=
Not
Valid
if
the number X=(s,e,f) is
not
a normalized floating
point
number.
See
Floating Point Arithmetic, Rounding, and Normalization,
page D-4.)
•
If
s = 0, e = 0, and f = 0, then V = 0
•
For all other cases, V =
Not
Valid
Precision in the double- precision format
is
greater than fifteen decimal digits
and the range
includes the
following:
•
1.11254
x
10-
308
to
8.98847 x
10
308
(positive range)
(1.11254
E-308
to
8.98847 E308, in C format)
• -8.98847 x 1 0
308
to
-1
.11
254
x
10-
308
( negative range)
( -8.98847
E308
to
-1.11254
E-308, in C format)
• 0 (zero)
• + / -
infinity
0-3