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Motorola DSP96002 User Manual

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MOTOROLA

DSP96002 USER’S MANUAL

C-7

specific operation to occur. The result of an invalid operation is a QNaN, as described above.

Examples of invalid operations are 0/0,

∞/∞,

∞−∞

, 0

×∞

, etc.

2.

Division by zero: The result of a division by zero is an infinity (with the correct sign), and the

operation is signaled as an exception.

3.

Overflow: The overflow exception is signaled when the result of an operation exceeds the larg-

est magnitude that the result precision can accommodate. The result generated by the hard-

ware is dependent upon the rounding mode. For round to nearest, an infinity with correct

sign is generated. Round to zero results in the largest possible numerical value the result pre-

cision can accommodate, with correct sign (i. e., the result saturates). Round to -

results in

the largest possible numerical value the result precision can accommodate (i. e., the result sat-

urates) when the overflow is positive. It results in -

when the overflow is negative. Round to

+

results in +

when the overflow is positive, and in the largest negative numerical value the

result precision can accommodate (i. e., the result saturates) when the overflow is negative.

4.

Underflow: Underflow is signaled when both (1) a very small (tiny) number is detected as the

Figure C-5. DP Format in the Data ALU

95 94 93 92

75 74

64

63 62

32 31

11 10

0

S U V

Z

e

Z

Fraction (MSBs)

Fraction (LSBs)

i

Dn.h

Dn.m

Dn.l

S : sign
U : single precision unnormalized tag
V : double precision unnormalized
i : explicit integer

Tiny SP Numbers between +2

Emin

,Exclusive

-1.0

Ч

2

-126

0

+1.0

Ч

2

-126

Figure C-6. Tiny Numbers on the Real Number Line

Figure C-7. SEP Format in the Data ALU

95 94 93 92

75 74

64

63 62

32 31

11 10

0

S U V

Z

e

Z

Fraction

0

i

Dn.h

Dn.m

Dn.l