M80C287 データシートの表示（PDF） - Intel

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M80C287

80-BIT CHMOS III NUMERIC PROCESSOR EXTENSION

Intel 

M80C287

Table 1 M80C287 Data Type Representation in Memory

NOTES

1 S e Sign bit (0 e positive 1 e negative)

2 dn e Decimal digit (two per byte)

3 X e Bits have no significance M80C287 ignores when loading zeroes when storing

4 U e Position of implicit binary point

5 I e Integer bit of significand stored in temporary real implicit in single and double precision

6 Exponent Bias (normalized values)

Single 127 (7FH)

Double 1023 (3FFH)

Extended Real 16383 (3FFFH)

7 Packed BCD (b1)S (D17 D0)

8 Real (b1)S (2E-BIAS) (F0 F1 )

271092 – 2

15

TAG (7)

TAG (6)

TAG (5)

TAG (4)

TAG (3)

TAG (2)

TAG (1)

0

TAG (0)

NOTE

The index i of tag(i) is not top-relative A program typically uses the ‘‘top’’ field of Status Word to determine which tag(i)

field refers to logical top of stack

TAG VALUES

00 e Valid

01 e Zero

10 e QNaN SNaN Infinity Denormal and Unsupported Formats

11 e Empty

Figure 3 M80C287 Tag Word

4

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