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OVERVIEW OF NUMERIC PROCESSING
Table 1-2. Numeric Data Types
Data Type Bits
Significant
Approximate Range (Decimal)
Digits (Decimal)
Word integer 16 4
-32,768
::s
X
::s
+32,767
Short integer
32 9
-2X10
9
::S
X::s
+2X10
9
Long integer
64
18
-9X10
'8
::S
X::s
+9X10
'8
Packed decimal
80
18
-99
... 99::S X::s
+99
...
99
(18
digits)
Short
real'
32
6-7
8.43X 1
0.
37
::s1
X I::s
3.37X10
38
Long real'
64
15-16
4.19X
10.
307
::S
I X I
::S
1.67X
1 0
308
Temporary real
80
19
3.4 X 1
0.
4932
::S
I X I
::S
1.2 X 1 0
4932
Table 1-3. Principal
NPX
Instructions
Class
Instruction Types
Data Transfer Load (all data types), Store (all data types), Exchange
Arithmetic
Add, Subtract,
Multiply, Divide,
Subtract
Reversed, Divide
Reversed, Square Root,
Scale, Remainder, Integer Part, Change
Sign,
Absolute Value, Extract
Comparison Compare, Examine, Test
Transcendental
Tangent, Arctangent, 2
x
-1,
Y·Log
2
(X
+
1),
Y·Log
2
(X)
Constants
0,
1,
71",
Log
,0
2,
Log.2, Log
2
10, Log
2
e
Processor Control
Load Control Word, Store Control Word, Store Status Word,
Load Environment, Store Environment, Save, Restore,
Clear
Exceptions, Initialize, Set Protected Mode
In addition, all of the development tools supporting the 8086 and 8087 can also be used to develop
software for the 80286 and 80287 operating
in
Real-Address mode.
All of these high-level languages provide programmers with access to the computational power and
speed of the 80287 without requiring an understanding of the architecture of the 80286 and 80287
chips. Such architectural considerations
as
concurrency and data synchronization are handled automat-
ically by these high-level languages. For the ASM286 programmer, specific rules for handling these
issues are discussed in a later section of this supplement.
Hardware Interface
As
an extension of the 80286 processor, the 80287
is
wired very much
in
parallel with the 80286 CPU.
Four special status signals, PEREQ, PEACK, BUSY, and ERROR, permit the two processors to
coordinate their activities. The 80287
NPX
also monitors the 80286
Sl,
SO,
COD/INTA,
READY,
HLDA, and
CLK
pins to monitor the execution of ESC instructions (numeric instructions) by the
80286.
1-6