Intel 80287, 80286 manual Hardware Interface, Numeric Data Types

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	-2X109 ::S X::s +2X109
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 10.37 ::s1 X I::s 3.37X1038
Long real'	64	15-16	4.19X 10.307 ::S I X I ::S 1.67X 10308
Temporary real	80	19	3.4 X 10.4932 ::S I X I ::S 1.2 X 104932

	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, 2x -1, Y·Log2(X + 1), Y·Log2(X)
Constants	0, 1, 71", Log,02, Log.2, Log2 10, Log2e
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.

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