80C187 Datasheet, PDF(3/30 Page) Intel Corporation

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80C187 Datasheet, PDF (3/30 Pages) Intel Corporation – 80-BIT MATH COPROCESSOR

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80C187

80C187 Data Registers

64 63

SIGN

EXPONENT

SIGNIFICAND

CONTROL REGISTER

STATUS REGISTER

TAG WORD

INSTRUCTION POINTER

DATA POINTER

Figure 2 Register Set

FUNCTIONAL DESCRIPTION

The 80C187 Math Coprocessor provides arithmetic

instructions for a variety of numeric data types It

also executes numerous built-in transcendental

functions (e g tangent sine cosine and log func-

tions) The 80C187 effectively extends the register

and instruction set of the 80C186 CPU for existing

data types and adds several new data types as well

Figure 2 shows the additional registers visible to pro-

grams in a system that includes the 80C187 Essen-

tially the 80C187 can be treated as an additional

resource or an extension to the CPU The 80C186

CPU together with an 80C187 can be used as a sin-

gle unified system

CPU automatically controls the 80C187 whenever a

numerics instruction is executed All physical memo-

ry and virtual memory of the CPU are available for

storage of the instructions and operands of pro-

grams that use the 80C187 All memory addressing

modes are available for addressing numerics oper-

ands

The end of this data sheet lists by class the instruc-

tions that the 80C187 adds to the instruction set

NOTE

The 80C187 Math Coprocessor is also referred to

as a Numeric Processor Extension (NPX) in this

document

A 80C186 system that includes the 80C187 is com-

pletely upward compatible with software for the

8086 8087

The 80C187 interfaces only with the 80C186 CPU

The interface hardware for the 80C187 is not imple-

mented on the 80C188

PROGRAMMING INTERFACE

The 80C187 adds to the CPU additional data types

registers instructions and interrupts specifically de-

signed to facilitate high-speed numerics processing

All new instructions and data types are directly sup-

ported by the assembler and compilers for high-level

languages The 80C187 also supports the full

80387DX instruction set

All communication between the CPU and the

80C187 is transparent to applications software The

Data Types

Table 1 lists the seven data types that the 80C187

supports and presents the format for each type Op-

erands are stored in memory with the least signifi-

cant digit at the lowest memory address Programs

retrieve these values by generating the lowest ad-

dress For maximum system performance all oper-

ands should start at even physical-memory address-

es operands may begin at odd addresses but will

require extra memory cycles to access the entire op-

erand

Internally the 80C187 holds all numbers in the ex-

tended-precision real format Instructions that load

operands from memory automatically convert oper-

ands represented in memory as 16- 32- or 64-bit

integers 32- or 64-bit floating-point numbers or 18-

digit packed BCD numbers into extended-precision

real format Instructions that store operands in mem-

ory perform the inverse type conversion

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