80C187 datasheet(3/30 Pages) INTEL

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80C187

80C187 Data Registers

SIGN

EXPONENT

SIGNIFICAND

CONTROL REGISTER

INSTRUCTION POINTER

STATUS REGISTER

DATA POINTER

TAG WORD

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 (eg 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

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

pletely upward compatible with software for the

80868087

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

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

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

80C187 Datasheet(PDF) 3 Page - Intel Corporation

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