376 datasheet(14/95 Pages) INTEL

14 / 95 page

376 EMBEDDED PROCESSOR

GENERATING 16-BIT ADDRESSES

The 80376 executes code with a default length for

operands and addresses of 32 bits The 80376 is

also able to execute operands and addresses of 16

bits This is specified through the use of override

prefixes Two prefixes the Operand Length Prefix

and the Address Length Prefix override the de-

fault 32-bit length on an individual instruction basis

These prefixes are automatically added by assem-

blers The Operand Length and Address Length Pre-

fixes can be applied separately or in combination to

any instruction

The 80376 normally executes 32-bit code and uses

either 8- or 32-bit displacements and any register

can be used as based or index registers When exe-

cuting 16-bit code (by prefix overrides) the displace-

ments are either 8 or 16 bits and the base and index

trates the differences

Table 24 BASE and INDEX Registers for 16- and 32-Bit Addresses

16-Bit Addressing

32-Bit Addressing

BASE REGISTER

BX BP

Any 32-Bit GP Register

INDEX REGISTER

SI DI

Any 32-Bit GP Register

except ESP

SCALE FACTOR

None

1 2 4 8

DISPLACMENT

0 8 16 Bits

0 8 32 Bits

25 Data Types

The 80376 supports all of the data types commonly used in high level languages

Bit

A single bit quantity

Bit Field

A group of up to 32 contiguous bits which spans a maximum of four

bytes

Bit String

A set of contiguous bits on the 80376 bit strings can be up to 16 Mbits

long

Byte

A signed 8-bit quantity

Unsigned Byte

An unsigned 8-bit quantity

Integer (Word)

A signed 16-bit quantity

Long Integer (Double Word)

A signed 32-bit quantity All operations assume a 2’s complement

representation

Unsigned Integer (Word)

An unsigned 16-bit quantity

Unsigned Long Integer

(Double Word)

An unsigned 32-bit quantity

Signed Quad Word

A signed 64-bit quantity

Unsigned Quad Word

An unsigned 64-bit quantity

Pointer

A 16- or 32-bit offset only quantity which indirectly references another

memory location

Long Pointer

A full pointer which consists of a 16-bit segment selector and either a

16- or 32-bit offset

Char

A byte representation of an ASCII Alphanumeric or control character

String

A contiguous sequence of bytes words or dwords A string may

contain between 1 byte and 16 Mbytes

BCD

A byte (unpacked) representation of decimal digits 0 – 9

Packed BCD

A byte (packed) representation of two decimal digits 0 – 9 storing one

digit in each nibble

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