KU386 Datasheet, PDF (15/102 Pages) Intel Corporation – SX MICROPROCESSOR

Intel386^TM SX MICROPROCESSOR
Table 2 4 BASE and INDEX Registers for 16- and 32-Bit Addresses
16-Bit Addressing
32-Bit Addressing
BASE REGISTER
INDEX REGISTER
SCALE FACTOR
DISPLACEMENT
BX BP
SI DI
None
0 8 16-bits
Any 32-bit GP Register
Any 32-bit GP Register
Except ESP
1248
0 8 32-bits
2 5 Data Types
The Intel386 SX Microprocessor 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 Intel386
SX Microprocessor bit strings can be up to 4 giga-
bits 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 quan-
tity All operations assume a 2’s complement repre-
sentation
Unsigned Integer (Word) An unsigned 16-bit
quantity
Unsigned Long Integer (Double Word) An un-
signed 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 in-
directly 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 Alphanu-
meric or control character
String A contiguous sequence of bytes words or
dwords A string may contain between 1 byte and 4
gigabytes
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
When the Intel386 SX Microprocessor is coupled
with its numerics coprocessor the Intel387 SX then
the following common floating point types are sup-
ported
Floating Point A signed 32 64 or 80-bit real num-
ber representation Floating point numbers are sup-
ported by the Intel387 SX numerics coprocessor
Figure 2 5 illustrates the data types supported by the
Intel386 SX Microprocessor and the Intel387 SX
2 6 I O Space
The Intel386 SX Microprocessor has two distinct
physical address spaces physical memory and I O
Generally peripherals are placed in I O space al-
though the Intel386 SX Microprocessor also sup-
ports memory-mapped peripherals The I O space
consists of 64K bytes which can be divided into 64K
8-bit ports or 32K 16-bit ports or any combination of
ports which add up to no more than 64K bytes The
64K I O address space refers to physical addresses
rather than linear addresses since I O instructions
do not go through the segmentation or paging hard-
ware The M IO pin acts as an additional address
line thus allowing the system designer to easily de-
termine which address space the processor is ac-
cessing
The I O ports are accessed by the IN and OUT in-
structions with the port address supplied as an im-
mediate 8-bit constant in the instruction or in the DX
register All 8-bit and 16-bit port addresses are zero
extended on the upper address lines The I O in-
structions cause the M IO pin to be driven LOW
I O port addresses 00F8H through 00FFH are re-
served for use by Intel
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