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EIE311 The microprocessor and its architecture

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LIC : Dr. Jimmy To. JT/YHC/EIE311/2002/CSF_ch2.ppt. page 2. Introduction ... and stack segment loaded into a DOS system memory. Figure 2.5 DOS system memory ... – PowerPoint PPT presentation

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Title: EIE311 The microprocessor and its architecture


1
EIE311The microprocessor and its architecture
LIC Dr. Jimmy To
2
Introduction
  • This chapter presents the microprocessor as a
    programmable device by first looking at its
    internal programming model and then at how it
    addresses its memory space.

3
Internal microprocessor architecture
  • Before a program is written or any instruction
    investigated, the internal configuration of the
    microprocessor must be known.
  • The programming model of the 8086 through the
    Pentium Pro is considered program visible because
    its registers are used during programming and
    specified by the instructions.
  • Registers which can not be addressable directly
    during applications programming but may be used
    indirectly during system programming are
    considered program invisible.

4
Internal microprocessor architecture
  • Figure 2.1 illustrates the programming model of
    the 8086 through the Pentium II microprocessor.
  • Some registers are general-purpose or
    multipurpose registers, while some have special
    purposes.

5
Registers
  • Registers hold various data sizes (bytes, words,
    or doublewords) and are used for almost any
    purpose as dictated by a program.
  • Multipurpose Registers
  • Special-purpose Registers
  • Segment Registers

6
Real mode memory addressing
  • Real mode operation allows the microprocessor to
    address only the first 1M byte of memory space -
    even the Pentium microprocessor.
  • The first 1M byte of memory is called either the
    real memory or conventional memory system.
  • Real mode operation allows application software
    written for the 8088/8086, which contain only 1M
    byte of memory, to function in the 80286 and
    above without changing the software.
  • In all cases, each of these microprocessors
    begins operation in the real mode by default
    whenever power is applied or the microprocessor
    is reset.

7
Segments and offsets
  • A combination of a segment address and an offset
    address access a memory location in the real
    mode.
  • The segment address, located within one of the
    segment registers, defines the beginning address
    of any 64K-byte memory segment.
  • The offset address selects any location within
    the 64K-byte memory segment.
  • Figure 2.3
  • Table 2.1

8
Segments and offsets
  • A 20-bit real mode address allows one to access
    the start of a segment at any 16-byte boundary
    within the first 1M byte of memory.
  • Any real mode segments can only begin at a
    16-byte boundary in the memory system and this
    boundary is often called a paragraph.
  • In the 80286 (with special external circuitry)
    and the 80386 through the Pentium Pro, an extra
    64K minus 16 bytes of memory is addressable when
    the segment address is FFFFH and the HIMEM.SYS
    driver is installed in the system.
  • This area of memory (0FFFF0H-10FFEFH) is referred
    to as high memory.

9
Default segment and offset registers
  • The microprocessors has a set of rules that apply
    to segments whenever memory is addressed.
  • These rules, which apply in either the real or
    protected mode, define the segment register and
    offset register combination used by certain
    addressing modes.
  • Table 2.2

10
Default segment and offset registers
  • The code segment register defines the start of
    the code segment and the instruction pointer
    locates the next instruction within the code
    segment.
  • Stack data are references through the stack
    segment at the memory location addressed by
    either the stack pointer (SP/ESP) or the base
    pointer (BP/EBP).
  • Table 2.3

11
Default segment and offset registers
  • One can think of segments as windows that can be
    moved over any area of memory to access data and
    code.
  • A program can have a lot of segments, but can
    only access four (in 8086-80286) or six (in 80386
    and above) segments at a time.
  • Figure 2.4
  • Figure 2.5

12
Relocation
  • Segment and offset addressing scheme allows
    relocation.
  • A relocatable program is one that can be placed
    into any area of memory and executed without
    change.
  • Relocatable data are data that can be placed in
    any area of memory and used without any change to
    the program.

13
Figure 2.1 programming Model
Figure 2.1 The programming model of the Intel
8086 through the Pentium II.
14
Figure 2.3 Real Mode Memory
Figure 2.3 The real mode memory-addressing
scheme, using a segment address plus an offset.
15
Table 2.1 Example segment addresses
16
Table 2.2 Default Segment and Offset Registers
Table 2.2 8086-80486 and Pentium-Pentium II
default 16-bit segment and offset address
combinations.
17
Table 2.3 Default Segment and Offset Registers
Table 2.3 80386, 80486, Pentium, Pentium Pro, and
Pentium II default 32-bit segment and offset
address combinations.
18
Figure 2.4 A Memory System
19
Figure 2.5 DOS system memory
Figure 2.5 An application program containing a
code, data, and stack segment loaded into a DOS
system memory.
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