2. INTERNAL 80286
Internal is a term used to describe a device that is in stalied with in the
computer
For example:
video card , internal device ,printer external device
An internal drive example for internal hard drive is any drive inside the
computer
In the pictures is an example of computer memory and example of
internal
hardward below are additional example of internal hardward in your
computer
4. Structures of 80286
It is 16 bit processor
It has 24 bit address lines
It can access 16 mb of physical memory
It is available in various versions that run on 12.5 mhz,10 MHZ
and 8 MHZ clock frequencies
80826 is upwardly compatible with 8086 in terms of instruction
set
5. The 80286 works in two operating mode,viz real address mode
Protected virtual address mode
The 80286 just acts as a fast 8086
All the memory management and protection mechanisms are
disabled in the mode
In the protected virtual address mode the 80286 works with all of
its
Memory management and protection capabilities the advanced
instruction in both the mode
6. REGISTER ORGANIZATION OF 80286
Eight 16 bit general purpose register
four 16 bit segment register
status and control register
instruction pointer
7. INTERNAL BLOCK OF 80286
The internal block of 80286 types
• Unit bus
• Address unit
• Instruction unit
• Execution unit
9. ADDRESS UNIT(AU)
It is responsible for calculating the physical address of
instruction and data that the CPU wants to access
Also the address lines derived by this unit may he used
to address
Different peripherals
This physical address computed by the address unit is
handing over to the bus unit of the CPU
10. BUS UNIT(BU)
It consists of address latches and drivers
The address latches and drivers transmit the physical
address thus formed over the address bus a0-a23
The physical address computed by the address unit is
handed over to the bus unit of the (BU)of the CPU
The bus unit also contain a bus controls module that
controls the prefetcher module
11. INSTRUCTION UNIT(IU)
These prefetched instructions are arranged in a 6 byte instructions queue
The 6 byte prefetch queue forwards the instructions arranged in it to the
instructions unit(IU)
The instruction unit accepts instruction from the prefetch queue and an
instruction decoder decodes them one by one
The decoded instruction are latched on to a decoded instruction queue
The output of the decoding circuit drives a control circuit in the execution
unit is responsible for executing the instruction received from decoded
instruction queue
12. The EU contains the register bank used for storing
the data as scratch pad or used as special purpose
register
The ALU the heart of the eu carries out all the
arithmetic and logical operation and send the result
over the data bus or back to the register bank
13. INTERRUPTS STRUCTURE OF 80286
The interrupts of 80286 may be divided into three
categories, viz.
External or Hardware interrupts.
INT instruction or software interrupts.
Interrupts generated internally by exceptions.
14. Maskable Interrupt INTR
This is a maskable interrupt input pin of which the INT type is to be
provided by an external circuit like an interrupt controller.
The other functional details of this interrupt pin are exactly similar to
the INTR input of 8086.
This interrupt is useful for troubleshooting the software.
An interrupt vector type 01 reserved for this interrupt.
Interrupt priorities
If more than one interrupt signals occur simultaneously, they are
processed according to their priorities as shown in Table.
![MICROCOMPUTER ARCHITECTURE –
INTErnal STRUCTURE OF 80286
SUBMMITED BY
R.RAMADEVI
I-MSC[CS&IT]
NSCAS](https://image.slidesharecdn.com/ppt-170830110552/85/Internal-structure-of-8086-1-320.jpg)
