The document discusses microprocessors and interrupts in computer systems. It describes how the first microprocessor was developed by Intel and Busicom in 1971. It then covers several Intel microprocessor models from the 4004 to the 8088 and beyond. The document also defines interrupts as signals that cause the CPU to pause its current task and service the interrupt. It distinguishes between maskable, non-maskable, software, and hardware interrupts and provides examples of each. Finally, it discusses the different software interrupts available in the 8085 microprocessor.

1. Computer organization & architecture
Interrupt signals and working(8085
or 8086)

2.  What is a microprocessor?
 What are its functions?
 How was it invented?
 Read on to know about one of the greatest
wonder of electronics.

3.  A microprocessor is an electronic component
that is used by a computer to do its work. It
is a central processing unit on a single
integrated circuit chip containing millions of
very small components.
 Everything a computer does is described by
lots of precise instructions, and
microprocessors carry out these instructions
at incredible speed—many millions of times a
second.

4.  Single board micro computers
 Personal Computers
 Communication
 Instrumentation
 Control
 Office Automation and Publication
 Among others.

5.  The world's first microprocessor, the 4004,
was co-developed by Busicom, a Japanese
manufacturer of calculators, and Intel, a U.S.
manufacturer of semiconductors

6.  Intel 4004 (4 bit microprocessor and it was not a
powerful microprocessor)
 Intel 8080 (was the first microprocessor to make
it to Home computers, It was introduced during
the year 1974 and it could perform 8 bit
operations)
 Intel 8085 (Came out in the year 1976, it was an
update of 8080 processors.
 Intel 8086 (Came out during the year 1976. The
major difference between 8085 and 8086
processor is that 8085 is an 8 bit processor, but
8086 processor is a 16 bit processor.

7.  Intel 8087
 Intel 8088 processor ( It was the first to be
incorporated into IBM personal computers)
 As the years progressed lots of processors
from 8088,80286,80386,80486,Pentium II,
Pentium III, Pentium IV and now
Core2Duo,Dual Core and Quad core
processors are the latest in the market.

8.  Apart from Intel, there are some other
manufacturers who produce Microprocessor
chips. Such manufacturers are called second
source manufacturers.
 The second source manufacturers include:
 AMD
 Mitsubishi
 NEC
 OKI
 Toshiba
 Siemens

9.  In year 1976, Intel introduced the 8085
microprocessor.
 the 8085 microprocessor is an update of 8080
processors.
 8080 processors are updated by adding two
Enable/Disable Instructions, Three added
interrupt pins and serial I/O pin
 Intel introduced 8086 pins during the year 1976.
The major difference between 8085 and 8086
processor is that 8085 is an 8 bit processor, but
8086 processor is a 16 bit processor.

10. An interrupt is a signal or condition
that causes the executing program to
stop, save its state, and do a function
call to service the signal or condition.

11.  Once the servicing is complete, the service
routine does a return from interrupt sequence,
effectively a return from function call, that
allows the processor to continue doing what it
was doing before the interrupt.

12.  Maskable interrupts.
 non-maskable interrupts.

13.  Difference between maskable and non-maskable
interrupt?
 the interrupt which can be ignored by the
processor ,while performing its operations are
called maskable interrupts
 Non-maskable interrupts do not get gated by the
interrupt control register -- they ALWAYS
interrupt, no matter what state your processor is
in. Typically these are used for CRITICIAL or
FATAL conditions, or for system reset functions.
If your system gets stuck in an infinite loop with
interrupts disabled, the NMI is your last hope to
reset the system.

14.  Software interrupts.
 Hardware interrupts.

15.  Interrupt generated by executing an
instruction is called software interrupt. It's
also called 'trap'. Software interrupts are
generally used to make system calls i.e. to
request operating system to perform an I/O
operation or to run a new program.

16.  Examples:
C++:
A cout or cin statement would generate a
software interrupt because it would make a
system call to print something.
 A fork() statement in Linux would generate a
software interrupt because it would make a
system call to create a new process.
 Assembly IA32:
The instruction int 21h would generate a
software interrupt which would request
something from operating system (depending on
the register values).

17.  Hardware interrupts are generated by
hardware devices when something unusual
happens; this could be a keypress or a mouse
move or any other action.

19.  • People like connecting devices
 • A computer is much more than the CPU
 • Keyboard, mouse, screen, disk drives
 • Scanner, printer, sound card, camera, etc.
 • These devices occasionally need CPU service
 • But we can’t predict when
 • External events typically occur on a
macroscopic
 timescale
 • we want to keep the CPU busy between events
 FNeed a way for CPU to find out devices need
 attention

20. They are
 TRAP
 RST 7.5
 RST6.5
 RST5.5
 INTR
 INTA

21.  A software interrupts is a particular instructions
that can be inserted into the desired location in
the rpogram. There are eight Software interrupts
in 8085 Microprocessor. From RST0 to RST7.
 RST0
 RST1
 RST2
 RST3
 RST4
 RST5
 RST6
 RST7

22.  They allow the microprocessor to transfer
program control from the main program to
the subroutine program. After completing the
subroutine program, the program control
returns back to the main program.

23.  TRAP:-It is non maskable edge and level
triggered interrupt. TRAP has the
highest priority and vectores interrupt. Edge
and level triggered means that the TRAP must
go high and remain high until it is
acknowledged. In case of sudden power
failure, it executes a ISR and send the data
from main memory to backup memory.

24.  RST7.5:-It has the second highest priority. It
is maskable and edge level triggered
interrupt. The vector address of this interrupt
is 003CH. Edge sensitive means input goes
high and no need to maintain high state until
it is recognized.

25.  RST6.5 and RST5.5:-These are level triggered
and maskable interrupts.
 .INTR:-It is level triggered and maskable
interrupt. It has the lowest priority. It can be
disabled by reseting the microprocessor or by
DI and SIM instruction.

26.  We can calculate the vector address of these
interrupts using the formula given below:

 Vector Address = Interrupt
Number * 8
 So we can find simply vector address. For Example:


RST2: vector address=2*8 = 16
 RST1: vector address=1*8 = 08
 RST3: vector address=3*8 = 24