1. COURSE OUTCOMES OF Microprocessor and programming
Describe the architecture and organization of microprocessor along with instruction set format.
C404.2
Describe modes and functional block diagram of 8086 along with pins and their functions
C404.3
List and describe memory and addressing modes
C404.4
List, describe and use different types of instructions, directives and interrupts
C404.5
Develop assembly language programs using various programming tools.
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2. C404.1
Describe the architecture and organization of microprocessor along with instruction set format.
C404.2
Describe modes and functional block diagram of 8086 along with pins and their functions
C404.3
List and describe memory and addressing modes
C404.4
List, describe and use different types of instructions, directives and interrupts
C404.5
Develop assembly language programs using various programming tools.

3. Chapter 2
16 BIT MICROPROCESSOR 8086

4. Features of 8086 microprocessor
16 bit microprocessor
20 address lines i.e 2^20=1MB memory addressed.
16 bit address and data bus multiplexed i.e AD0-AD7 to minimize no of pin on IC
Clock frequency between 5Mhz-10Mhz
Arithmetic operation on 8 bit or 16 bit signed or unsigned data including multiplication 7 division.
Operate in single processor or multiprocessor
Instruction set-> powerful->flexible.
256 interrupt
Operate in max& min mode to achieve high performance
Support multiprogramming
Separate instruction set for string manipulation.

5. Architecture of 8086 microprocessor

6. Architecture of 8086 It is divided into 2 parts
1) Bus interface unit (BIU)
2) Execution unit (EU)
Bus Interface unit :=
It acts as interface between system bus and the execution unit.
Fetches instruction from memory.
Reads data from I/O ports and memories.
Writes data to ports and memories
Supports pipelining.
BIU handles transfer of data on all the buses for the execution unit.
Blocks of BIU:=
Queue=
To speed up the program execution BIU fetches as many as 6 instruction bytes from memory .
These pre-fetched instruction byte for execution unit in FIFO group of registers called a QUEUE.

7. Concept of pipelining:=
fetching the next instruction while recent instruction executes is known as pipelining. 6 5 4 3 2 1 I1 I2 I3 I4 I5 I6 I7 I8 I9 1 2 3 4 5 6 7 8 9
Clock cycle F I1 I2 I3 I4 I5
F-Fetch D I1 I2 I3 I4
D-Decode
E-Executes E I1 I2 I3
Clock cycle
Fig: pipelined execution of 3 instruction 1 2 3 4 5

8. On non pipelined processor 9 clock cycle are required for individual fetch , decode & execute for 3 instruction.
On pipelined processor fetch, decode & execute operation are performed in parallel.
-only 5 cycle are required to execute 3 instruction.
- 1 instruction requires -> 3 cycle to completes.
Additional instruction complete at rate of one per cycle.
During clock cycle 5 I3 instruction executing , I4 is decoding , I5 instruction fetched.
If 1000 instruction it requires 3000 clock cycle on non pipelined processor.----> require 1002 clock cycle on pipelined processor.
In 8086 performs fetch , decode , & executes instruction in parallel.

9. The BIU contain 4 16 bit segment registers
it hold upper 16 bit of starting address of 4 memory segment that 8086 is working with particular time .
Es hold upper 16 bits of starting address of extra segment
Cs hold upper 16 bits of starting address of code segment
Ss & Ds hold upper 16 bit of starting address of stack segment & data segment. ES
Segment Register CS SS DS
Instruction pointer IP
3) Instruction Pointer Register (IP) :=
- Ip register hold 16 bit address of next code byte within code segment . It contain offset from base address to next instruction byte to be fetched

10. Execution Unit
The execution unit of 8086 informs BIU of address of instruction & data needed for execution &execute it.

11. Functional block of EU 1) Control circuit ,instruction decoder , ALU
The execution unit contain control circuit that direct all internal operation.
The execution unit has 16 bit ALU block that perform arithmetic & logical operation like +, - , *,AND , OR ,NOT
The instruction decoder in EU that translates the instruction fetch from memory into a series of action that EU carried out.

12. 8086/88 internal registers 16 bits (2 bytes each)
AX, BX, CX and DX are two
bytes wide and each byte can
be accessed separately
These registers are used as
memory pointers.
Flags will be discussed later
Segment registers are used
as base address for a segment
in the 1 M byte of memory

13. -The execution unit has 8 general purpose register labeled as AH,AL,BH,BL,CH,CL,DH,DL
These register can be used for temporary storage of 8 bit data & 16 bit data
AH-AL pair is referred as AX , BH- BL pair is referred as BX , CH-CL pair is referred as CX , DH-DL pair is referred as DX.
1) Stack pointer register:
It contain a 16 bit offset added to stack segment register indicates address of memory location when word was most recently stored.
Base pointer register:
The base pointer register can be used instead of stack pointer register to access memory location within the stack
The 20 bit address can be obtained by shifting the contents of the stack segment by 4 bits & adding the contents of BP to it

14. 3) Source index register:
The source index register is used to load 16 bit offset of a data word in data segment .
The physical address of the data word can be obtained by shifting the contents of DS register by 4 bits & adding into SI
4) Destination index register
It is used to hold the 16 bit offset of a data word in extra segment while executing string instruction
The 20 bit physical address is calculated from DS & DI

16. Multiplexed address & data pin
Multiplexed address & status pins
Select Minimum/ maximum mode
Multplexed address and data bus
Interrupt Pins

17. 8086 operates into 2 modes
1) minimum mode
2) Maximum mode
The following pins are important in both minimum & maximum mode
CLK( pin no-19)
The maximum clock frequency 5-10MHZ
Provides basics timing for processor & bus controller.
It is symmetric square wave with 33% duty cycle.
2) Vcc (pin no-40)
Provide +5v power supply pin
3) GND (pin no-1,20)
Ground for internal circuit

18. 4) RESET (pin no-21)
It is a system reset
When this signal goes high ,processor enter into reset state &terminate the current activity & start execution from FFFF0H
Active high signal - for at least 4 clock cycle.
5) AD0-AD15
These lines are multiplexed ,bi-directional address / data bus
8086 has 20 bit address bus( A0-A19)
16 bit data bus
During t1 cycle  carry lower order 16 bit address
T2,t3,t4 - carry 16 bit data
So AD0-AD7 lines carry lower order byte of data& AD8 –AD15 carry high order byte of data

19. 6) A19/s6 , A18/s5 , A17/s4 , A16/s3
These lines are multiplexed address & status lines
Upper 4 bits address sent on this lines for memory operation
During I/O operation these lines are low
During memory & I/O operation status information is availble on these lines in T2,T4 cycles.
status of interrupt flag indicated by S5
S S segment Register
alternate data
stack
code
Data
7) BHE /S7 (pin no- 34) - bus high enable / status
During t1 state BHE signal is used to enable dat on most signficant half of data bus pins D15- D8..S7 status information availble during t2,t3,t4 status - remain high

20. BHE A word /byte access
whole word from even address
upper byte from / to odd address
lower byte from / to even address
none
8) RD (pin no-32)
Active low signal
Read strobe indicates that processor is performed memory, I/O read cycle depending on s2 pin
9) Ready (pin no-22)
When high-- carry out it normal operation
When low - freezes it’s bus & enters a wait state -

21. 10) INTR (pin no-18) Interrupt request
High level triggered interrupt request i/p
Checked last clock to check availability of request
If request is not occurred ,processor enters interrupt acknowledge cycle
11) TEST (pin no-23)
This i/p is examined by 8086 wait instruction
If TEST i/p  low - execution continued -- if not then processor enter /wait in idle state
12) NMI (pin no-17) Non mask able interrupt
NMI is not mask able internally by software
A transition from low- high initiates the interrupt at the end of current instruction
It is edge triggered i/p interrupt causes type-2 interrupt

22. MN / MX
Pin indicates the operating mode of 8086
There are 2 modes of OS i.e maximum and minimum modes
MN/MX - high 8086 operating in -- minimum mode
MN/MX - low 8086 operating in -- maximum mode

23. Signal description pins for minimum mode :=
M/IO (pin no-28) status line:-
This signal is used to distinguish between memory access & I/O access
2) WR (pin no-29) Write:-
This signal indicates that processor is performing a memory write depending on the state of M/IO signal
3) INTA (pin no-24) interrupt acknowledge
-used as an active low interrupt acknowledge signal
It is used as a read strobe for interrupt acknowledge cycle
4) ALE (pin no-25) address latch enable
- High  8086 indicates ADDR1 DATA & ADDR/STATUS bus
High pulse active - during t1 state of bus cycle
5) DT /R (pin no-27) data transmit/receive
-these signal used to decide direction of data flow through the transceivers 8286/8287

24. -processor send data out -- signal high
Processor receives data --- signal low
6) DEN (pin no-26) data enable
- Signal provides an output enables signal for transceivers 8286 / 8287
7) HOLD
Active high i/p signal
8) HLDA
- Active high o/p signal

25. * Signal description of pins for maximum mode:=
Qs1 ,Qs0 (pin no-24,25) queue status
Qs Qs features
no operation
first byte of opcode from queue
empty the queue
subsequent byte from queue
LOCK (pin no-24)
Active low signals indicates that other system bus masters are not to gain control of system while lock is active low.
lock is activated by lock prefix instruction & remain active until completion of next instruction.

26. Interrupt Acknowledge 1 I/O read I/O write Halt Op-code Fetch
3) S0, S1, S2
- Are status lines which indicate the type of operation, being carried out by processor. S2 S1 S0
Status
Interrupt Acknowledge 1
I/O read
I/O write
Halt
Op-code Fetch
Memory Read
Memory Write
Passive

27. 4) RQ/GT0, RQ/GT1 (Request/Grant)
Are used by other local bus masters, in max mode, to force the processor to release the local bus at the end of the processor’s current bus cycle.

30. Memory Address Generation
Intel
Memory Address Generation
The BIU has a dedicated adder for determining physical memory addresses
Offset Value (16 bits)
Segment Register (16 bits)
Adder
Physical Address (20 Bits)

31. Byte
Top of Stack
end of code segment
6FFFF
SP = FFE0
6FFE0 H
Physical address
0123
Start of stack segment
60000 H
SS: 60000 +
SP: FFE0 =
Physical address FFE0
Physical Address generation for stack segment

32. 8284 Pin Diagram:

33. 8284 Block Diagram: x1 AEN1 CSYNC F / C Clock OSC Clock Logic x2 EF1
PCLK
RDY1
AEN1
Ready Logic
READY
RDY2
AEN2
Reset Logic
RESET
RES

34. 8086 System Minimum mode
(74LS373)
(74LS245)

35. Processor Timing Diagram of 8086 (Minimum Mode) for Memory or I/O Read
CLOCK __
DT/R
ALE
AD15 - AD0
A15 - A0
D0 – D15 (from memory)
A19/S6 - A16/S3
A19 - A16
S6 - S3 __
IO/M
if I/O ACCESS this is HIGH, if MEMORY ACCESS this is LOW
____ RD
______
DEN

36. Processor Timing Diagram of 8086 (Minimum Mode) for Memory or I/O Write
CLOCK __
DT/R
ALE
AD15 - AD0
A15 - A0
D15 - D0 (from memory)
A19/S6 - A16/S3
A19 - A16
S6 - S3 __
IO/M
if I/O ACCESS this is HIGH, if MEMORY ACCESS this is LOW
____ WR
______
DEN

37. 8086 System Maximum Mode

38. Processor Timing Diagram of 8086(Maximum Mode) for Memory or I/O Read
CLOCK __
DT/R
ALE
D0-D15
AD15- AD0
A15 - A0
S2-S0
S2-S0 Active
S2-S0 Inacive
A19/S6 - A16/S3
A19 - A16
S6 - S3
MDRC/IORC
______
DEN

39. Processor Timing Diagram of 8086(Maximum Mode) for Memory or I/O Write
CLOCK __
DT/R
ALE
D0-D15
AD15- AD0
A15 - A0
S2-S0
S2-S0 Active
S2-S0 Inacive
A19/S6 - A16/S3
A19 - A16
S6 - S3
MWTC &IOWC
AMWC/AIOWC
______
DEN
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