Assembly Language Assembly Language

Lecture ByLecture ByShery khanShery khan24-25-2624-25-26

sherykhan186@gmail.comsherykhan186@gmail.comwww.sherykhan.jimdo.comwww.sherykhan.jimdo.com

AgendaAgenda

What are Real time Interrupts & Hardware What are Real time Interrupts & Hardware Interfacing?Interfacing?

What are I/O Ports?What are I/O Ports? What are IN/OUT Instruction?What are IN/OUT Instruction? What are PIC Port?What are PIC Port? What is Interrupt Chaining?What is Interrupt Chaining? What are TSR?What are TSR? Lastly we study Programmable Interval timer?Lastly we study Programmable Interval timer?

Hardware InterruptsHardware Interrupts

Single pin outside the processor Single pin outside the processor Called INT PIN that are used for External Called INT PIN that are used for External

hardware to generate Interrupthardware to generate Interrupt There are many devices that need processor There are many devices that need processor

Attention like keyboard ,Hard disk ,Floppy Attention like keyboard ,Hard disk ,Floppy Disk etcDisk etc

If processor actively monitor all devices If processor actively monitor all devices instead of being automatically interrupted instead of being automatically interrupted then Processor cant do any meaningful workthen Processor cant do any meaningful work

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Since there are many devices generating Since there are many devices generating interrupts there is going one pin inside the interrupts there is going one pin inside the processor & one pin cannot be technically processor & one pin cannot be technically derived by more than one source a controller is derived by more than one source a controller is used b/w called programmable Interrupt used b/w called programmable Interrupt controller (pic)controller (pic)

It has Eight input & single Output It has Eight input & single Output The Eight Input signal to Pic are called The Eight Input signal to Pic are called

Interrupt RequestInterrupt Request

Hardware InterruptHardware Interrupt

Hence “ A hardware Interrupt is a signal Hence “ A hardware Interrupt is a signal Received by the CPU that Tells it to Interrupt Received by the CPU that Tells it to Interrupt Its Current Sequence of Instruction &branch to Its Current Sequence of Instruction &branch to a new Location .cpu supports 256 Interrupts a new Location .cpu supports 256 Interrupts numbered 0-FF Hexa decimal “numbered 0-FF Hexa decimal “

IRQ Level: Interrupt can be triggered by a IRQ Level: Interrupt can be triggered by a number of different devices on PC .Each number of different devices on PC .Each Device has Priority based on Interrupt level Device has Priority based on Interrupt level or IRQ level . Level 0 has Highest Priorityor IRQ level . Level 0 has Highest Priority

What is IRQ????What is IRQ????

There are 8 Sources in Programmable Interrupt There are 8 Sources in Programmable Interrupt ControllerController

You See in BIOS Parallel Port IRQ 3 etcYou See in BIOS Parallel Port IRQ 3 etc These are 8 input Lines in IBM PC which ar These are 8 input Lines in IBM PC which ar

connected to Different Devices connected to Different Devices The 8 Input signal to Programmable Interrupt The 8 Input signal to Programmable Interrupt

are called IRQ Below Table is Explained are called IRQ Below Table is Explained Highest priority IRQ 0 which is TimerHighest priority IRQ 0 which is Timer IRQ 1 for Keyboard etcIRQ 1 for Keyboard etc

IRQ vs. INT MappingIRQ vs. INT Mapping

Each IRQ is Mapped to specific Interrupt in the Each IRQ is Mapped to specific Interrupt in the system This is Called IRQ & INT Mapping system This is Called IRQ & INT Mapping

IRQ 0 to 7 consecutively mapped on Int 8 to FIRQ 0 to 7 consecutively mapped on Int 8 to F This Mapping is Done by PIC not the Processor This Mapping is Done by PIC not the Processor The Actual Mechanism Fetches one Instruction from The Actual Mechanism Fetches one Instruction from

PIC whenever an INT PIN is Signaled instead of PIC whenever an INT PIN is Signaled instead of Memory Memory

We can program the pic to generate a different set of We can program the pic to generate a different set of INTERRUPT on the same Interrupt Request INTERRUPT on the same Interrupt Request

IRQ 0 is translated to INT 8IRQ 0 is translated to INT 8

Table of IRQ and InterruptsTable of IRQ and Interrupts

TableTableIRQIRQ Interrupt Interrupt

NumNumDescriptionDescription

00 88 System Timer System Timer 18.2 time/sec18.2 time/sec

11 99 KeyboardKeyboard

22 0Ah=100Ah=10 Programmable Programmable Interrupt Interrupt ControllerController

33 0Bh=110Bh=11 Serial Port 2Serial Port 2

44 0Ch=120Ch=12 Serial Port 1Serial Port 1

55 0Dh0Dh LPT2 (parallel LPT2 (parallel port 1)port 1)

66 0Eh0Eh Floppy disk Floppy disk ControllerController

77 0Fh0Fh LPT1(P P1)LPT1(P P1)

88 70h70h Real Time Real Time clockclock

99 71h71h Redirected to Redirected to INT 0AhINT 0Ah

1010 72h72h Sound cardSound card

1111 73h73h SCSI CardSCSI Card

1212 74h74h PS/2 MOUSEPS/2 MOUSE

1313 75h75h Math Math CoprocessorCoprocessor

1414 76h76h Hard disk Hard disk ControllerController

1515 77h 77h AvailableAvailable

PriorityPriority

IRQ 0 the Highest Priority Interrupt is IRQ 0 the Highest Priority Interrupt is generated by the Timer chip frequency and generated by the Timer chip frequency and Handler at INT 8 is Invoked which Update the Handler at INT 8 is Invoked which Update the the System Time.the System Time.

A key Press generated IRQ 1 and the INT 9 A key Press generated IRQ 1 and the INT 9 handler is invoked which store this Keyhandler is invoked which store this Key

What is IRQ Conflict???What is IRQ Conflict???

When Network Card and Sound Card is Fit in When Network Card and Sound Card is Fit in the Motherboard of the System and Connected the Motherboard of the System and Connected to Processor through IRQ 5 both have Same to Processor through IRQ 5 both have Same IRQ at that Situation when 2 outputs sources IRQ at that Situation when 2 outputs sources drive one Input source then we say that IRQ drive one Input source then we say that IRQ conflict conflict

Working /Mechanism of IRQ & EOIWorking /Mechanism of IRQ & EOI

when a key is Pressed IRQ 1 is generated and INT 9 when a key is Pressed IRQ 1 is generated and INT 9 Handler which stores the key .Handler which stores the key .

When an Interrupt comes Outside the Processor or When an Interrupt comes Outside the Processor or From a Device it Reaches to PIC as then Processor From a Device it Reaches to PIC as then Processor and Processor Invoke the software related routine and Processor Invoke the software related routine now this Routine is working after some time it Tells now this Routine is working after some time it Tells to PIC that I finish my work so we Acknowledge the to PIC that I finish my work so we Acknowledge the PIC BY END OF INTERRUPT so that the Switches PIC BY END OF INTERRUPT so that the Switches which are Open that they Closed and Other Waiting which are Open that they Closed and Other Waiting Interrupts Are Come that Processor Serve Them Interrupts Are Come that Processor Serve Them

I/O PORTSI/O PORTS

Around the Processor the Different Devices Around the Processor the Different Devices like Printer , Video , Keyboard Port ,etc like Printer , Video , Keyboard Port ,etc

How the Processor Communicate with these How the Processor Communicate with these Devices if Processor Don’t Communicate with Devices if Processor Don’t Communicate with These Devices don’t send or Receive data then These Devices don’t send or Receive data then there no function is performed . there no function is performed .

So the Processor must Communicate with So the Processor must Communicate with these Devices these Peripheral Devices are these Devices these Peripheral Devices are called I/O PORTS called I/O PORTS

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Processor Communicate with Peripheral Processor Communicate with Peripheral devices is Similar as it can Communicate with devices is Similar as it can Communicate with MEMORY MEMORY

Similar to Memory Operation it can Similar to Memory Operation it can Either Read or Write .Either Read or Write . Some thing is Happen when Processor Read or Some thing is Happen when Processor Read or

Write on I/O PORTS Write on I/O PORTS

Separation of Peripheral address Separation of Peripheral address &Memory Address Space &Memory Address Space

IBM PC or IAPX 8088 Processor Separate IBM PC or IAPX 8088 Processor Separate Peripheral Address space from the Memory Peripheral Address space from the Memory Address Space Address Space

Another Concept is there Another Concept is there

MEMORY MAPPED I/O: Designated Memory MEMORY MAPPED I/O: Designated Memory cell Work as a Port for specific devices . (wo cell Work as a Port for specific devices . (wo input devices jo memory address ka ander hi input devices jo memory address ka ander hi periphiral adress ko bhe rakhta hain)periphiral adress ko bhe rakhta hain)

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Processor see only Data Bus & Address Bus Processor see only Data Bus & Address Bus Iapx8088 divides in two parts Iapx8088 divides in two parts First is MEMORY Operation (Move is Valid)First is MEMORY Operation (Move is Valid) Secondly one Signal tells that at this Particular Secondly one Signal tells that at this Particular

time what was the Interest of Processor time what was the Interest of Processor whether it is Interested in Outside World I/O whether it is Interested in Outside World I/O Ports or whether it is Interested in Memory Ports or whether it is Interested in Memory world world

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For this Purpose it uses a number which is on For this Purpose it uses a number which is on Address Bus that Tells the Interest of Address Bus that Tells the Interest of Processor Processor

Iapx 8088 uses a PIN we called as I/O by Iapx 8088 uses a PIN we called as I/O by n n bar bar

When this PIN is Level 0 processor Access Memory When this PIN is Level 0 processor Access Memory When this Pin is Level 1 it can Access I/o portWhen this Pin is Level 1 it can Access I/o port Basically the num is on Address bus which indicate Basically the num is on Address bus which indicate

that it is of I/O world or Memory world that it is of I/O world or Memory world

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Read & write operation are performed by using same Read & write operation are performed by using same data Bus and Address bus data Bus and Address bus

PIN I/O by n bar Differentiate that from which world PIN I/O by n bar Differentiate that from which world data is expected data is expected

So by this way it can read or write the Peripheral So by this way it can read or write the Peripheral Register Register

The I/O space is of 16 bits which mean 64 K The I/O space is of 16 bits which mean 64 K Different I/O ports connect to it Different I/O ports connect to it Which we say that 65536 I/O PORTS are connected Which we say that 65536 I/O PORTS are connected

to Processor to Processor

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Keyboard is mapped to I/O ports in this I/o Keyboard is mapped to I/O ports in this I/o space space

PIC is mapped , sound card etc ………PIC is mapped , sound card etc ……… There are port address through which There are port address through which

communication is done communication is done

IN /OUT INSTRUCTIONIN /OUT INSTRUCTION

There are two special instruction for read and There are two special instruction for read and write I/o ports write I/o ports

For read we use IN (port to processor)For read we use IN (port to processor) For Write we use OUT (processor to port)For Write we use OUT (processor to port) When we use IN/out instead of MOV the When we use IN/out instead of MOV the

Processor Automatically indicate I/O by n bar Processor Automatically indicate I/O by n bar Indicate that it is read or Write from I/O portIndicate that it is read or Write from I/O port There are also two variant in BYTE & WORDThere are also two variant in BYTE & WORD

Address of the PortsAddress of the Ports

Port 21 is for PIC (Prog Interrupt controller)Port 21 is for PIC (Prog Interrupt controller) Port 61 is for Keyboard Port 61 is for Keyboard Port 378 H is for Parallel Port so on……..Port 378 H is for Parallel Port so on…….. IN: in this Instruction we use a destination Register in IN: in this Instruction we use a destination Register in

which data comes while read from port to processor which data comes while read from port to processor in Byte case we use ALin Byte case we use AL

In Word case we AXIn Word case we AX Port address is not in segment and Offset form Port address is not in segment and Offset form It is Just a NUM and it is Destination so it is DX It is Just a NUM and it is Destination so it is DX

registerregister

ContinueContinue If the port num is less than 255 or it can fit in 8 bit so If the port num is less than 255 or it can fit in 8 bit so

we cannot use DX or not store in DX register it is we cannot use DX or not store in DX register it is written directly in instructionwritten directly in instruction

Port num tells us that at some particular time Port num tells us that at some particular time Processor talk to which specific device/ portProcessor talk to which specific device/ port

IN : we can first read and then fetched so register is IN : we can first read and then fetched so register is first written first written

OUT: at there the data is written on port so the the OUT: at there the data is written on port so the the destination is port so port number is first written in destination is port so port number is first written in the instruction the instruction

All the Rules of MOV instruction are followed All the Rules of MOV instruction are followed ………………

Sample Sample

Lecture 25Lecture 25

Keyboard Controller:Keyboard Controller: Keyboard is the collection of labeled button Keyboard is the collection of labeled button

and every button is designated a number (not and every button is designated a number (not the AscII Code)the AscII Code)

The number is send to the processor when the The number is send to the processor when the Key is Pressed from this number called Scan Key is Pressed from this number called Scan Code the processor understand which Key was Code the processor understand which Key was Pressed Pressed

Scan Code Scan Code For Each Key Scan Code comes Twice once the Key press and For Each Key Scan Code comes Twice once the Key press and

once for key release once for key release Both Scan code are differ in one bit Both Scan code are differ in one bit The lower seven bit contain the key number The lower seven bit contain the key number While the Most Significant bit is clear in the Press code and While the Most Significant bit is clear in the Press code and

Set in the Release Code Set in the Release Code If we write Capital A so we First Press Shift Key the Scan If we write Capital A so we First Press Shift Key the Scan

Code is Sent then We Pressed A Scan Code is Sent then the Code is Sent then We Pressed A Scan Code is Sent then the Release code of A & release code of Shift Key and Interrupt Release code of A & release code of Shift Key and Interrupt Handler Understand That Sequence Should Result in ASCII Handler Understand That Sequence Should Result in ASCII Code of ACode of A

Interrupt handler REMEMBER the Sequence .Interrupt handler REMEMBER the Sequence .

Keyboard PortKeyboard Port

The Keyboard Port is 60 the Keyboard The Keyboard Port is 60 the Keyboard Generate IRQ 1 when Ever Key is Pressed so Generate IRQ 1 when Ever Key is Pressed so if we Hooked INT 9 inside the it read Port if we Hooked INT 9 inside the it read Port 60so we can tell Which Key is Pressed 60so we can tell Which Key is Pressed

Scan code table is Given Below Scan code table is Given Below

Scan code Scan code KEYSKEYS Scan CodeScan Code

11 7878

22 7979

33 7A7A

44 7B7B

55 7C7C

66 7D7D

77 7E7E

88 7F7F

99 8080

1010 8181

SCAN CODESCAN CODE

KEYKEY SCAN CODESCAN CODE

AA 1E1E

BB 3030

CC 2E2E

DD 2020

EE 1212

FF 2121

GG 2222

HH 2323

II 1717

SCAN CODESCAN CODE

KEYKEY SCAN CODESCAN CODE

JJ 2424

KK 2525

LL 2626

MM 3232

NN 3131

OO 1818

PP 1919

QQ 1010

RR 1313

SCAN CODESCAN CODE

KEYSKEYS SCAN CODESCAN CODE

SS IFIF

TT 1414

UU 1616

VV 2F2F

WW 1111

XX 2D2D

YY 1515

ZZ 2C2C

SCAN CODESCAN CODE

KEYSKEYS alonealone With CTRL KEYWith CTRL KEY

HOMEHOME 4747 7777

ENDEND 4F4F 7575

Page upPage up 4949 8484

PageDownPageDown 5151 7676

Left arrowLeft arrow 4B4B 7272

Right ArrowRight Arrow 4D4D 7373

uparrowuparrow 4848 7474

Dn arrowDn arrow 5050

insertinsert 5252

USING SCAN CODE PROGRAMUSING SCAN CODE PROGRAM

in al,0x60 ;Keyboard Portin al,0x60 ;Keyboard Port cmp al,0x47……………HOME KEY cmp al,0x47……………HOME KEY jne nextcmpjne nextcmp

nextcmp:nextcmp: cmp al,0x4B ;Left arrow …………..LEFT cmp al,0x4B ;Left arrow …………..LEFT jne nomatch jne nomatch

THAT’S PROGRAM THAT’S PROGRAM [org 0x0100][org 0x0100] jmp startjmp start keyboardISR:keyboardISR: push axpush ax push espush es mov ax,0xb800mov ax,0xb800 mov es,axmov es,ax in al,0x60 ;Keyboard Port……………………………..in al,0x60 ;Keyboard Port…………………………….. cmp al,0x47……………………………………………..cmp al,0x47…………………………………………….. jne nextcmpjne nextcmp mov byte [es:0],'H'mov byte [es:0],'H' jmp nomatchjmp nomatch nextcmp:nextcmp: cmp al,0x4B ;Left arrow………………………………………..cmp al,0x4B ;Left arrow……………………………………….. jne nomatchjne nomatch mov byte [es:0],'L'mov byte [es:0],'L'

continuecontinue nomatch:nomatch: mov al,0x20mov al,0x20 out 0x20,alout 0x20,al pop espop es pop axpop ax iretiret start:start: xor ax,axxor ax,ax mov es,axmov es,ax clicli mov word [es:9*4],keyboardISRmov word [es:9*4],keyboardISR mov [es:9*4+2],csmov [es:9*4+2],cs stisti li:li: mov ah,0mov ah,0 int 0x16int 0x16

Lecture 26Lecture 26Basic OS UnderstandingBasic OS Understanding

In MS DOS Memory point of View we see In MS DOS Memory point of View we see first IVT then Os Different Things Appearfirst IVT then Os Different Things Appear

Then BIOS Data Area , Dos Data Area ,IO.sys Then BIOS Data Area , Dos Data Area ,IO.sys

Then MS Dos.sys and Device driver are loaded Then MS Dos.sys and Device driver are loaded

Then the MS Dos Command Interpreter is Then the MS Dos Command Interpreter is Loaded Loaded

Lastly the area which is Free for us called Lastly the area which is Free for us called Transient Program Area Transient Program Area

What is Meant For Transient????What is Meant For Transient????

We say this Area Transient because in this Area our We say this Area Transient because in this Area our Programs are loaded ,Executed and after there Programs are loaded ,Executed and after there Specific Work the Free this Area so that this Area is Specific Work the Free this Area so that this Area is Utilized by other program so that it is Called Utilized by other program so that it is Called Transient Area .Transient Area .

Mechanism :Dos maintain a Pointer which is called Mechanism :Dos maintain a Pointer which is called Free Mem from where the TPA is Started it Dos Free Mem from where the TPA is Started it Dos Pointer is Started and Remember the Position and it is Pointer is Started and Remember the Position and it is Own word to the RAM 640 K it is there Own word to the RAM 640 K it is there

Free Min Pointer Working Free Min Pointer Working

When Ever a program is Loaded to this When Ever a program is Loaded to this Memory the Free Min Pointer gives a Control Memory the Free Min Pointer gives a Control to Program when the Program Executed to Program when the Program Executed Finishes the Last to lines 4c Terminator Lines Finishes the Last to lines 4c Terminator Lines Return the Control to Free min Pointer And Return the Control to Free min Pointer And FREED the Space of TPA FREED the Space of TPA

Legal control return to DOS Legal control return to DOS

TerminationTermination

One way is to Freed all Memory and Return Control One way is to Freed all Memory and Return Control to Dos and Free Min Pointer is Start Pointing start of to Dos and Free Min Pointer is Start Pointing start of the TPA the TPA

Second way is that Free Min Pointer Stop Second way is that Free Min Pointer Stop Deallocation at some point were I say and some Part Deallocation at some point were I say and some Part of Program is Retain in this memory and make it Part of Program is Retain in this memory and make it Part of OS .or Some part of Program Resident at there of OS .or Some part of Program Resident at there leave the some part of program in this Memory . leave the some part of program in this Memory . Termination is Done Control Return but some Part of Termination is Done Control Return but some Part of Program Remain there and Pointer start Pointing after Program Remain there and Pointer start Pointing after that ………….that ………….

TSR TSR

Terminate & stay Resident :above the Terminate & stay Resident :above the Phenomena is Explain is Called TSR Phenomena is Explain is Called TSR

Control Return to DosControl Return to Dos Some Part Is Remain There in we say ResidentSome Part Is Remain There in we say Resident We say it is Extension of Command Prompt We say it is Extension of Command Prompt

and Not Over written from There Free Min and Not Over written from There Free Min Pointer is Starting New Programs are Executed Pointer is Starting New Programs are Executed after my Resident Programafter my Resident Program

How Much memory we Can How Much memory we Can Resident???Resident???

We Can Resident Memory in Multiples of We Can Resident Memory in Multiples of 16Byte we say that 32 byte,48,64 16Byte we say that 32 byte,48,64

These are in paragraph which is chunk of 16 These are in paragraph which is chunk of 16 Bytes and its Multiples Bytes and its Multiples

Labeling is Done when we Resident Labeling is Done when we Resident RoundUp is Done And Calculation is RoundUp is Done And Calculation is Label Offset +15/16=round up Label Offset +15/16=round up We know that 4 shift right is equal to division We know that 4 shift right is equal to division

of 16 so we use SHR while Doing Round UP of 16 so we use SHR while Doing Round UP

Programmable Interval TimerProgrammable Interval Timer PIT is Important Peripheral Device chip numbered is 8254 PIT is Important Peripheral Device chip numbered is 8254 Chip has Fixed Frequency 1.1938 MHZ Chip has Fixed Frequency 1.1938 MHZ Inside the chip 16 Bit Divisor which Divide the Input Inside the chip 16 Bit Divisor which Divide the Input

Frequency and output is Connected to IRQ 0 line of PIC Frequency and output is Connected to IRQ 0 line of PIC 0 means a divisor of 65536 0 means a divisor of 65536 1193180/65536=18.2 timer per sec this is called Timer TICK 1193180/65536=18.2 timer per sec this is called Timer TICK In one Sec 55 ms times a IRQ 0 is Coming so these Timer In one Sec 55 ms times a IRQ 0 is Coming so these Timer

Tick Are Counted and IBM PC maintain His TIME Tick Are Counted and IBM PC maintain His TIME

THAT’S ALLTHAT’S ALL

THANKS FOR LISTENING ME THANKS FOR LISTENING ME FEED BACKS FEED BACKS sherykhan186@gmail.comsherykhan186@gmail.com www.sherykhan.jimdo.comwww.sherykhan.jimdo.com www.skvu.blogspot.comwww.skvu.blogspot.com RESPECT YOUR PARENTS ………….RESPECT YOUR PARENTS …………. ALLAH HAFIZ ALLAH HAFIZ