· EEM332

EEM332 Mikroişlemciler: Mikroişlemciye Giriş ve Basit CPU Tasarımı

EEM332 – Mikroişlemciler · 28.10.2004 · 18.10.2026

Bu yazı, Başkent Üniversitesi EEM332 Mikroişlemciler ders arşivindeki ilgili notları ve uygulamaları bir araya getiriyor (2004–2015). Mantık devreleri, komut çevrimi, CPU birimleri ve adres, veri, kontrol yolları; farklı yılların giriş notları. Belgelerin PDF arşiv kopyaları ve varsa kaynak kodları yazının sonunda ZIP olarak indirilebilir.

CPU0_2013

EEM332

Introduction to Microprocessor Review of logic circuits

Combinational logic

Sequential logic

Finite state machine (FAM)

Memory

Microprocessor based system Instruction cycle Machine cycle

Digital circuits

Combinational circuit

Sequential Circuits

Combinational logic: Example Bir salonun bir lambası, üç giriş kapısı ve her kapının yanında, lambayı yakıp, söndürebilen bir anahtar vardır. ( 3 anahtar, bir lamba). Anahtarın ON olması (1/high) lambayı yakar (1/high), Anahtarın OFF (0/Low) olması lambayı söndürür(0 /Low) .

Devrenin çalışma şartları

1)Her 3 anahtar OFF iken lamba yanmaz. 2) Her 3 anahtar OFF iken herhangi bir

anahtar ON olursa Lamba yanar

3)Lamba yanarken ikinci anahtarın ON olması lambayı söndürür. 4)Her üç anahtar

ON iken lamba yanar

Constant switch

Analog‐Digital example

Verilen devrede G çıkışına bağlı olan alarm, s1 ve s2 algılayıcılardan gelen gerilim değerlerine bağlı olarak aktif olabilir. Alarmın aktif olması için Gnin çıkışı High olmalı., Op‐amp gerilimi: 0 ve 5 volt

Karşılaştırıcı

2.57< VS1<3.18

VS2< 0.65

Sequential logic (Flip Flop: Memory element) Input Switch : Momentary Switch

ON D-Flip Flop ile kilitleme

SET1

U2:A

74S74

R4 2

S

D Q

470 330

3 LED-RED

CLK

Q

R

LED-GREEN

10k

RESET1

OFF

Elevator Example (FSM) The elevator can be at one of two floors: Ground or First. There is one button that controls the elevator, and it has two values: Up or Down. Also, there are two lights in the elevator that indicate the current floor: Red for Ground, and Green for First. At each time step, the controller checks the current floor and current input, changes floors and lights in the obvious way. FSM diagram

State diagram

State Machines A state machine is a digital circuit composed of "n" flip‐flops that are interconnected to one another and to other inputs, with Boolean logic, in order to generate 2n internal states. The movement from one state to another is determined by a combination of the Boolean logic interconnecting the flip‐flops and the inputs to the state machine. The internal states are then decoded with additional Boolean logic to provide useful outputs at required time intervals. A counter is therefore a very simple state machine.

Memory

Access to memory

Adress, Data, control Read cycle, Write cycle

State machine and Microprocessor State machines are now most commonly used where microprocessor solutions are too expensive ( on very‐high‐volume, very‐low‐cost systems) or where it is necessary to perform very specific functions directly in hardware at a very high speed. The state machine is also of importance to us because it is really the basis of the modern microprocessor. In other words, a microprocessor is a generalised state machine that can be programmed to perform a specific sequence of functions. This is analogous to the PAL which is a generalised Boolean logic device that can be programmed to produce a required logic.

The design of state machines can become rather complex when a large number of internal states need to be produced and it is fair to say that most modern designers would prefer to apply microprocessors or Digital Signal Processors Microprocessor System: software‐programmable state machine.

In general, we refer to a microprocessor as being a single chip that is used as

the CPU of a computer or computer‐based system.

The microprocessor may be considered as a sophisticated state machine, A program instruction is nothing more than a specific bit pattern of ones and zeros that appears at the data port of the microprocessor. The state machine within the microprocessor has been designed to move from one state to another based upon those specific bit patterns.

The hardware design of the state machine within the microprocessor defines the course of events that will take place whenever a specific bit pattern arrives at the data port of the microprocessor. The hardware "programs" that are developed by the semiconductor manufacturers are known as micro‐code. Micro‐code is the lowest possible form of programming in microprocessors and it is the micro‐code that defines the characteristics of the processor that end‐users would recognise. Micro‐code is analogous to PAL programming in that it instils the logic that defines the operational sequence for a state machine and defines how it will move from one state to another, based upon bit patterns entering via the data bus.

Each cycle (tick) of the clock causes the microprocessor to jump from one internal state to another. As with other state machines, the "next state" of the microprocessor is determined by a logical combination of its current internal state, together with the condition of all the various input lines connected to it.

The microprocessor is a device composed of all the other elements of

the Combinational and Sequential logic . These elements include

State machines

Counters

Registers

Numerical circuits (Addition, Subtraction, etc ALU)

Boolean logic circuits (OR, AND, etc.)

Combinational Boolean logic.

By utilizing these elements, at each cycle of the system clock, a microprocessor can execute a very simple operation ‐ read data in; write data out; store data in an internal register; add data contained in internal registers; compare data in internal registers and so on. So, The number of bits that a microprocessor can handle as data or instructions defines the "bit‐size" of the microprocessor. Typical sizes are 8, 16, 32 and 64 bits. Since both data and program instructions appear at the data bus of the microprocessor as a collection of ones and zeros, the microprocessor cannot differentiate between them in any way other than the sequence in which they arrive.

The microprocessor

(i) It is a device based upon a state machine (ii) It contains a number of registers for temporary storage of data (iii) It contains numerical and logical circuits that can perform simple data manipulations between registers (eg: ADD, OR, etc.) (iv) It contains one input port for data (the data bus) and two output ports for data (the data bus and address bus) (v) The state machine has been designed (through micro‐coding) to respond to particular bit patterns entering the data port. The specific bit patterns are the instruction set for the microprocessor (vi) The microprocessor moves from state to state at a speed determined by a "system clock" which is generally provided by another external chip (vii) It takes one or more clock cycles to execute each instruction. The number of

clock cycles depends upon the architecture of the microprocessor (and its

micro‐coding) and the complexity of the instructions.

Points (vi) and (vii) are most important, since they are directly related to the performance of the microprocessor.

Microprocessor based system Address Bus ; Data Bus, Control Bus

CPU function is to execute (process) information stored in memory. I/O devices, such as keyboard & monitor provide a means of communicating with the

CPU.

The CPU is connected to memory and I/O through a group of wires called a bus. Allows signals to carry information from place to place.

In every computer there are three types of buses: Address bus; Data bus; Control bus.

The microcontrollers are typically used for dedicated applications such as automotive systems, home appliances,

and home entertainment systems.

A microprocessor does not know anything about "C"

or Assembly Language.

For a device (memory or I/O) to be recognized by the CPU, it must be assigned

an address.

The address assigned to a given device must be unique.

The CPU puts the address (in binary) on the address bus & decoding circuitry

finds the device.

The CPU then uses the data bus either to get data from that device or to

send data to it.

Control buses provide device read/write signals.

To indicate if the CPU is asking for, or sending information.

Adress bus

In the address bus, information transfer takes place only in one direction, from the

microprocessor to the memory or I/O elements. Therefore, this is called a unidirectional bus. This bus is typically 20 to 32 bits long. The size of the address bus determines the total number of memory addresses available in which programs can be executed by the microprocessor. The address bus is specified by the total number of

address pins on the microprocessor chip. The number of locations of memory

is equal to to 2x, where x is the number of address lines

Data bus

In the data bus, data can flow in both directions, that is, to or from the

microprocessor. Therefore, this is a bidirectional bus. In some microprocessors, the data pins are used to send other information such as address bits in addition to data. This means that the data pins are time‐shared or multiplexed. The Intel 8086 microprocessor is an example where the 20 bits of the address are multiplexed with the 16‐bit data bus and four status lines.

Control bus

The control bus consists of a number of signals that are used to synchronize the operation of the individual microcomputer elements. The microprocessor sends some of these control signals to the other elements to indicate the type of operation being performed. Each microcomputer has a unique set of control signals. However, there are some control signals that are common to most microprocessors

Microprocessor based system

For the CPU to process information, the data must be stored in RAM or ROM. The CPU cannot get the information from the disk directly because the disk is too slow. RAM & ROM are often referred to as primary memory. Disks are called secondary memory.

All common microprocessor follows this sequence

Microprocessor:??? The microprocessor is typically a single VLSI (Very Large‐Scale Integration) chip that contains all the registers, control unit, and arithmetic/ logic circuits of the microcomputer.

Machine instruction

Clock Signals

The system clock signals are contained in the control bus. These signals generate the appropriate clock periods during which instruction executions are carried out by the microprocessor. The clock signals vary from one microprocessor to another. Some microprocessors have an internal clock generator circuit to generate a clock signal.

A microprocessor chip with the main functional elements

Register Section The number, size, and types of registers vary from one microprocessor to another. However, the various registers in all microprocessors carry out similar operations. The register structures of microprocessors play a major role in designing the microprocessor architectures. Also, the register structures for a specific microprocessor determine how convenient and easy it is to program this microprocessor.

Basic Microprocessor Registers

Instruction Register (IR). The instruction register stores instructions. The contents of an instruction register are always decoded by the microprocessor as an instruction.

Program Counter (PC). The program counter contains the address of the instruction

or operation code (op‐code). The program counter normally contains the address of

the next instruction to be executed.

Upon activating the microprocessors RESET input, the address of the first instruction

to be executed is loaded into the program counter.

The program counter contents are automatically incremented by the

microprocessors internal logic.

The size of the program counter is determined by the size of the address bus.

Many instructions, such as JUMP and conditional JUMP, change the contents of the

program counter from its normal sequential address value.

Memory Address Register (MAR). The memory address register contains the address of data. The microprocessor uses the address, which is stored in the memory

address register, as a direct pointer to memory.

Accumulator (A). For an 8 bit microprocessor, the accumulator is typically an 8bit register. It is used to store the result after most ALU operations.

Control Unit The main purpose of the control unit is to read and decode instructions from the program memory. To execute an instruction, the control unit steps through the appropriate blocks of the ALU based on the op‐codes contained in the instruction register. The op‐codes define the operations to be performed by the control unit in

order to execute an instruction. The control unit interprets the contents of the

instruction register and then responds to the instruction by generating a sequence of enable signals

RESET. This input is common to all microprocessors. When this input pin is driven to HIGH or LOW (depending on the microprocessor), the program counter is loaded with a predefined address specified by the manufacturer. For example, in the 80486, upon hardware reset, the program counter is loaded with FFFFFFF0

READ/WRITE: This output line is common to all microprocessors. The status of this line tells the other microcomputer elements whether the microprocessor is performing a READ or a WRITE operation. A HIGH signal on this line indicates a READ operation and a LOW indicates a WRITE operation. Some microprocessors have separate READ and WRITE pins.

READY. This is an input to the microprocessor. Slow devices (memory and I/O) use this signal to gain extra time to transfer data to or receive data from a microprocessor. The READY signal is usually an active low signal, that is, LOW means that the microprocessor is ready

Interrupt Request (INT or IRQ). The external I/O devices can interrupt the microprocessor via this input pin on the microprocessor chip. When this signal is activated by the external devices, the microprocessor jumps to a special program, called the interrupt service routine.

Inside of Microprocessor : Arithmetic and Logic Unit (ALU)

The ALU performs all the data manipulations, such as arithmetic and logic operations, inside the microprocessor. The size of the ALU conforms to the word length of the microcomputer. This means that a 32‐bit microprocessor will have a 32‐bit ALU.

Typically, the ALU performs the following functions

Arithmetic and Logic Unit (ALU)

1. Binary addition and logic operations

2. Finding the ones complement of data

3. Shifting or rotating the contents of a general‐purpose register 1 bit to the left or

right through carry

An assembler translates a program written in assembly language into a machine language program. A compiler or interpreter, on the other hand, converts a high‐level language program such as C or C++ into a machine language program. Assembly or high level language programs are called source codes. Machine language programs are known as object codes.

To increase the programmers efficiency in writing a machine language program, hexadecimal numbers rather than binary numbers are used Assembly Language The next programming level is to use the assembly language. Each line in an assembly

language program includes four fields

1. Label field

2. Instruction,

mnemonic,

or op‐code field

3 . Operand field

4. Comment field

Assembly language

An Assembly language instruction consists of a mnemonic, optionally followed by one

or two operands.

Operands are the data items being manipulated. Mnemonics are commands to the CPU, telling it what to do with those items. Advantages of Assembly Language

1.Shows how program interfaces with the processor, operating system, and BIOS. 2.Shows how data is represented and stored in memory and on external devices. 3.Clarifies how processor accesses and executes instructions and how instructions access and process data. 4.Clarifies how a program accesses external devices.

Reasons for using Assembly Language

1. A program written in Assembly Language requires considerably less memory

and execution time than one written in a high –level language.

2. Assembly Language gives a programmer the ability to perform higly technical

tasks that would be difficult, if not impossible in a high‐level language.

3. Although most software specialists develop new applications in high‐level

languages, which are easier to write and maintain, a common practice is to recode in assembly language those sections that are time‐critical.

4. Resident programs (that reside in memory while other program execute) and

interrupt service routines (that handle input and output) are almost always develop in Assembly Language.

CPU0_2013

EEM332

Introduction to Microprocessor Review of logic circuits

Combinational logic

Sequential logic

Finite state machine (FAM)

Memory

Microprocessor based system Instruction cycle Machine cycle

Digital circuits

Combinational circuit

Sequential Circuits

Devrenin çalışma şartları

1)Her 3 anahtar OFF iken lamba yanmaz. 2) Her 3 anahtar OFF iken herhangi bir

anahtar ON olursa Lamba yanar

3)Lamba yanarken ikinci anahtarın ON olması lambayı söndürür. 4)Her üç anahtar

ON iken lamba yanar

Constant switch

Analog‐Digital example

Karşılaştırıcı

2.57< VS1<3.18

VS2< 0.65

Sequential logic (Flip Flop: Memory element) Input Switch : Momentary Switch

ON D-Flip Flop ile kilitleme

SET1

U2:A

74S74

R4 2

S

D Q

470 330

3 LED-RED

CLK

Q

R

LED-GREEN

10k

RESET1

OFF

State diagram

Memory

Access to memory

Adress, Data, control Read cycle, Write cycle

In general, we refer to a microprocessor as being a single chip that is used as

the CPU of a computer or computer‐based system.

The microprocessor is a device composed of all the other elements of

the Combinational and Sequential logic . These elements include

State machines

Counters

Registers

Numerical circuits (Addition, Subtraction, etc ALU)

Boolean logic circuits (OR, AND, etc.)

Combinational Boolean logic.

The microprocessor

clock cycles depends upon the architecture of the microprocessor (and its

micro‐coding) and the complexity of the instructions.

Points (vi) and (vii) are most important, since they are directly related to the performance of the microprocessor.

Microprocessor based system Address Bus ; Data Bus, Control Bus

CPU function is to execute (process) information stored in memory. I/O devices, such as keyboard & monitor provide a means of communicating with the

CPU.

The CPU is connected to memory and I/O through a group of wires called a bus. Allows signals to carry information from place to place.

In every computer there are three types of buses: Address bus; Data bus; Control bus.

The microcontrollers are typically used for dedicated applications such as automotive systems, home appliances,

and home entertainment systems.

A microprocessor does not know anything about "C"

or Assembly Language.

For a device (memory or I/O) to be recognized by the CPU, it must be assigned

an address.

The address assigned to a given device must be unique.

The CPU puts the address (in binary) on the address bus & decoding circuitry

finds the device.

The CPU then uses the data bus either to get data from that device or to

send data to it.

Control buses provide device read/write signals.

To indicate if the CPU is asking for, or sending information.

Adress bus

In the address bus, information transfer takes place only in one direction, from the

address pins on the microprocessor chip. The number of locations of memory

is equal to to 2x, where x is the number of address lines

Data bus

In the data bus, data can flow in both directions, that is, to or from the

Control bus

Microprocessor based system

All common microprocessor follows this sequence

Machine instruction

Clock Signals

A microprocessor chip with the main functional elements

Basic Microprocessor Registers

Instruction Register (IR). The instruction register stores instructions. The contents of an instruction register are always decoded by the microprocessor as an instruction.

Program Counter (PC). The program counter contains the address of the instruction

or operation code (op‐code). The program counter normally contains the address of

the next instruction to be executed.

Upon activating the microprocessors RESET input, the address of the first instruction

to be executed is loaded into the program counter.

The program counter contents are automatically incremented by the

microprocessors internal logic.

The size of the program counter is determined by the size of the address bus.

Many instructions, such as JUMP and conditional JUMP, change the contents of the

program counter from its normal sequential address value.

Memory Address Register (MAR). The memory address register contains the address of data. The microprocessor uses the address, which is stored in the memory

address register, as a direct pointer to memory.

Accumulator (A). For an 8 bit microprocessor, the accumulator is typically an 8bit register. It is used to store the result after most ALU operations.

order to execute an instruction. The control unit interprets the contents of the

instruction register and then responds to the instruction by generating a sequence of enable signals

Inside of Microprocessor : Arithmetic and Logic Unit (ALU)

Typically, the ALU performs the following functions

Arithmetic and Logic Unit (ALU)

1. Binary addition and logic operations

2. Finding the ones complement of data

3. Shifting or rotating the contents of a general‐purpose register 1 bit to the left or

right through carry

language program includes four fields

1. Label field

2. Instruction,

mnemonic,

or op‐code field

3 . Operand field

4. Comment field

Assembly language

An Assembly language instruction consists of a mnemonic, optionally followed by one

or two operands.

Operands are the data items being manipulated. Mnemonics are commands to the CPU, telling it what to do with those items. Advantages of Assembly Language

Reasons for using Assembly Language

1. A program written in Assembly Language requires considerably less memory

and execution time than one written in a high –level language.

2. Assembly Language gives a programmer the ability to perform higly technical

tasks that would be difficult, if not impossible in a high‐level language.

3. Although most software specialists develop new applications in high‐level

languages, which are easier to write and maintain, a common practice is to recode in assembly language those sections that are time‐critical.

4. Resident programs (that reside in memory while other program execute) and

interrupt service routines (that handle input and output) are almost always develop in Assembly Language.

CPU0_2013: sayfa 2, devre, tablo ve şekiller — CPU0_2013, sayfa 2.

CPU0_2013: sayfa 10, devre, tablo ve şekiller — CPU0_2013, sayfa 10.

CPU01_2013

EEM332 Lecture1. Design a simple CPU Read/Write Steps Machine cycle

Design a simple CPU

Instruction execution step 1: Instruction Fetch

MPU outputs value of program counter (PC) on address bus.

Memory puts contents at the instruction address on the data bus.

Instruction is stored in instruction registers (IR).

Step two: Instruction Decoder The instruction word stored in IR is

decoded by internal logic to provide

control signals to ALU and other internal circuits inside MPU. ◆ Program counter value (PC) is pushed onto the address bus, the ALU increment this value by k

and put it back into the Program
Counter.

Step 3: Operand Fetch

The instruction register provides the address of the data to be processed (i.e. operand

address).

*.Memory supplies the operand data on the data bus to the MPU, ready for processing either by the ALU or the ACC.

Step 4: Execute instruction

Processing is performed on the operand by the ALU according to the instruction. ◆ The result is put back into the Accumulator (ACC).

Step 5: Write‐back

(may not exist)

The result from the Accumulator is written back into memory.

A step‐by‐step analysis of CPU processes to add three numbers, with steps & code

shown.

Assume a CPU has registers A, B, C, and D.

An 8‐bit data bus and a 16‐bit address bus.

The CPU can access memory addresses 0000 to FFFFH.

A total of 10000H locations.

If the program to perform the actions listed above is stored in memory locations starting at 1400H, the following would represent the contents for each memory address location…

The CPU puts the address 1400H on the address bus and sends it out.Memory finds the location while the CPU activates the READ signal, indicating it wants the byte at 1400H. The content (B0) is put on the data bus & brought to the CPU.

The CPU decodes the instruction B0 with the help of its instruction decoder dictionary. Bring the byte of the next memory location into CPU Register A.

From memory location 1401H, the CPU fetches code 21H directly to Register A.After completing the instruction, the program counter points to the address of the next instruction ‐ 1402H.Address 1402H is sent out on the address bus, to fetch the next instruction

From 1402H, the CPU fetches code 04H. After decoding, the CPU knows it must add the byte at the next address (1403) to the contents of register A. After it brings the value (42H) into the CPU, it provides the contents of Register A, along with this value to the ALU to perform the addition. Program counter becomes 1404, the next instruction address

Address 1404H is put on the address bus and the code is fetched, decoded, and

executed. Again adding a value to Register A. The program counter is updated to

1406H

The contents of address 1406 (HALT code) are fetched in and executed.The HALT instruction tells the CPU to stop incrementing the program counter and asking for the next instruction. Without HALT, the CPU would continue updating the program counter

and fetching instructions.

◆ Microprocessors performs operations depending on instruction codes stored in memory.

◆ Instruction usually has two parts

❖ Opcode ‐ determines what is to be done ❖ Operand ‐ specifies where/what is the data ◆ Program Counter (PC) ‐ address of current instruction code ◆ PC incremented automatically each time it is used. ◆ The number of clock cycles taken by an instruction is the same as the number of memory access it makes. Memory contains both program and data. A peek into memory will tell you very little except a bunch of ‘1’s and ‘0’s. ◆ Program area and data area in memory are usually well separated. ◆ ALU is responsible for arithmetic and logic functions. ◆ There is always at least one register known as accumulator where the result from ALU is stored. ◆ There is usually one or more general purpose register for storing results or memory addresses. ◆ Fetching data from inside the CPU is much faster than from external memory. ◆ The processor must start from a known state. Therefore, there is always a reset signal to initialise the processor on power‐up.

A Simplified view of MPU program execution A MPU program is stored in memory as a sequence of binary values. These binary values represent instructions. Each instruction has an unique binary value. The MPU operation is controlled by reading and executing each instruction one at a time.

1. The MPU places an address on the

ADDRESS BUS.

The address is a binary value which

represents a unique

memory location.

2. The Memory places the contents of the addressed

location onto the DATA BUS. The contents is a binary value.

3. The MPU reads the binary

value from the DATA BUS.

4. The MPU interprets

what operation the BINARY Value represents and completes (executes) this operation

5. The MPU has completed its first instruction of the

program stored as binary values in the memory.

The MPU needs to be told what to do next. The next instruction is in the next memory location. Stages

1. through 4. are repeated,

Note. At Stage 1. The MPU places a new binary value onto the ADDRESS BUS. This is the memory location of the next instruction. The binary value on the ADDRESS BUS has only changed by 1.

How the MPU writes data to Memory

This instruction is

decoded as

SEND TEMP2

contents to

ADDRESS

The MPU instruction decode logic now need to execute this instruction SEND TEMP2 to an ADDRESS

TO WHAT ADDRESS …

This particular MPU instruction decodes as saying that the DESTINATION ADDRESS will be in the next memory location. The MPU then fetches the binary value from the next location, as this will be the

ADDRESS where TEMP2 contents will be SENT.

The Destination ADDRESS data has been fetched from memory and stored in a TEMP register.

The TEMP register holds the DESTINATION ADDRESS where we wish the SEND our DATA (Binary Value) which is stored in TEMP2 register.

We do not try to decode the contents of TEMP because it is not an instruction, it is data associated with a specific operation, it is known as an OPERAND

WHAT HAPPENS NEXT .. Remember we want TEMP2 contents to be sent to the MEMORY ADDRESS which is currently held in TEMP.

The contents of TEMP register are placed on the

ADDRESS BUS.

The MEMORY WRITE part of our instruction has started. In this phase, since we are sending DATA to MEMORY or WRITING TO MEMORY we must be accessing a MEMORY store which allows us to do so.

ROM is read only memory, where our program is stored, we cannot write to it. The RAM random access memory ,(read/write memory) is where our DATA will be written. Notice the control signal lines on each of the memory types.

The ADDRESS is a memory location within the RAM, the TEMP2 register places its contents onto the DATA BUS.

The RAM reads the DATA BUS value and stores it at the location which the ADDRESS value is accessing. NOTICE THE WR signal is ACTIVE

The instruction has now completed executing The result of this operation is that the contents of TEMP2 register have been WRITTEN to a RAM Memory location 11111111.

Prior to the DATA WRITE the contents of RAM location was 00001111. After the MEMORY WRITE RAM Memory location now contains 11110000 the previous DATA value has been overwritten.

A Quick Review

The MPU fetches instructions one at a time from memory The instruction is interpreted by MPU and then this operation is executed. This called the FETCH DECODE EXECUTE CYCLE. The program, sequence of instructions are held in consecutive memory locations.

We have seen that not every binary value read from memory is an instruction. Some of the values can be DATA associated with an instruction.

Read cycle (Machine cycle)

Simple Read Cycle

1. Address onto Address Bus

2. READ (RD) Control Signal Asserted by MPU

3. Data Placed from Memory onto the Data Bus

4. RD signal De-Asserted, Data into MPU temp register.

5. Read Cycle Ends

Write Cycle

1. Address placed on ADDRESS BUS

2. Data placed onto DATA BUS

3. Write (WR) Control Signal Asserted by MPU

4. Write (WR) Control Signal De-Asserted and Data

Written into Memory

5. Write Cycles completes.

Write cycle (Machine cycle)

Pipeline Timing Diagram

Figure 1‐2 Pipelined vs Nonpipelined Execution

Abstract

CPU clock frequency determines the speed of the microcomputer.

The number of data and address pins on the microprocessor chip make up the

microcomputer’s word size and maximum memory size. The microcomputer’s I/O

and interfacing capabilities are determined by the control pins on the

microprocessor chip.

The microprocessor is a single chip which is capable of processing data and

controlling all of the components which make up the microcomputer system. It contains all of the circuits needed to create the ‘brain of the microcomputer’.

1. Temporary storage locations in the form of a number

of registers which can hold binary values (information),

representing program instruction or data.

2. The Arithmetic Logic unit (ALU). This part of the MPU

performs both arithmetic and logical operations

3. Timing and Control Circuits : that keep all of the other

parts of system (memory & I/O) working together in the right time sequence.

A Bus is a common communications pathway used to carry information between

the various elements of a computer system The term BUS refers

to a group of wires or conduction tracks on a printed circuit board (PCB)

though which binary information is transferred from one part of the microcomputer

to another

Data Bus

The Data Bus carries the data which is transferred throughout the system. ( bi‐ directional)

Address Bus:

An address is a binary number that identifies a specific memory storage location or I/O port involved in a data transfer

The Address Bus is used to transmit the address of the location to the memory or the I/O port. The Address Bus is unidirectional ( one way ): addresses are always issued by the

MPU.

The Control Bus: is another group of signals whose functions are to provide synchronization ( timing control ) between the MPU and the other system components. Control signals are unidirectional, and are mainly outputs from the MPU. Example Control signals

Registers ‐ to store information temporarily. 8, 16, 32, bit, depending on CPU.

Program counter ‐ to point to the address of the

next instruction to be executed.

In the IBM PC, a register called IP or instruction pointer.

Instruction decoder ‐ to interpret the instruction

fetched into the CPU.

Bus Sizes: Buses are specified in width, number of bits. The width of the external Data bus generally gives a very good indication of the internal MPU architecture, particularly the registers size and the ALU. The Data Bus width limits the bandwidth of the data that can be transferred per bus operation.

Address Bus :

The MPU Address bus size specifies how much memory and I/O locations may accessed. Number of locations = 2N where N is number of Address lines The Address Bus may be specified using the following 16 Bits Wide, ( A15 to A0 ), 16 Address Lines : In this instance 2N = 216 = 65536 locations Microprocessors are classified by

The semiconductor technology of their design (TTL, transistor‐transistor logic;

CMOS, complementary‐metal‐oxide semiconductor; or ECL, emitter‐coupled logic),

The width of the data format (4‐bit, 8‐bit, 16‐bit, 32‐bit, or 64‐bit) they process; and

by their

instruction set (CISC, complex‐instruction‐set computer, or RISC, reduced‐

instruction‐set computer; see RISC processor). Von Neumann or Harvard (Memory usage)

What is Microprocessor ? It is a program controlled semiconductor device (IC}, which fetches,

decode and executes instructions.

What is the function of microprocessor in a system? The microprocessor is the master in the system, which controls all the activity of the system. It issues address and control signals and fetches the instruction

and data from memory. Then it executes the instruction to take appropriate
action.

What are the basic units of a microprocessor ? The basic units or blocks of a microprocessor are ALU, an array of registers and control unit. what is Software and Hardware? The Software is a set of instructions or commands needed for performing a specific task by a programmable device or a computing machine. Without software the Hardware is an idle machine.

What is assembly language? The language in which the mnemonics (short -hand form of instructions) are used to write a program is called assembly language. The manufacturers of microprocessor give the mnemonics. What are machine language and assembly language programs? The software developed using 1's and 0's are called machine language, programs. The software developed using mnemonics are called assembly language programs. What is the drawback in machine language and assembly language, programs? The machine language and assembly language programs are machine dependent. The programs developed using these languages for a particular machine cannot be directly run on another machine . Assembly language is referred to as a low‐level language because it deals directly with the internal structure of the CPU.

Define opcode and operand. Opcode (Operation code) is the part of an instruction / directive that identifies a specific operation. Operand is a part of an instruction / directive that represents a value on which the instruction acts. What is pipelined architecture?

In pipelined architecture the processor will have number of functional

units and the execution time of functional units are overlapped. Each functional unit works independently most of the time. What is fetch and execute cycle?

In general, the instruction cycle of an instruction can be divided into

fetch and execute cycles. The fetch cycle is executed to fetch the opcode from memory. The execute cycle is executed to decode the instruction and to perform the work instructed by the instruction. Assembly language is referred to as a low‐level language because it deals directly with the internal structure of the CPU.

Define machine cycle. Machine cycle is defined as the time required to complete one operation of accessing memory, I/O, or acknowledging an external request. This cycle may consist of three to six T-states. What is processor cycle (Machine cycle)? The processor cycle or machine cycle is the basic operation performed by the processor. To execute an instruction, the processor will run one or more machine cycles in a particular order. What is Instruction cycle? The sequence of operations that a processor has to carry out while executing the instruction is called Instruction cycle. Each instructioncycle of a processor indium consists of a number of machine cycles. What is opcode fetch cycle? The opcode fetch cycle is a machine cycle executed to fetch the opcode of an instruction stored in memory. Every instruction starts with opcode fetch machine cycle.

Why interfacing is needed for 1/0 devices? Generally I/O devices are slow devices. Therefore the speed of I/O devices does not match with the speed of microprocessor. And so an interface is provided between system bus and I/O devices. What is the need for Port? The I/O devices are generally slow devices and their timing characteristics do not match with processor timings. Hence the I/O devices are connected to system bus through the ports. .What is a port? The port is a buffered I/O, which is used to hold the data transmitted from the microprocessor to I/O device or vice-versa. Flip Flop: A flip‐flop stores one bit of information. Register: When a set of n flip‐flops is used to store n bits of information, such as an n‐ bit number, we refer to these flip‐flops as a register. A common clock is used for each flip‐flop in a register, shift register.:A register that provides the ability to shift its contents is called a shift register.

CPU01_2013: sayfa 2, devre, tablo ve şekiller — CPU01_2013, sayfa 2.

CPU01_2013: sayfa 3, devre, tablo ve şekiller — CPU01_2013, sayfa 3.

cpu01_08

Microprocessor based system

Address Bus

Data Bus Control Bus

The CPU is a unit that fetches and processes a set of general-purpose instructions

A microprocessor does not know anything about "C" or Assembly Language.

Microprocessor based system

Bus Arbitration

Address Bus

CPU Interrupt System Data Bus

Control Signals Status Lines

All Microcomputers consist of: Clock Power Supply

1. Microprocessor Unit (MPU)

2. Program Memory (ROM)

3. Data Memory (RAM)

4. Input / Output System

5. Bus System

(and Software)

The microprocessor is a single chip which is capable of processing data and controlling all of the components which make up the microcomputer system. It contains all of the circuits needed to create the ‘brain of the microcomputer’.

1. Temporary storage locations in the form of a number

of registers which can hold binary values (information),

representing program instruction or data.

2. The Arithmetic Logic unit (ALU). This part of the MPU

performs both arithmetic and logical operations

3. Timing and Control Circuits : that keep all of the other

parts of system (memory & I/O) working together in the right time sequence.

A Bus is a common communications pathway used to carry information between the various elements of a computer system The term BUS refers to a group of wires or conduction tracks on a printed circuit board

(PCB)

though which binary information is transferred from one part of the microcomputer to another

There are three main bus groups

1. ADDRESS BUS

2. DATA BUS

3. CONTROL BUS

Data Bus

The Data Bus carries the data which is transferred throughout the system. ( bi-directional)

Address Bus:

An address is a binary number that identifies a specific memory storage location or I/O port involved in a data transfer

The Address Bus is used to transmit the address of the location to the memory or the I/O port. The Address Bus is unidirectional ( one way ): addresses are always issued by the MPU.

Bus Sizes: Buses are specified in width, number of bits.

The width of the external Data bus generally gives a very good indication of the internal MPU architecture, particularly the registers size and the ALU.

The Data Bus width limits the bandwidth of the data that can be transferred per bus operation.

Address Bus :

The MPU Address bus size specifies how much memory

and I/O locations may accessed.

Number of locations = 2N where N is number of Address lines The Address Bus may be specified using the following 16 Bits Wide, ( A15 to A0 ), 16 Address Lines

In this instance 2N = 216 = 65536 locations

Microprocessors are classified by

The semiconductor technology of their design (TTL, transistor-

transistor logic; CMOS, complementary-metal-oxide semiconductor;

or ECL, emitter-coupled logic),

The width of the data format (4-bit, 8-bit, 16-bit, 32-bit, or 64-bit)

they process; and by their

instruction set (CISC, complex-instruction-set computer, or RISC,

reduced-instruction-set computer; see RISC processor). von Neumann or Harvard (Memory usage)

von Neumann

Harvard architecture

All common microprocessor follows this sequence

Get Instruction from memory

FETCH

Next Decode Instruction DECODE Instruction

Execute EXECUTE Instruction

Instruction Main Main Memory Memory Cycle

Control Unit Fetch 2 Decode

Execution CPU Cycle

RAM

3 Execute 4 Store

Arithmetic/Logic Unit

Includes Cache

(very fast memory)

1. The MPU places an

address on the ADDRESS
BUS.

The address is a binary value which represents a unique memory location.

2. The Memory places the contents of the addressed

location onto the DATA BUS. The contents is a binary value.

3. The MPU reads the binary

value from the DATA BUS.

4. The MPU interprets

what operation the BINARY Value represents and completes (executes) this operation

5. The MPU has completed its first instruction of the

program stored as binary values in the memory.

The MPU needs to be told what to do next. The next instruction is in the next memory location. Stages

1. through 4. are repeated,

Note. At Stage 1. The MPU places a new binary value onto the ADDRESS BUS. This is the memory location of the next instruction. The binary value on the ADDRESS BUS has only changed by 1.

How the MPU writes data to Memory

This instruction is

decoded as

SEND TEMP2

contents to

ADDRESS

The MPU instruction decode logic now need to execute this instruction SEND TEMP2 to an ADDRESS

TO WHAT ADDRESS …

This particular MPU instruction decodes as saying that the DESTINATION ADDRESS will be in the next memory location. The MPU then fetches the binary value from the next location, as this will be the

ADDRESS where TEMP2 contents will be SENT.

The Destination ADDRESS data has been fetched from memory and stored in a TEMP register.

WHAT HAPPENS NEXT ?

The TEMP register holds the DESTINATION ADDRESS where we wish the SEND our DATA (Binary Value) which is stored in TEMP2 register.

We do not try to decode the contents of TEMP because it is not an instruction, it is data associated with a specific operation, it is known as an OPERAND

WHAT HAPPENS NEXT ..

Remember we want TEMP2 contents to be sent to the MEMORY ADDRESS which is currently held in

TEMP.

The contents of TEMP register are placed on the

ADDRESS BUS.

The MEMORY WRITE part of our instruction has started. In this phase, since we are sending DATA to MEMORY or WRITING TO MEMORY we must be accessing a MEMORY store which allows us to do so.

ROM is read only memory, where our program is stored, we cannot write to it.

The RAM random access memory ,(read/write memory) is where our DATA will be written.

Notice the control signal lines on each of the memory types.

The ADDRESS is a memory location within the RAM, the TEMP2 register places its contents onto the DATA BUS.

The RAM reads the DATA BUS value and stores it at the location which the ADDRESS value is accessing. NOTICE THE WR signal is ACTIVE

The instruction has now completed executing The result of this operation is that the contents of TEMP2 register have been WRITTEN to a RAM Memory location 11111111.

Prior to the DATA WRITE the contents of RAM location was 00001111. After the MEMORY WRITE RAM Memory location now contains 11110000 the previous DATA value has been overwritten.

A Quick Review

We have seen that not every binary value read from memory is an instruction. Some of the values can be DATA associated with an instruction.

Read cycle (Machine cycle)

Simple Read Cycle

1. Address onto Address Bus

2. READ (RD) Control Signal Asserted by MPU

3. Data Placed from Memory onto the Data Bus

4. RD signal De-Asserted, Data into MPU temp register.

5. Read Cycle Ends

Write Cycle

1. Address placed on ADDRESS BUS

2. Data placed onto DATA BUS

3. Write (WR) Control Signal Asserted by MPU

4. Write (WR) Control Signal De-Asserted and Data

Written into Memory

5. Write Cycles completes.

Write cycle (Machine cycle)

Pipeline Timing Diagram

Pipeline Stages

Different architectures use different number of stages

smaller pipelines have less complexity

larger pipelines are generally faster

here, we decompose the fetch-execute cycle into 6 stages:

FI – fetch instruction

DI – decode instruction

CO – calculate operand addresses

FO – fetch operands (from registers)

EI – execute instruction (includes computing branch

results and all ALU operations)

WO – write or store result in registers (or memory)

the design of the pipeline stages has a major impact on the

architecture’s performance

Levels of Programming Languages

1) Machine Language

Consists of individual instructions that will be executed by the CPU one at

a time

2) Assembly Language (Low Level Language)

Designed for a specific family of processors (different processor

groups/family has different Assembly Language)

Consists of symbolic instructions directly related to machine language

instructions one-for-one and are assembled into machine language. ) High Level Languages

e.g. : C, C++ and Vbasic

Designed to eliminate the technicalities of a particular computer.

Statements compiled in a high level language typically generate many low-

level instructions.

Advantages of Assembly Language

1. Shows how program interfaces with the

processor, operating system, and BIOS.

2. Shows how data is represented and stored

in memory and on external devices.

3. Clarifies how processor accesses and

executes instructions and how instructions access and process data.

4. Clarifies how a program accesses external

devices.

Reasons for using Assembly Language

1. A program written in Assembly Language requires

considerably less memory and execution time than one written

in a high –level language.

2. Assembly Language gives a programmer the ability to perform

higly technical tasks that would be difficult, if not impossible in a high-level language.

3. Although most software specialists develop new applications in

high-level languages, which are easier to write and maintain, a common practice is to recode in assembly language those sections that are time-critical.

4. Resident programs (that reside in memory while other program

execute) and interrupt service routines (that handle input and output) are almost always develop in Assembly Language.

High Level Language Level Language

Assembly Language for Language for A:=B+C

Machine Code for Code for A:=B+C

Instruction Execution Cycle

The sequence of steps the processor goes through to

do the complete instruction and to get ready for the next, until the program is finished or stopped

Specific steps (simplified)

IF: instruction fetched

ID: instruction decoded, control signals asserted

RT/EX: register transfer and/or execution

PC: increment program counter

These steps are repeated for each instruction execution

cycle until the program is done, or until something is done to make the program stop

Opcodes are represented by abbreviations,

called mnemonics, that indicate the

operation. Coomon examples

ADD Add

SUB Subtract

DIV Divide

LOAD Load data from memory

STOR Store data to memory

Y = (A-B) / (C+D x E) Instruction Comment

SUB Y, A, B • Y A-B

MPY T, D, E • T DxE

ADD T, T, C • T T+C

DIV Y, Y, T • Y Y/ T

Three-address instructions

Y = (A-B) / (C+D x E)

MOVE Y, A

SUB Y, B

MOVE T, D

MPY T, E

ADD T, C

DIV Y, T

Two-address instructions

Y = (A-B) / (C+D x E) iNSTRUCTIONS Comment

LOAD D • AC D

MPY E

AC AC x E

ADD C

STOR Y

AC AC + C

LOAD A • Y AC

SUB B • AC A

DIV Y • AC AC – B

STOR Y • AC AC / Y

Y AC

One-address Instructions

The basic function as stated is to perform logic and maths operations. The Accumulator and the Flags registers play an important role in the operation of the ALU.

The Accumulator is used in all ALU operations.

The Flags or Status Register is a group of bits representing the result of the ALU operation. The Flags register contains bits such as (OV) representing an overflow flag. If the result of an

addition is greater than 255 then the OV is set to indicate

this condition. More Details to come. The type of functions performed by the ALUs of MPU

include

Addition   Shift Left Subtraction             Shift Right

Logical AND Decrement Logical OR Increment Logical XOR

What is Microprocessor ? It is a program controlled semiconductor device (IC}, which fetches, decode and executes instructions. What is the function of microprocessor in a system? The microprocessor is the master in the system, which controls all the activity of the system. It issues address and control signals and fetches the instruction and data from memory. Then it executes the instruction to take appropriate action.

In pipelined architecture the processor will have number of functional

units and the execution time of functional units are overlapped. Each functional unit works independently most of the time. What is fetch and execute cycle?

In general, the instruction cycle of an instruction can be divided into

fetch and execute cycles. The fetch cycle is executed to fetch the opcode from memory. The execute cycle is executed to decode the instruction and to perform the work instructed by the instruction.

What is the need for Port? The I/O devices are generally slow devices and their timing characteristics do not match with processor timings. Hence the I/O devices are connected to system bus through the ports. .What is a port? The port is a buffered I/O, which is used to hold the data transmitted from the microprocessor to I/O device or vice-versa.

cpu01_06

Microprocessor based system

Address Bus

Data Bus Control Bus

Bus Arbitration

Address Bus

CPU Interrupt System Data Bus

Control Signals Status Lines

All Microcomputers consist of: Clock Power Supply

1. Microprocessor Unit (MPU)

2. Program Memory (ROM)

3. Data Memory (RAM)

4. Input / Output System

5. Bus System

(and Software)

1. Temporary storage locations in the form of a number

of registers which can hold binary values (information),

representing program instruction or data.

2. The Arithmetic Logic unit (ALU). This part of the MPU

performs both arithmetic and logical operations

3. Timing and Control Circuits : that keep all of the other

parts of system (memory & I/O) working together in the right time sequence.

(PCB)

though which binary information is transferred from one part of the microcomputer to another

There are three main bus groups

1. ADDRESS BUS

2. DATA BUS

3. CONTROL BUS

Data Bus

The Data Bus carries the data which is transferred throughout the system. ( bi-directional)

Address Bus:

An address is a binary number that identifies a specific memory storage location or I/O port involved in a data transfer

The Address Bus is used to transmit the address of the location to the memory or the I/O port. The Address Bus is unidirectional ( one way ): addresses are always issued by the MPU.

1. The MPU places an

address on the ADDRESS
BUS.

The address is a binary value which represents a unique memory location.

2. The Memory places the contents of the addressed

location onto the DATA BUS. The contents is a binary value.

3. The MPU reads the binary

value from the DATA BUS.

4. The MPU interprets

what operation the BINARY Value represents and completes (executes) this operation

5. The MPU has completed its first instruction of the

program stored as binary values in the memory.

The MPU needs to be told what to do next. The next instruction is in the next memory location. Stages

1. through 4. are repeated,

Note. At Stage 1. The MPU places a new binary value onto the ADDRESS BUS. This is the memory location of the next instruction. The binary value on the ADDRESS BUS has only changed by 1.

All common microprocessor follows this sequence

Get Instruction from memory

FETCH

Next Decode Instruction DECODE Instruction

Execute EXECUTE Instruction

Instruction Main Main Memory Memory Cycle

Control Unit Fetch 2 Decode

Execution CPU Cycle

RAM

3 Execute 4 Store

Arithmetic/Logic Unit

Includes Cache

(very fast memory)

CPU Activities

CPU is in charge of the fetch-execute cycle to execute all program

instructions

This is not quite true, I/O operations are initiated by the CPU but

the actual sequence of operations is often left up to I/O modules such as I/O channels or I/O processors

Fetch-execute cycle:

Fetch instruction – CPU reads next program instruction from

memory

Interpret (decode) instruction – control unit determines what

machine actions are required including what data to fetch

Fetch data – data is fetched from memory or I/O

Process data – ALU operation or data movement

Write data – if needed, result stored in memory or I/O

Pipeline Timing Diagram

Pipeline Stages

Different architectures use different number of stages

smaller pipelines have less complexity

larger pipelines are generally faster

here, we decompose the fetch-execute cycle into 6 stages:

FI – fetch instruction

DI – decode instruction

CO – calculate operand addresses

FO – fetch operands (from registers)

EI – execute instruction (includes computing branch results and all ALU

operations)

WO – write or store result in registers (or memory)

the design of the pipeline stages has a major impact on the architecture’s

performance

How the MPU writes data to Memory

This instruction is

decoded as

SEND TEMP2

contents to

ADDRESS

The MPU instruction decode logic now need to execute this instruction SEND TEMP2 to an ADDRESS

TO WHAT ADDRESS …

This particular MPU instruction decodes as saying that the DESTINATION ADDRESS will be in the next memory location. The MPU then fetches the binary value from the next location, as this will be the

ADDRESS where TEMP2 contents will be SENT.

The Destination ADDRESS data has been fetched from memory and stored in a TEMP register.

WHAT HAPPENS NEXT ?

The TEMP register holds the DESTINATION ADDRESS where we wish the SEND our DATA (Binary Value) which is stored in TEMP2 register.

We do not try to decode the contents of TEMP because it is not an instruction, it is data associated with a specific operation, it is known as an OPERAND

WHAT HAPPENS NEXT ..

Remember we want TEMP2 contents to be sent to the MEMORY ADDRESS which is currently held in

TEMP.

The contents of TEMP register are placed on the

ADDRESS BUS.