Presented By:
Shahnawaz Uddin
University Women’s Polytechnic AMU Aligarh
FUNDAMENTALS OF MICROPROCESSORS (WLE-203)
Unit-I: INTRODUCTION TO THE INTEL 8085
Periods / Week = 04 Total No. of Periods Reqd. = 45 Assignment + Mid Sem. = 15+25 = 40 End Sem Exam
Marks = 60 Total Marks = 100 Duration of End Sem Exam = 2.5 Hrs WLE-203: FUNDAMENTALS OF MICROPROCESSORS
Unit-I INTRODUCTION TO THE INTEL 8085 (12)
Definition of Microprocessor; Generations and Types of Microprocessors; Most Popular Microprocessors; Architecture of 8085; Brief Description of ALU, CPU, Register Section; Data
& Address Bus Time Sharing; 8085-CPU Pins and Associated Signal.
Unit-II PROGRAMMING THE 8085 (12)
Instruction; Group of Instructions; Addressing Modes of Instruction; 8085 Instruction Set;
Machine Language; Assembly Language Comparison; Assembly Language Programming (Simple Problems).
Unit-III TIMING INSTRUCTION & EXECUTION (12)
Machine Instructions: Fetch, Read, Write (IO/MEM) Cycle Timing Diagram; Interruption: Types of 8085 Interrupt System, 8085 SID and SOD lines.
Unit-IV PERIPHERAL INTERFACING (12)
PPLD’S, Brief description of 8255, 8251-USART, 8257-DMA Controller, Introduction to Intel’s 8086 microprocessor, Popular applications of Microprocessor in Industry.
BOOKS RECOMMENDED:-
1. Microprocessor Architecture, Programming and Applications with the 8085 (6th edition, 2013) by Ramesh Goankar, Penram International Publishing
2. Fundamentals of Microprocessor and Microcontrollers (2008) by B. Ram, Dhanpat Rai Publications
3. Microprocessor and Microcomputers by Rafiquzzaman 4. Introduction to Microprocessor by Mathur
Unit-I
INTRODUCTION TO THE INTEL 8085
Introduction to Microprocessor
• A microprocessor is a programmable, multipurpose, clock-driven, register-based electronic device that reads binary instructions from a storage device (memory), accepts binary data as input, process it
according to instructions and provides results as output
• In other words, Microprocessor can be assumed as the ‘brain of the microcomputer’ fabricated on a single chip and capable of processing data, controlling all of the components which make up the
microcomputer system
• Microprocessor is also used to sequence executions of instructions stored in memory, i.e., it fetches , decodes , and executes the
instructions
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Programmable Machine
• A typical programmable machine can be represented with four components: microprocessor, memory, input and output
• These four components are working together or interact with each other to perform a given task and these four components are
together called as a system
• The physical components of this system are called hardware
• A set of instructions written for the microprocessor to perform a task is called a program
• The group of programs is called a software
Fig. (1.1) A Programmable Machine
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(a) Block Diagram of a Computer
Microprocessor as a CPU (MPU)
(b) Micro Computer Block Diagram
(c) Block Diagram of a Microcontroller
Microprocessor is connected with:
• Input: It is used to give the input data to the microprocessor,
• Output: It is used to provide the result of calculations
• Memory: It is used to store the data
Microprocessor (MPU):
• A Microprocessor is a CPU on a single chip, it contains ALU, Instruction decoder, Registers, Counters, Control lines (Bus) etc.
Micro-computer (u-Computer) contains:
• A small computer
• peripheral I/O
• memory
Microcontroller (uC) contains:
• An entire computer on a single chip of silicon with some additional devices like an A/D converter, serial I/O, & timers etc.
Microprocessor as a CPU (MPU) (-contd.)
Microprocessor Vs Microcontroller
A Microprocessor:
• It has a single-chip CPU
• Bus is available
• RAM capacity
• No. of port is selectable
• RAM is larger than ROM (usually)
A Microcontroller:
• It contains a CPU and RAM, ROM, Peripherals, I/O port on a single IC
• Internal hardware is fixed
• Communicate by port
• ROM is larger than RAM (usually)
• Small power consumption
• Single chip, small board
• Implementation is easy
• Low cost
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Historical Perspective: Evolution of Microprocessor
Generations of Microprocessor
• Fair Child Semiconductors (founded in 1957) invented the first Integrated Circuit (IC) in 1959 that marked the microprocessor history
• In 1968, Gordan Moore, Robert Noyce and Andrew Grove resigned from the Fair child semiconductors and started their own company: Integrated Electronics (Intel)
• In 1971, the first microprocessor Intel 4004 was invented
• 1st Generation: This was the period during 1971 to 1973 of microprocessor’s history. In 1971, INTEL created the first microprocessor 4004 that would run at a clock speed of 108 KHz. During this period, the other microprocessors in the market including Rockwell international PPS-4, INTEL-8008 and National semiconductors IMP-16 were in use. But, all these were not TTL compatible processors.
• 2nd Generation: This was the period during 1973 to 1978 in which very efficient 8- bit microprocessors were implemented like Motorola 6800 and 6801, INTEL-8085 and Zilogs-Z80, which were among the most popular ones. Owing to their superfast speed, they were costly as they were based on NMOS technology fabrication.
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•
3rd Generation: During this period 16 bit processors were created and designed using HMOS technology. From 1979 to 1980, INTEL
8086/80186/80286 and Motorola 68000 and 68010 were developed.
Speeds of those processors were four times better than the 2nd generation processors.
•
4th Generation: From 1981 to 1995 this generation developed 32 bit
microprocessors by using HCMOS fabrication. INTEL-80386 and Motorola’s 68020/68030 were the popular processors.
•
5th Generation: From 1995 to until now this generation has been bringing out high-performance and high-speed processors that make use of 64-bit processors. Such processors include Pentium, Celeron, Dual and Quad core processors.
•
Thus, microprocessor has evolved through all these generations, and the fifth generation microprocessors represent advancement in specifications.
Generations of Microprocessor (-contd.)
•
Microprocessors are classified into five types, namely: CISC (Complex
Instruction Set Computer), RISC (Reduced Instruction Set Computer), ASIC (Application Specific Integrated Circuit) , Superscalar, DSPs (Digital Signal Processors)
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Types of Microprocessor
CISC Microprocessors
The microprocessor in which orders can be performed together along with other low level activities. These types of processors performs the different tasks like downloading, uploading, recalling data into the memory card and recalling data from the memory card. Apart from these tasks, it also does complex mathematical calculations in a single command.
RISC Microprocessors
These types of processors are made according to the function in which the microprocessor can carry out small things in specific command. In this way these processors completes more commands at a faster rate.
Superscalar Microprocessors
Superscalar processor facilitates the hardware on the processor to perform various tasks at a time. These processors can be used for ALUs or multipliers.
They have different operational units and these processors can carry out more than a one command by continuously transmitting several instructions to the extra operational units inside the processor.
Types of Microprocessor (-contd.)
Application Specific Integrated Circuit (ASIC)
The short term of Application Specific Integrated Circuit processor is an ASIC.
These processors are used for particular purposes that includes of automotive emissions control or personal digital assistant’s computer. This type of processor is made with proper specification, but apart from these it can also be made with off the shelf gears.
Digital Signal Processors (DSPs)
Digital signal processors are also called as DSP’s, these processors are used to encode and decode the videos or to convert the D/A (digital to analog) &A/D (analog to digital). They need a microprocessor that is excellent in mathematical calculations. The chips of this processor are employed in RADAR, home theaters, SONAR, audio gears, TV set top boxes and Mobile phones
There are many companies like Intel, Motorola, DEC (Digital Equipment Corporation ), TI (Texas Instruments) associated with many microprocessors such as 8085 microprocessors, ASIC, CISC, RISC, DSPs and 8086 microprocessors like Intel
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Types of Microprocessor (-contd.)
Most Popular Microprocessors
• A microprocessor is the crux of computing, that's why we have made such massive improvements to almost all of the technological advancements in the recent years.
Intel 4004:
• This particular uP was the first one to be commercially made available, it was the genesis, though it was only mediocre in terms of performance of the later uPs it was the beginning of a new era, it powered many of the scientific and military equipment more than commercial uses.
AMD Opteron :
• Similar to the intel 4004, this stepped up the uPs game to the 64-bit era which is sort of a standard now and is deemed more than necessary for even complex
calculations and analytics, till the Opteron the famous fight between Intel and AMD was about reaching the 64 bit platform.
MOS Technology 6502:
• This one was actually a clone of the Intel 8080 and didn't really technologically change the uP but what it did was it brought the uP to the common man, it was ridiculously cheap compared to 8080 and had similar features. This uP powers the Nintendo Entertainment System or the NES which gave birth to the modern video game industry and our beloved plumber “Mario”.
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AIM PowerPC :
• This is simply one of the most versatile uPs to be spawned and surprisingly not by the tech giants of Intel or AMD. These were one of the firsts to use the 32 bit architecture and were used in large numbers in many different computing devices chiefly the Apple Macintosh which in itself is a landmark in personal computing , variants of the 600 series were so good that they powered the legendary PS3 and Xbox 360 consoles opening up new markets of video gaming.
Motorola 68000:
• This was robust, backward compatible and powerful processor at the time of its launch and after a price drop literally everyone was thrusting it into their products like Apple , IBM and a large number of computer controlled appliances.
Intel Pentium Series:
• This brought the personal computers to the masses across the world , before the Pentium series the personal computer was sort of a geeky device, only enthusiasts used them and they were a luxury to have, fortunately this was the time the legendary windows 95 was released and the combination single handedly propelled the concept of a personal computer to a new dimension.
AMD K7 and Intel Pentium 4
• The AMD K7 was the first uP to hit the 1 GHz, till this point both AMD and Intel were at war as to who cracks the 1 GHz mark. This K7 was the uP that actually gave Intel a competition even briefly surpassing the Intel offering. The Intel Pentium 4 was the most widely popularised uP in the uP world. It was robust, cheap and worked perfectly with anything that developers could throw at it at that time. You can still use a P4 processor today for basic office purposes even after 16 years.
Most Popular Microprocessors (-contd.)
Zilog Z80:
• This is perhaps the most well known clone of the iconic Intel 8080 uP, the z80 was so good that it almost surpassed the 8080 itself and was used in pretty much everything from appliances to computers to toasters. There were multiple versions of the Z80 itself , cloned by Sharp, Hitachi and numerous others, it drove Japanes electronics hubs. Also, they powered the Nintendo Game Boy and many other consoles.
ARM Architecture:
• The ARM is not a processor by itself, its an architecture and manufacturers use it to make their own version of chips. This architecture powers chips that power
smartphones, iPods, mp3 players and a host of other consumer electronics, they
have solved the problem of providing acceptable level of computing with limited size like in a smartphone for example.
Intel 8080:
• This, legendary Intel 8080, gave birth to Personal Computing. The computing history books refer to this Chip as the beginning of the technical revolution in human history.
It was a remarkable 8-Bit CPU that powered the Altair 8800 , the first truly personal computer which was sold to the masses. The Motorola 6800 the Zilog Z80 are all the 8080’s children.
Most Popular Microprocessors (-contd.)
Organization of a Microprocessor Based System
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Microprocessor based System with Bus Architecture
• A simplified Microprocessor based system has been shown in fig. (1.3) which includes uP, I/O, & memory (R/W memory and ROM)
• All these components are organized around a communication path or bus
• The term peripheral is used for I/O devices
ALU (Arithmetic/Logic Unit)
• It performs such arithmetic operations as addition and subtraction, and such logic operations as AND, OR, and XOR. Results are stored either in registers or in memory.
Register Array – It consists of various registers identified by letter such as B, C, D, E, H, L, IX, and IY. These registers are used to store data and addresses temporarily during the execution of a program.
Control Unit – The control unit provides the necessary timing and control signals to all the operations in the microcomputer. It controls the flow of data between the
microprocessor and memory and peripherals.
Input – The input section transfers data and instructions in binary from the outside world to the uP. It includes such devices as a keyboard, switches, a scanner, and an analog- to-digital converter.
Output – The output section transfers data from the uP to such output devices as LED, LCD, CRT, printer, magnetic tape, or another computer.
Memory – It stores binary information as instructions and data, and provides that
information to the uP. To execute programs, uP reads instructions and data from memory and performs the computing operations in its ALU section. Results are either transferred to the output section for display or stored in memory for later use.
System Bus – It is a communication path between the microprocessor and peripherals.
The uP communicates with only one peripheral at a time. The timing is provided by the control unit of the uP.
8085 uP Model
•
A model is a conceptual representation of a real object
•
It can take many forms, such as text description, a drawing, or a built structure
•
A uP can be represented by its hardware model (physical electronic components) & a programming model (information needed to write programs)
8085 Hardware Model
•
There are two major segments in hardware model
•
In first segment there are Accumulator, ALU, Flags, Instruction decoder
•
Second segment includes 8-bit and 16-bit registers
•
Both segments are connected with various internal connections called an internal bus
•
There are three buses which are used for various interconnections: a 16- bit unidirectional address bus, 8-bit bidirectional data bus, and a control bus
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S Z AC P CY
8085 Hardware & Programming Models
(b) 8085 Programming Model (a) 8085 Hardware Model
(c) Flag Register of 8085 uP
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8085 Programming Mode
• It consist of some segments of the ALU and the registers
• This model doesn’t reflect the physical structure of 8085 uP but
includes the information that is critical in writing assembly language programs
• The model includes 6 general purpose 8-bit registers, one 8-bit
accumulator, one 8-bit flag register, & two 16-bit registers (program counter & stack pointer)
• General purpose 8-bit registers (namely A, B, C, D, E, H, & L) are
accessible to the programmer, and can be used as independent 8-bit registers or can be combined as register pairs- BC, DE, & HL: to
perform 16-bit operations depending on the particular instruction
• Accumulator (A) is used to store 8-bit data and to perform
arithmetic/logical operations and the result is stored in it after arithmetic/logical operation
8085 Hardware & Programming Models (-contd.)
•
ALU also include 5 FFs (Zero, Carry, Sign, Parity, & Auxiliary Carry), which are set or reset after an operation according to data conditions of result in
accumulator/other registers. Through software instructions, the uP uses these flags to test data conditions for decision-making process
•
16-bit program counter (PC) and stack pointer (SP) are used to hold memory addresses
•
The function of the PC is to point to the memory address from which the next instruction to be fetched/read
•
When an instruction/machine-code from the memory location is fetched, the PC is incremented by 1 to point to the next memory location
•
The SP points to a memory location in R/W memory, called the stack. The beginning of the stack is defined by loading a 16-bit address in the SP
Note: The contents of the memory address pointed to by HL could be accessed as pseudo register M
8085 Hardware & Programming Models (-contd.)
Architecture of 8085
•
The internal logic design of the uP, called its architecture, determines how
& when various operations are performed by the uP
•
The architecture of 8085 is shown in fig. (4.7), the internal architecture of 8085 includes the ALU, timing and control unit, instruction register and decoder, register array, interrupt control and serial I/O control
•
ALU: performs the arithmetic and logical operations. The operations performed by ALU of 8085 are: addition, subtraction, increment, decrement, logical AND, OR, XOR, compare, complement.
•
The accumulator and temporary register are used to hold the data during an arithmetic/logical operation
•
After an operation the result is stored in the accumulator and the flags are set or reset according to the result of the operation
•
FLAG REGISTER: There are five flags in 8085, which are:
•
sign flag (S), zero flag (Z), auxiliary carry flag (AC), parity flag (P), and carry flag (CY)
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S Z x AC x P x CY
• Apart from Accumulator (A-register), there are 6 general-purpose programmable registers B, C, D, E, H and L.
• They can be used as 8-bit registers or paired to store l6-bit data. The allowed pairs are B-C, D-E and H-L.
• STACK POINTER (SP): The stack pointer SP, holds the address of the stack top.
• PROGRAM COUNTER (PC):The program counter (PC) keeps track of program execution. To execute a program the starting address of the program is loaded in program counter.
• The temporary registers W and Z are intended for internal use of the processor and it cannot be used by the programmer.
Architecture of 8085 (-contd.)
•
BUSES: The buses are group of lines that carries data, address or control signals
•
The System Bus has multiplexed (time shared) lines, i.e., same lines are used to carry different signals
•
The CPU interface is provided to demultiplex the lines, to generate chip select signals and additional control signals
•
The system bus has separate lines for each signal
•
Address Bus: carries the address of a unique memory or input/output (I/O) device.
•
Data Bus: carries data stored in memory (or an I/O device) to the CPU or from the CPU to the memory (or I/O device)
•
Control Bus: is a collection of control signals that coordinate and synchronize the whole system
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Architecture of 8085 (-contd.)
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Fig. (4.7) The Functional Block Diagram of 8085 uP
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8085-CPU Pins and Associated Signals
8085-CPU Pins and Associated Signals (-contd.)
•
It is a 40-pin DIP chip designed using NMOS
•
ALE: It is used to separate the multiplexed Address/Data lines into lower order address line(A7-A0) and data line D7-D0
• 𝐑𝐃
: Active low, Indicates that memory device is ready to be read
• 𝐖𝐑
: Active low, Indicates that data on the data bus are ready too be written
• 𝐈𝐎/ 𝐌: Differentiate between I/O operation and memory operations
– HIGH: I/O operation is carried on
– LOW: Memory operation is carried on
•
s1, s0: These are status signals, similar to 𝐈𝐎/
𝐌, can identify various operations
•
Timing Circuit: Crystal oscillator is connected to these pins X1, X2. The 8085 uP need to be operated at 3MHz frequency, so input to X1, X2 is fed with a 6MHz frequency because the input frequency is divided by 2 internally
•
CLK OUT: The output from this port can be used as system clock for other
devices
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•
READY: When High, Microprocessor start to proceed the process provided by the Input/output devices
•
HOLD: When it is high. It means that some process is already in progress and it suspends all other process
•
HOLDA: The above status is indicated by providing HOLDA (HOLD Acknowledge) as High
• 𝐑𝐄𝐒𝐄𝐓𝐈𝐍: Reset the microprocessor. It is active low
•
RESETOUT: Output is obtained when High
•
INTR: Interrupt signal to microprocessor. It is required to provide the location of ISR (Interrupt Service Routine)
• 𝐈𝐍𝐓𝐀: when microprocessor receives an interrupt request on INTR, this is
acknowledged by sending a low signal to INTA
8085-CPU Pins and Associated Signals (-contd.)
• Power Supply and Clock Signal:
•
VCC :- Vcc is to be connected to +5V power supply.
•
Vss :- Ground reference
• X1 and X2:-
•
This pin is used for providing the clock frequency to the uP
•
Generally Crystal oscillator or LC oscillator is used to generate the frequency
•
The frequency generated here is internally divided into two
•
As we know that the basic operating timing frequency of the uP is 3 MHz so 6 MHz frequency is applied
Address Bus:
•
A8 - A15: (output; 3-state)
•
It carries the most significant 8 bits of the memory address or the 8 bits of the I/O address
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8085-CPU Pins and Associated Signals (-contd.)
Data Bus:
•
AD0 - AD7 (input/output; 3-state)
•
These multiplexed set of lines used to carry the lower order 8 bit address as well as data bus
•
During the opcode fetch operation, in the first clock cycle, the lines deliver the lower order address A0 - A7
•
In the subsequent IO / memory, read / write clock cycle the lines are used as data bus
•
The CPU may read or write out data through these lines
ALE (output) - Address Latch Enable•
It is an output signal used to give information of AD0-AD7 contents
•
It is a positive going pulse generated when a new operation is started by uP
•
When pulse goes high it indicates that AD0-AD7 are address
•
When it is low it indicates that the contents are data
8085-CPU Pins and Associated Signals (-contd.)
RD (output 3-state, active low)
•
Read memory or IO device
•
This indicates that the selected memory location or I/O device is to be read and that the data bus is ready for accepting data from the memory or I/O device
WR (output 3-state, active low)
•
Write memory or IO device
•
This indicates that the data on the data bus is to be written into the selected memory location or I/O device
IO/ M (output)
•
Select memory or an IO device
•
This status signal indicates that the read / write operation relates to whether the memory or I/O device
•
It goes high to indicate an I/O operation
•
It goes low for memory operations
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8085-CPU Pins and Associated Signals (-contd.)
Interrupts and Externally initiated operations:
• They are the signals initiated by an external device to request the uP to do a particular task or work
• There are five hardware interrupts:
• TRAP
• RST 7.5
• RST 6.5
• RST 5.5
• INTA
• Reset In (input, active low)
• This signal is used to reset the microprocessor
• The program counter inside the microprocessor is set to zero
• The buses are tri-stated
• Reset Out (Output)
• It indicates CPU is being reset
• Used to reset all the connected devices when the microprocessor is reset
8085-CPU Pins and Associated Signals (-contd.)
Main Features of INTEL 8085 are:
•
It is an 8 bit processor
•
It is as single chip NMOS device with 40 pins
•
It has multiplexed address and data bus.(AD0-AD7)
•
It works on 5-Volt dc power supply
•
The maximum clock frequency is 3-MHz while minimum frequency is 500- kHz
•
It provides 74 basic instructions (246 opcodes) with 5 different addressing mode
•
It provides 16 address lines
•
It generates 8 bit I/O address so it can access (2)
8= 256 input ports
•
It provides 5 hardware interrupts: TRAP, RST 5.5, RST 6.5, RST 7.5, INTR
•
It provides A (Accumulator), one flag register, 6 general purpose registers and two special purpose registers (SP and PC)
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Architecture of 8085 (-contd.)
• Brief Description of ALU
• Brief Description of CPU
• Brief Description of Register Section
• Data & Address Bus Time Sharing
Brief Description about 8085 uP
• 8085 Architecture consists of 5 Functional Units:
1. Arithmetic and Logic Unit (ALU):
The ALU performs the actual numerical and logic operation such as add’, ‘subtract’,
‘AND’, ‘OR’, etc. Uses data from memory and from Accumulator to perform arithmetic.
Always stores result of operation in Accumulator.
2. General Purpose Registers:
8-bit B and 8-bit C registers can be used as one 16-bit BC register pair. When used as a pair the C register contains low-order byte. Some instructions may use BC register as a data pointer.
• 8-bit D and 8-bit E registers can be used as one 16-bit DE register pair. When used as a pair the E register contains low-order byte. Some instructions may use DE register as a data pointer.
• 8-bit H and 8-bit L registers can be used as one 16-bit HL register pair. When used as a pair the L register contains low-order byte. HL register usually contains a data pointer used to reference memory addresses
• 3. Special Purpose Registers:
• a) Accumulator or A register is an 8-bit register used for arithmetic, logic, I/O and load/store operations.
• b) Flag is an 8-bit register containing 5 1-bit flags:
• Sign - set if the most significant bit of the result is set.
• Zero - set if the result is zero.
• Auxiliary carry - set if there was a carry out from bit 3 to bit 4 of the result.
• Parity - set if the parity (the number of set bits in the result) is even.
• Carry - set if there was a carry during addition, or borrow during subtraction/comparison.
• c) Stack Pointer is a 16 bit register. This register is always incremented/decremented by 2
• d) Program Counter is a 16-bit register
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Brief Description about 8085 uP
4. Instruction Register and Decoder:
Temporary store for the current instruction of a program. Latest instruction sent here from memory prior to execution. Decoder then takes instruction and
‘decodes’ or interprets the instruction. Decoded instruction then passed to next stage.
5. Timing and Control Unit: Generates signals within uP to carry out the instruction, which has been decoded. In reality causes certain connections
between blocks of the uP to be opened or closed, so that data goes where it is required, and so that ALU operations occur
Brief Description about 8085 uP
41
Operation Types in a Microprocessor
• All of the operations of the microprocessor can be classified into one of three types:
- Microprocessor Initiated Operations - Internal Operations
- Peripheral Initiated Operations
Fig. (3.1) Bus Structure of 8085 uP
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47
Memory Map and Addresses
• The memory map is a picture representation of the address range and shows where the different memory chips are located within the address range
0000
FFFF
Address Range RAM 1
RAM 2 RAM 3
RAM 4 EPROM
0000
3FFF 4400 5FFF 6000
8FFF 9000 A3FF A400
F7FF
Address Range of EPROM Chip
Address Range of 1stRAM Chip
Address Range of 2ndRAM Chip Address Range of 3rdRAM Chip
Address Range of 4thRAM Chip
• The E
CLKis divided by 2 (a 6MHz cycle take half as long a 3MHz). The reason is that the external clocks run twice as fast as a processor is because there is much data that can’t be processed in one cycle
• It also allows the supporting architecture to access the data twice as it is processed
• Think about accessing a memory slot, it would use one E
CLKcycle to locate the slot and one E
CLKcycle to write the data to the processor
• Reading memory is a very simple task, but it still take two cycles. If the E
CLKdidn’t run at twice the speed of the internal clock, the processor would be idle half of the time
Why is the clock frequency of uP is internally divided by 2?
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