Dept. of ElectronicsA. N. College, Patna

M. Sc. (Previous) Paper -VMicroprocessor & its Applications

Prepared by- S. P. Vats Dept. of Electronics, A. N. College, PatnaModule ContentsThe curriculum consists of 5 modules with 8085 as the main microprocessorIntroduction 8085 pins and their applications8085 Architecture & Programming8085 Interfacing TechniquesIntroduction to other 8-bit microprocessors Z80, MC6800Module I- Introduction A microprocessor is the main component of a microcomputer system and is also called as CPU (Central Processing Unit). This module is designed to give introduction to some elementary terms related to a microcomputer system. The topics covered are:Microprocessor as CPUHardware and SoftwareInput & Output DevicesMemories

Module II- 8085 PinsFor complete understanding of the interfacing circuits of memory, I/O devices etc. to the 8085 CPU it is required to learn about the functions of all the pins of 8085. The pins of 8085 are classified in following groups:Address and Data pins Control & status pinsInterrupt pinsSerial I/O pinsClock pinsReset pinsDMA pinsPower supply pins

Module III- 8085 ArchitectureTo develop programs for 8085, it is required to completely understand the internal functional blocks of 8085. 8085 architecture includes following functional blocks:8085 RegistersTiming and control unitALUInterrupt control unitSerial I/O control unitInstruction decoder & encoder unit Module III- Programming the 8085Programming of 8085 requires complete knowledge of the instruction set and its structure. This requires study of- 8085 Instruction set8085 addressing modesOne, two & three bytes instructionProgramming examples

Module IV- Interfacing TechniquesA microcomputer system consist of a minimum of memory & I/O devices. To connect these devices properly with 8085 is referred to as interfacing. This module provides interfacing techniques for-RAM & ROMI/O devicesSpecial purpose programmable devices such as 8255, 8253/8254, 8257, 8259 Module V-Introduction to other 8-bit microprocessorsThis module is designed to develop an introductory knowledge about some other 8-bit microprocessors used in embedded technology. The microprocessors covered in this module are:Z80 of ZilogMC6800 of Motorola CorporationModule IIntroduction: Microcomputer & MicroprocessorA microcomputer is a programmable machine. Modern computers are electronic and digital. The two principal characteristics of a computer are: It responds to a specific set of instructions in a well-defined manner. It can execute a prerecorded list of instructions (a program)Its main components are CPUInput & Output devicesmemory

A microprocessor is a programmable VLSI chip which controls and performs all operations in a microcomputer. Its main units are-ALURegistersControl Unit

Block diagrams (Microcomputer & Microprocessor)

Hardware All general-purpose computers require the following hardware components: Memory: Enables a computer to store data and programs.Mass storage device: Allows a computer to permanently retain large amounts of data. Common mass storage devices include disk drives and tape drives.Input device: Usually a keyboard and mouse are the input device through which data and instructions enter a computer.Output device: A display screen, printer, or other device that lets you see what the computer has accomplished.Central processing unit (CPU): The heart of the computer, this is the component that actually executes instructions.

SoftwareThe programs and data stored in a microcomputer is called as software.Programs can be written in low level languages or high level languages.A low level language can be binary language or assembly language.A CPU recognizes only binary language which is called as machine language.Assembly language instructions contain alphabets and/or numeric characters. To run assembly language programs a converter called as assembler is required.High level languages are more user friendly and contain simple words of English language. To run high level programs, converters such as compilers or interpreters are required.Input & Output DevicesInput devices are used to input electrical or physical information in a microcomputer system in digital form.In embedded applications, commonly used input devices are simple switches and sensors. In general purpose microcomputers, input devices can be keyboards, scanners, mouse etc.Output devices are used to display or perform required operation. In embedded applications commonly used output devices are LED display units, LCD display units, stepper motors etc.In general purpose computers output devices are mainly CRTs, LCD screens, LED screens, Printers etc. MemoriesMemory in a microcomputer system is used to store data and programs temporarily or permanently.The memories of primary concern for the CPU are only RAM & ROM which are called as primary memory or main memory. The CPU, at any time, only communicates with RAM & ROM.Other than primary memories, there are also secondary memories which are used for mass storage of data and programs and are transferred to the primary memory when required to be executed by the CPU. Examples of secondary memories are Hard Disks, Floppy Disks, DVDs, flash drives etc.Memory Classification

Module II-8085 pins

Pin descriptionHigher Order Address pins- A15 A8Lower Order Address/ Data Pins- AD7-AD0These are time multiplexed pins and are de-multiplexed using the pin ALE Control Pins RD, WRThese are active low Read & Write pinsStatus Pins ALE, IO/M (active low), S1, S0ALE (Address Latch Enable)-Used to de-multiplex AD7-AD0IO/M Used to select I/O or Memory operationS1,S0 Denote the status of data on data busInterrupt Pins TRAP, RST7.5, RST 6.5, RST 5.5, INTR, INTAThese are hardware interrupts used to initiate an interrupt service routine stored at predefined locations of the system memory.Serial I/O pins SID (Serial Input Data), SOD (Serial Output Data)These pins are used to interface 8085 with a serial device.

Pin Description Contd.Clock Pins- X1, X2, CLK(OUT)X1, X2- These are clock input pins. A crystal is connected between these pins such that fcrystal= 2f8085 where fcrystal= crystal frequency & f8085 = operating frequency of 8085CLK(OUT) This is an auxiliary clock output sourceReset Pins Reset In (active low), Reset OutReset In is used to reset 8085 whereas Reset Out can be used to reset other devices in the systemDMA (Direct Memory Access) pins HOLD, HLDAThese pins are used when data transfer is to be performed directly between an external device and the main memory of the system.Power Supply Pins - +VCC, VSS

Module III 8085 Architecture

8085 Architecture Contd..The Registers are of 8-bit & 16-bit size used for different purposesA- Accumulator This is an special purpose register. All the ALU operations are performed with reference to the contents of Accumulator. B,C,D,E,H,L General purpose registers. These registers can also be used for 16-bit operations in pairs. The default pairs are BC, DE & HL.F Flag register This register indicates the status of the ALU operation.PC Program Counter This is a 16-bit register used to address the memory location from where an instruction is going to be executed.SP Stack pointer - This is a 16-bit register used to address the top of the stack memory location.Temporary register, W & Z These registers are only used by 8085 and are not available for the programmer.8085 Architecture Contd..ALU Arithmetic & Logic Unit ALU of 8085 performs 8-bit arithmetic & logical operations. The operations are generally performed with Accumulator as one of the operands. The result is saved in accumulator register.Timing & Control UnitThis unit works as the brain of the CPU and generates all the timing and control signals to perform all the internal & external operations of the CPU.Instruction Decoder & Machine Cycle Encoder UnitThis unit decodes the op-code stored in the Instruction Register (IR) and encodes it for the timing & control unit to perform the execution of the instruction.

Instruction SetInstruction set of 8085 can be classified in following groups:Data Transfer InstructionsThese instructions can perform data transfer operations betweenRegisters of 8085 e.g. MOV8085 registers and main memory e.g. LDA, STA, MOV, LDAX, STAX, MVI, LXI etc.Accumulator register and I/O devices e.g. IN, OUTData transfer instructions never affect the flag bits

Instruction SetContd..Arithmetic Instructions8085 can perform only 8-bit addition, subtraction and compare operations. These operations are always performed with accumulator as one of the operands. The status of the result can be verified by the contents of the flag register.Op-codes for arithmetic instructions include ADD, ADI, ADC, ACI, SUB, SUI, SBB, SBI, CMP, CPILogical Instructions 8085 can perform 8-bit basic logical operations -AND, OR, XOR, NOT with some special operations such as rotate and shift operationsLogical instructions also modify the flag bits. Op-codes for logical instructions include ANA, ANI, ORA, ORI, XRA, XRI, CMA, RAL, RLC, RAR, RRC etc.

Instruction SetContd..Program Control InstructionsThese instructions are used to transfer the program control:to jump from one memory location to any other memory location within a programfrom one program to another program called as a subroutine8085 Instruction set consists of following program control instructions:Jump InstructionsCall & Return InstructionsRestart instructionsInstruction SetContd..Program control instructions Unconditional or ConditionalUnconditional program control instructions perform branching operation unconditionallyConditional program control instructions perform branching operation with reference to the condition of flag bits.Instruction SetContd..Unconditional Program control instructions areJMP Call & RETRST n (n=0-7)Conditional Program control instructions areJNC, JC, JNZ, JZ, JP, JM, JPE, JPOCNC, CC, CNZ, CZ, CP, CM, CPE, CPORNC, RC, RNZ, RZ, RP, RM, RPE, RPOInstruction SetContd..Machine control InstructionsThese instructions include special instructions such as HLT To halt the CPUNOP To perform no operationSIM To set the masking of hardware interrupts and serial output dataRIM To read the status of interrupt mask and serial input dataEI Enable InterruptDI Disable InterruptProgramming of 8085The following link can be used to access different type of programs.Lab ManualThe programs can be loaded and verified in the 8085 based microcomputer system available in the microprocessor lab Addressing Modes8085 instructions can be classified in following addressing modesRegister Addressing modeInstructions which have their operands in registers only e.g. MOV, ADD, SUB, ANA, ORA, XRA etc.Immediate Addressing modeInstructions in which operand immediately follows the op-code e.g. MVI, LXI, ADI, SUI, ANI, ORI etc.Direct Addressing modeInstructions have their operands in memory and the 16-bit memory address is specified in the instruction e.g. LDA, STA, LHLD, SHLD etc.Addressing Modes Contd..Register Indirect Addressing modeInstructions have their operand in memory and the 16-bit memory address is specified in a register pair e.g. LDAX, STAX, PUSH, POP etc.Implicit Addressing modeThese instruction have their operand implied in the op-code itself e.g. CMA, CMC, STC etc.

Instruction sizeAn instruction is assembled in the memory of a microcomputer system in binary form. The size of an instruction signifies how much memory space is required to load an instruction in the memory. 8085 instructions are of following sizes:One-byte Instructionse.g. MOV, ADD, ANA, SUB, ORA etc.Two-byte instructions e.g. MVI, ADI, ANI, ORI, XRI etc.Three-byte instructions e.g. LXI, LDA, STA, LHLD, SHLD etc. Module IV:Interfacing TechniquesMemory Interfacing8085 uses 16-bit memory addressing system allowing a maximum of 64 KB size of memory The logical memory address range is 0000h-FFFFhThese 64k addresses can be allotted separately to RAMs & ROMsSome interfacing circuit examples can be found in the following linkInterfacing ExamplesInterfacing Contd..I/O InterfacingTo interface Input Devices Octal buffers are used. These octal buffers are called as input ports Octal buffers contain a set of eight buffers for an 8-bit system data busA buffer is basically a current amplifier which amplifies the smaller magnitude currents of input devices before being supplied to the CPUThe tri-state logic also provides the addressing and control logic for the CPUInterfacing Contd..To interface output devices Octal Latches are used. A latch is basically a D Flip-FlopLatches are used to hold the output data because information on system data bus is available for a very small duration of time.I/O interfacing techniquesI/O structure of 8085

Interfacing Contd..There are three major types of data transfer between the microcomputer and art I/O device. They are-Programmed I/O : In programmed I/O the data transfer is accomplished through an I/O port and controlled by software. Interrupt driven I/O : In interrupt driven I/O, the I/O device will interrupt the processor, and initiate data transfer. Direct memory access (DMA) : In DMA, the data transfer between memory and I/O can be performed by bypassing the microprocessor.

Interfacing Contd..Some special purpose programmable devices used with 8085 are listed in the table of next slide.These devices are used in the system according to the requirement.Interfacing Contd..

Interfacing Contd..