1 1 What Is Microprocessor Microprocessor is a

(1. 1) What Is Microprocessor ? • Microprocessor is a multipurpose, programmable, clock-driven, register based electronics device which accept binary data as a input and process that data according to the instruction and give results as output.

Types of Microprocessor Year Word Size Memory Capacity 4004 1971 4 -bit 1 KB 8080 1973 8 -bit 64 KB 8085 1976 8 -bit 64 KB 8086 1978 16 -bit 1 MB 80286 1982 16 -bit 16 MB Pentium 1993 64 -bit 4 GB Pentium Pro 1995 64 -bit 64 GB P-III 1999 64 -bit 64 GB

8085 INTRODUCTION 8085 consists of various units and each unit performs its own functions. The various units of a microprocessor are listed below Ø Accumulator Ø Arithmetic and logic Unit Ø General purpose register Ø Program counter Ø Stack pointer Ø Temporary register

Ø Flags Ø Instruction register and Decoder Ø Timing and Control unit Ø Interrupt control Ø Serial Input/output control Ø Address buffer and Address-Data buffer Ø Address bus and Data bus

Pin Diagram of 8085

8085 PIN DESCRIPTION Some important pins are : Ø AD 0 -AD 7: Multiplexed Address and data lines. Ø A 8 -A 15: higher order address lines. Ø ALE: used to demultiplex data bus and low order address bus. Ø S 0, S 1: status signals used to indicate type of operation. Ø RD¯: active low input signal read data from I/O device or memory. Ø WR¯: active low output signal write data on memory or an I/O device.

Ø READY: It is used for synchronization. Ø TRAP: highest priority non mask able interrupt , vectored interrupt address 0024 H. Ø RST 5. 5, 6. 5, 7. 5: maskable interrupts, vectored interrupt low priority than TRAP Address: RST 7. 5 003 CH RST 6. 5 0034 H RST 5. 5 002 CH Ø INTR¯&INTA: maskable interrupt, non vectored interrupt Address provided by external hardware. Ø IO/M¯: I/O mode(IO/M¯=1) or Memory mode(IO/M¯=0 )

Ø HOLD&HLDA: release the control of buses HLDA is the acknowledgement signal for that. Ø RESET IN¯: This is input signal. When RESET IN¯ is low µp restarts and starts executing from location 0000 H. Ø SID: Serial input data Ø X 1 X 2 : These are clock input signals. Ø VCC&VSS: VCC=+ 5 Volt & VSS=GND

(1. 2) 8085 OPERATIONS 1. Microprocessor initiated operation Ø Ø Memory read Memory write I/O read I/O write

8085 OPERATIONS 2. Internal Data Manipulation Ø Ø Ø Store 8 -bit data Perform arithmatic & Logical operation Test for certain condition Sequence the execution of Instructions Store data temporary in stack during execution

8085 OPERATIONS 3. Externally Initiated Operation Ø Ø Reset Interrupt Ready Hold

(1. 3)8085 ARCHITECTURE

(1. 4)Registers of 8085

(1. 5)FLAG REGISTER S Z - AC - P - S: Sign flag 1=Negative 0=Positive Z: Zero flag is set when result of an operation is 0. Ac: set when carry generated from lower nibble to higer nibble P: Parity flag is set when result contains even number of 1’s. CY: Carry flag is set when there is carry generated by an operation. Rest are don’t care flip flops. CY

(1. 6)TYPES OF INTERRUPT Ø An interrupt is considered to be an emergency signal. • • • TRAP RST 7. 5 RST 6. 5 RST 5. 5 INTR

SERIAL I/O • SOD • SID

(1. 7)BUS ORGANISATION • There are three buses in microprocessor • Address bus: 1)16 bit 2)Unidirectional 3)direction(MPU to EXTERNAL device) • Data bus: 1)8 bit 2)Bidirectional • Control bus

BUS STRECTURE

De multiplexing of buses

• AD 7 –AD 0 is connected as inputs to the latch 74 LS 373. • The ALE signal is connected to the enable (G) pin of the latch and the OC –Output control – of the latch is grounded • When ALE is high it consider address and when ALE is low it consider as data.

(1. 8)Clock speed • Microprocessor works on clock speed of 3 MHz frequency