1. 8085 – Processor, Architecture & Pin Diagram

2. EE8551- Microprocessor and Microcontroller V- Semester EEE Mr. Hariharan N M.E. Assistant Professor Department of Electrical and Electronics Engineering R M K College of Engineering and Technology

3. EE8551- Microprocessor and Microcontroller Unit –I 8085 PROCESSOR

4. Syllabus UNIT I 8085 PROCESSOR Hardware Architecture, pinouts – Functional Building Blocks of Processor – Memory organization – I/O ports and data transfer concepts– Timing Diagram – Interrupts.

5. 0 A computer Input deviceOutput device Memory Processor

6. Processor… Processor ALU Control Unit Register Array

7. UNIT 18085 processor 7 Hardware Architecture, pinouts Functional Building Blocks of Processor Memory organization I/O ports and data transfer concepts Timing Diagram Interrupts.

8. 8085 Microprocessor - Architecture

9. 8 bit internal bus ACC TEMP ALU FLAG Reg BC DE HL Stack pointer Program Counter Incrementer/ Decrementer Addr.Latch Instruction Reg. Instruction Decoder and Machine Cycle Encoding Timing and Control Addr. Bus Add/Data Bus A8 – A15 AD0 – AD7 Interrupt Controller Serial I/O Control TRAP RST 7.5 RST 6.5RST 5.5INTRSID SOD X1 X2 Register Array

10. 10 8085 PIN DIAGRAM

12. PIN CONFIGURATION 12

13. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 X1 X2 Reset out SID SOD TRAP RST 7.5 RST 6.5 RST 5.5 INTR AD7 AD6 AD5 AD4 AD3 AD2 AD1 AD0 GND Crystal Oscillators Serial Ports Interrupts Multiplexed Bus Address Bus or Data bus A15 A14 A13 A12 A11 A10 A9 A8 High order Address Bus VCC +5V Power Supply S0 ALE S1 HOLD CLK out DMA Signals 8085 8085 PIN Diagram

14. 8085 Processor - Features The salient features of 8085 μp are:  It is a 8 bit microprocessor.  It is manufactured with N-MOS technology.  It has 16-bit address bus and hence can address up to 216= 65536 bytes  (64KB) memory locations through A0 –A15.  The first 8 lines of address bus and 8 lines of data bus are multiplexed AD0 – AD7.  Data bus is a group of 8 lines D0 - D7  It supports external interrupt request.  A 16 bit program counter (PC)  A 16 bit stack pointer (SP)  Six 8-bit general purpose register arranged in pairs: BC, DE, HL.  It requires a signal +5V power supply and operates at 3.2 MHZ single phase clock.  It is enclosed with 40 pins DIP (Dual in line package).

15. 8 bit internal bus ACC TEMP ALU FLAG Reg BC DE HL Stack pointer Program Counter Incrementer/ Decrementer Addr.Latch Instruction Reg Instruction Decoder and Machine Cycle Encoding Timing and Control Addr. Bus Add/Data Bus A8 – A15 AD0 – AD7 Interrupt Controller Serial I/O Control TRAP RST 7.5 RST 6.5RST 5.5INTRSID SOD X1 X2

16. 8 bit internal bus ACC (8) ACC (8) TEMP ALU Accumulator: (A reg.)  It is an 8-bit register used to perform arithmetic, logical, I/O & LOAD/STORE operations.  It is connected to the internal data bus & ALU. ALU:  The 8085A has a simple 8 bit ALU  As the name suggests, it performs arithmetic and logical operations like Addition, Subtraction, AND, OR, etc. on 8-bit data.  It works in coordination with the accumulator, temporary register, five flags, and arithmetic and logic circuits. Temporary register:-  It is an 8-bit register, which holds the temporary data of arithmetic and logical operations.

17. 8 bit internal bus ACC (8) ACC (8) TEMP ALU FLAG Reg D7D6D5D4D3D2D1D0 SZACPCY Carry Flag Carry(CY)- If the result stored in an accumulator generates a carry in its final output then it is set otherwise it is reset. The carry flag also serves as a borrow flag for subtraction 11110101 01000101 F5 45 13A 00111010 111 1 1 Flag Register 1 Parity (P)-If the no of 1’s is even in the output stored in the accumulator then it is set otherwise it is reset for the odd.

18. 8 bit internal bus ACC (8) ACC (8) TEMP ALU FLAG Reg D7D6D5D4D3D2D1D0 SZACPCY Carry Flag 11110101 01001011 F5 4B 140 01000000 111 1 1 1 Flag Register 0 1 Auxiliary Carry Flag 1 1 0 0 Auxiliary carry (AC)-If any carry goes from D3 to D4 in the output then it is set otherwise it is reset. 1 Zeros (Z)-If the result stored in an accumulator is zero then this flip flop is set otherwise it is reset. Sign(S)- If D7 of the result is 1 then sign flag is set otherwise reset. As we know that a number on the D7 always decides the sign of the number. if D7 is 1: the number is negative. if D7 is 0: the number is positive.

19. 8 bit internal bus General-purpose register:- There are 6 general-purpose registers in 8085 processor, i.e. B, C, D, E, H & L. Each register can hold 8-bit data. These registers can work in pairs to hold 16-bit data and their pairing combination is like B-C, D-E & H-L. Stack pointer Stack pointer:- It is also a 16-bit register that works like a stack, which is always incremented/decremented by 2 during push & pop operations. Program Counter Program counter:- It is a 16-bit register used to store the memory address location of the next instruction to be executed. Microprocessor increments the program whenever an instruction is being executed so that the program counterpoints to the memory address of the next instruction that is going to be executed Incrementer/ Decrementer Addr.Latch B C D E H L

20. 8 bit internal bus BC DE HL Addr. Bus Add/Data Bus A8 – A15 AD0 – AD7 ADDRESS BUS:  The address bus is a group of 16 lines generally identified as A0 to A15.  The address bus is unidirectional i.e. bits flow in one direction from MPU to peripheral devices.  The 8085 MPU with its 16 address lines is capable of addressing 2 16 = 65,536(64K) bytes memory location. Stack pointer Program Counter Incrementer/ Decrementer Addr.Latch DATA BUS:  The data bus is a group of 8 lines used for data flow. These lines are bi-directional i.e. data flow in both direction between MPU and peripheral devices.  The 8 data lines enable the MPU to manipulate 8bit data ranging from 00 to FF (2 8 = 256 numbers). The largest number that can appear on the data bus is 11111111(25510).

21. 8 bit internal bus Instruction Reg. Instruction Decoder and Machine Cycle Encoding Timing and Control X1 X2 Instruction register and decoder  It is an 8-bit register.  When an instruction is fetched from memory then it is stored in the Instruction register.  Instruction decoder decodes the information present in the Instruction register. Timing and control unit  It provides timing and control signals to the microprocessor to perform operations.  Following are the timing and control signals, which control external and internal circuits − 1.Control Signals: READY, RD’, WR’, ALE 2.Status Signals: S0, S1, IO/M’ 3.DMA Signals: HOLD, HLDA 4.RESET Signals: RESET IN, RESET OUT