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Introduction to Microprocessor’s & Microcontroller

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1 Introduction to Microprocessor’s & Microcontroller
Prepared by Md. Zakir Hossain Lecturer Dept. of EEE, KUET

2 Contents 8085 Microprocessor Bus, CPU, Memory and I/O of 8085 μp
The 8085 Bus Structure CPU Internal Structure Hardware Description of uPC-MICRO 8085 Keys and Key Functions 8086μp internal architecture Function of Keypad & Register ATmega8(L) microcontroller

3 Microprocessor A microprocessor is a multipurpose, programmable, clock-driven, register based electronic device that reads binary instructions from a storage device called memory; accepts binary data as input and processes data according to those instructions, provides results as output. Fig1. CPU internal structure of 8085 microprocessor

4 The 8085 Bus Structure Address Bus
The internal architecture of the 8085 CPU is capable of performing the following operations: Store 8-bit data (Registers, Accumulator) Perform arithmetic and logic operations (ALU) Test for conditions (IF / THEN) Sequence the execution of instructions Store temporary data in RAM during execution the ALU includes a temporary register used for holding data temporarily during the execution of the operation. This temporary register is not accessible by the programmer. The 8085 Bus Structure The 8-bit 8085 CPU (or MPU – Micro Processing Unit) communicates with the other units using a 16-bit address bus, an 8-bit data bus and a control bus. Address Bus The address bus has 8 signal lines A8 – A15 which are unidirectional. The other 8 address bits are multiplexed (time shared) with the 8 data bits. 16 address lines are capable of addressing a total of 216 = 65,536 (64k) memory locations. Address locations: 0000 (hex) – FFFF (hex) Identify perifheral or memory locations

5 The 8085 Bus Structure Data Bus Consists of 8 data lines: D0 – D7
Fig2. The 8085 Bus structure Data Bus Consists of 8 data lines: D0 – D7 Operates in bidirectional mode Data range: 00 (hex) – FF (hex) use for transferring data Control Bus Consists of various lines carrying the control signals such as read / write enable, flag bits.

6 The 8085 programmable registers
Six general purpose 8-bit registers: B, C, D, E, H, L They can also be combined as register pairs to perform 16-bit operations: BC, DE, HL Registers are programmable (data load, move, etc.) Accumulator Single 8-bit register that is part of the ALU . Used for arithmetic / logic operations – the result is always stored in the accumulator. Fig3. The 8085 programmable registers

7 The Program Counter (PC)
is used to control the sequencing of the execution of instructions. always holds the address of the next instruction. since it holds an address, it must be 16 bits wide. The Stack pointer is also a 16-bit register that is used to point into memory. this register points to in a special area called the stack. the stack is an area of memory used to hold data that will be retreived soon. the stack is usually accessed in a Last In First Out (LIFO) fashion. Memory: Where instructions (programs) and data are stored Organized in arrays of locations (addresses), each storing one byte (8 bits) in general A read operation to a particular location always returns the last value stored in that location I/O devices: Enable system to interact with the world Device interface I/O registers are connected to external wires, device control logic, etc. Reads may not return last value written Writes may have side effects

8 Indicate the result of condition tests.
The Flags register Flag Bits Indicate the result of condition tests. Carry, Zero, Sign, Parity, etc. Conditional operations (IF / THEN) are executed based on the condition of these flag bits. There is also the flags register whose bits are affected by the arithmetic & logic operations. S-sign flag The sign flag is set if bit D7 of the accumulator is set after an arithmetic or logic operation. Z-zero flag Set if the result of the ALU operation is 0. Otherwise is reset. This flag is affected by operations on the accumulator as well as other registers. (DCR B). AC-Auxiliary Carry This flag is set when a carry is generated from bit D3 and passed to D4 . P-Parity flag After an ALU operation if the result has an even # of 1’s the p-flag is set. Otherwise it is cleared. So, the flag can be used to indicate even parity. CY-carry flag After an operation, if the result in the accumulator is larger than 8 bits, the flip-flop that is used to indicate a carry, called the carry flag. S Z AC P CY

9 8085 Instruction Set Between registers Data transfer operations
Between memory location and a register Direct write to a register / memory Between I/O device and accumulator Arithmetic operations (ADD, SUB, INR, DCR) Logic operations Branching operations (JMP, CALL, RET)


11 Hardware Description uPC-MICRO 8085 system consists
crystal controlled oscillator buffers for address data control signals two 8255 (Programmable Peripheral Interface) one 8279 (Programmable keyboard & display controller) one 8253 (Programmable interval timer) one 8259A (Programmable Interrupt Controller) One 8251A (Programmable Communication Interface) with RS232C drivers & receivers. 8 digit seven segment display 32 keys with one RESET key in keyboard

12 Base port address in Hex
Memory decoding & addresses System EPROM : 0000 to 0FFF (32K) RAM (CMOS) : 8000 to 9FFF (8K) (8000 to 97FF user RAM) (9800 to 9FFF system RAM) Expansion RAM : A000 to BFFF (8K) C000 to DFFF (8K) I/O decoding and addresses SL. No. Peripheral LSI Base port address in Hex 01. A8255 00 02. B8255 20 03. 8251A 10 04. 8253 30 05. 8257 08 06. 8259A 28

13 Display interface Keyboard interface Serial interface
Once a data is written to 8279 display RAM, 8279 automatically refreshes the data on 8 digit 7 segment LED display. One can optionally connect a LCD module to the port lines of the connector provided and writing the necessary software. Keyboard interface 16 keys are assigned for 16 hexadecimals 16 keys for executing different functions 1 key mounted on the motherboard Serial interface duplex serial communication interface use 8251A serial communication controller with RS232C drivers at its output & RS232C receivers at its input Software description At power on or at manual RESET, the CPU starts execution. Before executing the main routine, the various peripherals, flags and parameters in RAM are initialized.


15 Executing a program in uPC-MICRO 8085
Label Mnemonics Op-code Operand Hex Code Memory address START MVI A, ECH 3E, EC MVI B, F1H 06, F1 MVI C, 00H 0E, 00 ADD B 80 8006 JNC LOOP1 D2, 0B, 80 INR C 0C 800A LOOP1 STA 32, 90, 80 800B-0D MOV A, C STA 79 32, 91, 80 800E 800F-11 END HLT 76 8012

16 The 8085 and 8086 Microprocessors
Fig4. Pin layout of the 8085 and 8086 microprocessor

17 Features of 8086 μp Execution Unit (EU) FLAG Register
CPU is divided into BIU & EU Execution Unit (EU) tells the BIU where to fetch instructions or data from, decodes instructions and executes instructions Has a 16 bit arithmetic logic unit Decode instructions and done internal operations FLAG Register 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 / O D I T S Z A P C Control Flags Trap flag (TF) >> used for single stepping through a program Interrupt flag (IF) >> used to allow or prohibit the interruption of a program Direction flag (DF) >> used with string instructions Conditional Flags Carry Flag (CF), Parity Flag (PF), Auxiliary Carry Flag (AF), Sign Flag (SF) ,Zero Flag (ZF) & Overflow Flag (OF) >> will be set if the result of a signed operation is too large

18 8086μpU internal architecture
General register a. Data register (AX (AL & AH), BX (BL & BH), CX (CL & CH), DX (DL & DH)) used to store data b. Pointer & Index register (16 bit) Stack Pointer (SP) >> holds the 16 bit offset from the start of segment Base Pointer (BP) >> holds the 16 bit offset and used for temporary store of data Source Index (SI) >> holds the 16 bit offset of data word in the data segment Destination Index (DI) >> used to indirect addressing & operation and temporary store of data Fig5. General purpose registers

19 Instruction Pointer (IP)
Bus Interface Unit (BIU) handles all transfers of data & addresses on the buses for the execution unit The Queue stores prefetched bytes in first-in-first out fashion for EU Fetching the next instructions when the current instruction executes is called pipelining Extra Segment (ES) Code Segment (CS) Stack Segment (SS) Data Segment (DS) Instruction Pointer (IP) Fig6. Segment registers used to hold the upper 16 bits of the starting addresses of four memory segments Segment address (3000H) H Offset address (1234H) H Real address H

20 Introduction to the MTS-86C microprocessor
CPU or “brain” ROM has addresses F0000H through FFFFFH and non-volatile RAM has addresses 00000H through 10000H and volatile Keyboard/display interface ( an 8279 device) 24 Key Keyboard Display: LCD Expansion area (upper left-hand side) Prototyping area (left-hand side) Reset Volatile memory 16 of data line and 20 of address line

21 Function of Keypad Memory

22 I/O Port address assignments
Port function FFFFH FFFDH FFFBH FFF9H PPI-1 control word resister PPI-1 C port PPI-1 B port PPI-1 A port Parallel I/O No. 1 FFFEH FFFCH FFFAH FFF8H Parallel I/O No. 2 FFF2H FFF0H command data RS232C PORT 1 FFE8H 8279 Status or Command 8279 Data Keypad control FFDEH FFDCHFFDAH FFD8H 8253 Command 8253 Count 2 8253 Count 1 8253 Count 0 Counter & Timer FFD2H FFD0H Command data RS232C PORT 2 Port address Port function FFCAH FFC8H 8259 Command 8259 Data Interrupt control 3FF0H FND Display 3FD8H D/A Converter 8 bit D/A converter 3FD6H 3FD4H 3FD2H 3FD0H PPI-1 control word resister PPI-1 C port PPI-1 B port PPI-1 A port Experiment for 8 bit output and input 3FCEH 3FCCH 3FCAH 3FC8H A/D Converter IN3/IN7 A/D Converter IN2/IN6 A/D Converter IN1/IN5 A/D Converter IN0/IN4 8 bit A/D Converter

23 Example : *Knowing that, DS=2042H. SI=500H, AX=214E, MOV [SI],AX ; AH
AL 21 4E 21 20921H 4E 20920H SI=500 DS=20420H DS=2042H

24 24 Executing a program in MTS-86C Label Mnemonic Hex code
Memory address Remarks CODE SEGMENT 0040: ASSUME CS: CODE & DS: CODE Result will be MOV AX, 1234H B8, 34, 12 00, 01, 02 stored in AX MOV CX, 0034H B9, 34, 00 03, 04, 05 ADD CX 03, C1 06, 07 HLT F4 08 ENDS END 24

25 History of microprocessor
8008 8080 8085 8086 Number of instructions 66 111 113 133 Number of flags 4 5 9 Maximum memory size 16K bytes 64K bytes 1 M bytes I/O ports 8 input 24 output 256 input 256 output 64K input 64K output Number of pins 18 40 Address bus width 8 16 20 Data bus width Introduction date 1972 1974 1976 Q-6,500 at 3 µm 1978 Q-29,000 at 3 µm

26 What Are Microcontrollers?
Microprocessor – Microcontroller what's the diff? Microprocessors can not stand alone instruction decoder, ALU, address/data. busses, timing logic, (CPU) Has no capability to interact with the outside world memory, I/O ports, UARTS, etc. must be added to make it useful Microcontrollers are small computing systems on a single chip Central Processing Unit (CPU) Program memory Random Access Memory (RAM) EEPROM - Electrically Erasable Programmable Read Only Memory A variety of peripheral devices USARTs, Timer/Counters, ADC, DAC, I/O Ports, CANs, SPIs etc.

27 Why not a Computer ? Why MCU
• Suppose we want to make a Line following Robot • What do we do ? • Use a computer with 2.4Ghz Intel core I7 with 4 Gb RAM , 500 Gb Hard disk , 1 Gb Graphics Card ?? Why not a Computer ? • PC is a general purpose computer. • Can run thousand of software's • Games (NFS , AOE , Call of Duty) • Highly expensive Why MCU • Small reflected by the word “MICRO” • Inexpensive • Ideal for doing repetitive tasks • Easy to use • Highly Efficient and fast

28 ATmega8(L) microcontroller
The Atmel ®AVR® ATmega8 is a low-power CMOS 8-bit microcontroller based on the AVR RISC architecture. By executing powerful instructions in a single clock cycle, the ATmega8 achieves throughputs approaching 1MIPS per MHz, allowing the system designer to optimize power consumption versus processing speed. Fig7. Pin configuration of ATmega8(L)

29 Conclusion Finally, you should write a report with clear conception for different contents described above. References Microprocessor Architecture, Programming and Applications with the 8085/8080A by Ramesh S. Gaonkar Microprocessors and Interfacing by Douglas V Hall and Internet

30 Thanks to all ??

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