Department of Computer Engineering University of Kashan Department of Computer Engineering MicroProcessors & MicroControlers H. Sabaghian B. Spring 2006

Text Books Microcontroller 8051 Author: Mohammad ali Mazidi Translator: Dr. Sepidnam The 8051 Microcontroller Author: Iscott Makenzi Translator: Dr. Seyed Razi Edition : 3

Introduction Lec note 1

outline Microprocessor Micro-computer Microcontroller 3_Bus (Data, Address, Control) I/O Memory

Microprocessor (µP)(MPU) µP = CPU on a single chip Components of CPU Registers: Temporary storage locations for program instruction or data. The Arithmetic Logic unit (ALU): performs both arithmetic and logical operations Timing and Control Circuits: keeps all working together in the right time sequence Bus: n_bit (internal) path for data exchange

Microprocessor Microprocessor=µP=MPU Tasks processing data controlling all components make µP the µComputer system µP executes instructions in memory Fetch, Decode, Execute

Microcomputers Micro-computer (µ-Computer) small computer specifically for data acquisition and control applications

Microcomputers All Microcomputers consist of (at least) : Microprocessor Unit (µP) Program Memory (ROM) Data Memory (RAM) Input / Output ports (IO) Bus System (External) (and Software) MPU is the brain of microcomputer

The Input/Output (I/O) System I/O links MPU to outside world. Input port : a circuit through which an external device can send signals (data?) to the MPU. Output port is a circuit that allows the MPU to send signals (data?) to external devices. I/O ports connect both digital and analogue devices by DAC and ADC

Bus A common communications pathway that carry information between the various elements of system The term BUS refers to a group of wires or conduction tracks on a printed circuit board (PCB) though which binary information is transferred Subsystems are connected through BUS together

3_Bus There are three main bus grouPs ADDRESS BUS DATA BUS CONTROL BUS

Data Bus The Data Bus carries the data which is transferred throughout the system. ( bi-directional) Examples of data transfers Program instructions being read from memory into MPU. Data being sent from MPU to I/O port Data being read from I/O port going to MPU Results from MPU sent to Memory These are called read and write operations

Address Bus Address = binary number that identifies a specific memory storage location or I/O port involved in a data transfer Address Bus = pathway transmit address to memory or I/O port. Address Bus is unidirectional (one way): addresses are always issued by the MPU

Control Bus Control Bus = grouP of control signals Control signals are unidirectional, and are mainly outputs from the MPU. provide synchronization (timing control) between MPU and other components. Example RD: (read signal) read data into MPU WR: (write signal) write data from MPU

Main memory Memory Main memory Types Stores programs Provides data to the MPU Accepts result from the MPU for storage Main memory Types ROM : read only memory. Contains program (Firmware). does not lose its contents when power is removed (Non-volatile) RAM: random access memory (read/write memory) used as variable data, loses contents when power is removed volatile. When power up will contain random data values

Read-Only Memory µP can read instructions from ROM quickly Cannot write new data to the ROM ROM remembers the data, even after power cycled When power is turned on, the microprocessor will start fetching instructions from ROM (bootstrap ) On a PC, the ROM is called the BIOS (Basic Input/Output System). When the microprocessor starts, it begins executing instructions it finds in the BIOS. The BIOS instructions do things like test the hardware in the machine, and then it goes to the hard disk to fetch the boot sector. This boot sector is another small program, and the BIOS stores it in RAM after reading it off the disk. The microprocessor then begins executing the boot sector's instructions from RAM. The boot sector program will tell the microprocessor to fetch something else from the hard disk into RAM, which the microprocessor then executes, and so on. This is how the microprocessor loads and executes the entire operating system

Available ROMs Masked ROM or just ROM PROM or programmable ROM(once only) EPROM (erasable via ultraviolet light) =UVROM Flash re-writable about 10000 times usually must write a whole block not just 1 or 2 bytes, slow writing fast reading EEPROM (electrically erasable ROM) fast writing slow reading can program millions of times useless for storing a program good for save configuration information.

ROM ROM Capacity : PROM EEPROM : Output Enable connect to RD of µP m+1 bit Address n+1 bit Data Am Dn ROM PROM EEPROM Capacity : : Output Enable connect to RD of µP : Chip Enable to Address decoder

Addr valid to data valid ROM Read Timing A0-Am D0-Dn OE falls to data valid Addr valid to data valid

27XX EPROM PGM and VPP are used to programming 64 kbit 8 kbyte 16 kbit

27XXX EPROM 128 kbit 16 kbyte 256 kbit 32 kbyte 512 kbit 64 kbyte

28XX E2PROM 16 kbit 64 kbit 1026 kbit 4096 kbit 256 kbit 2 kbyte

RAM (Random Access Memory) µP can read the data from RAM quickly µP can write new data to RAM quickly RAM forgets its data if power is turned off Two type is available : Static RAM(SRAM): ff base, fast, expensive, low cap/vol, applied for cache , no refresh Dynamic RAM (DRAM): cap base, slow , low cost high capacity/volume , applied for main memory(pc) need refresh. RAM stands for random-access memory. RAM contains bytes of information, and the microprocessor can read or write to those bytes depending on whether the RD or WR line is signaled. One problem with today's RAM chips is that they forget everything once the power goes off. That is why the computer needs ROM

RAM(Static) Capacity : RAM Data bus is Bidirectional : Read signal m+1 bit Address n+1 bit Data Am Dn Capacity : RAM Data bus is Bidirectional : Read signal connect to MemRD of µP : Write signal connect to MemWR of µP : Chip Select to Address decoder

Static RAM

Dynamic RAM

Dynamic RAM Write : Charge bitline HIGH or LOW and set wordline HIGH Read : Bit line is precharged to a voltage halfway between HIGH and LOW and then the word line is set HIGH. Sense Amp Detects change Reads are destructive (Must follow with a write) Address Buffer