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Microcontrollers Introduction

Submitted by garthee on Sun, 2008-07-20 18:13.

Microcontrollers is a hot-topic thesedays with the introduction of wireless support - let it be bluetooth, zigbee or wifi - that is being added inbuilt. To kindle some interest and assist in answering questions that could be asked in any introduction level courses the digest from techonline course on microcontrollers.

System on chip
Same functionalities as of a computer in a chip
Always contains
- CPU (ALU, Instruction decoder, register, counter, stack pointer)
- Memory (RAM, ROM)
- I/O (Serial, I2C)
- Peripheral (Timer, counter, ADC, PWM)
Comparison
- Microprocessor - External memory , peripheral, external address / data busses
- Microcontroller - all inside but specially for controlling
- DSP - mathematical calculations
History
- MU: TMS1000 (first)
- MP: Intel 4004 - 8008,8080-pc, Motorola 6800 (later MU 68000 as well) - mac
Bit definition - 8bit means data bus width, rarely related to address bus
CISC - hardware is faster than software - powerful instruction , shorter code - complex circuit to decode
RISC - more instructions will be needed, and compilers must generate complex instructions that were available readily in CISC

Harvard - separate bus for data and program
- Both data / instruction can be fetched
- Complex memory management
Princeton / Von Neumann - the same bus
Complex interlaced instructions / data fetching
Interrupts
- Can be external or internal (CPU generated)
- Programmable Interrupts (PI) / Advanced PI (API)
- Latency - Time to act on - critical for RTOS
ROM - Program memory , non volatile - Masked ROM, PROM, EPROM, OTP, EEPROM, Flash
RAM - nonvolatile, SRAM (faster, common in MU), DRAM(slower)
I/O serial - USB
- CAN(automobile, automation)
- SPI (4wires, motorola)
- I2C(2wires, philips)
- UART (RS232)
- LIN (Local Interconnect Network), ETHERNET
- Wireless - ZigBee, Bluetooth
On chip peripherals
- Timer - counter, watchdog timer
- LCD controller
- GPIO - do not have any specific actions - just register settings - tri state
Low power
- Dynamic power - application based
- Static power - standby power - turning off various components
- Lower power modes - Deeper the sleeping state, greater the time needed to wakeup
Licensed Cores
- 8051 - From Intel - now NXP , Atmel
- Arm - ARM 5 , 9 , 11
- MIPS - Microchip
Vendors
- Renesas - (Hitachi - Mitsubishi) - world leading - mainly RISC
- ATMEL - popular for AVR architecture
- Freescale - (Motorola) - MC68K
Development tools - Editor, Compiler, Assembler, Linker, (Simulator, Debugger)
- IDE
- In circuit emulator - allow viewing control / control of program as seen within the chip
- JTAG - interface for test and debug - obliterating In CE
- Evaluation kits - MCU test drives and quick evaluation
- 3rd party tools
Designing of a system
- Product specification - market analyse / drivers
- Real world interfaces - sensors , display
- MCU needed to meet functions
- MCU that suits
- Smaller design - hardware , Bigger design - software tool
- Features - DAC, PWM | Communication Interface | Package - size, pins
- Power - sleep modes, voltage | Speed - clock F, Interrupt latency, Critical inst
- Reliability - demands, environment, temperature, Memory - size, type
Choosing a MU
- Familiarity
- Price - device, volume, software, OS, compiler
- Available kits - evaluation, development, reference design
- Documents - white papers, example code, user guide, Community
- Portability / Scalability - roadmap, large family, abstraction layer