Introduction to Microcontroller

Introduction to Microcontroller

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  Introduction to Microcontroller www.pantechsolutions.net 1
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  What is Microcontroller? • In simple term – Microcontroller is a small computer that is capable of performing specific task(s) – e.g car alarm, washing machine, handphone, PDA… • There are many similar names – Microprocessor-based system, controller, MCU, MPU, CPU… • They can be grouped into two classification  MCU - Micro Controller Unit  MPU - Micro Processor Unit • In general, these microcontroller are the brain of the embedded system 2
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  MCU and MPU Classification MCU MPU Chip Embedded A CPU core, memory, Contain only the main processor (CPU peripherals, IO … into a single chip. core) Block Diagram of a MCU system Memory Memory IO CPU Core Peripheral MPU Peripheral IO General Application - Self contained to complete a task. -Need external memory, peripheral to Area - Targeted for small, compact, and accomplish a task low cost system - Targeted for complex, high performance and expandable system Processor (CPU) Core 4, 8, 16 bit 32 bit or above Examples 8051,pic16f887a,M16, H8, SH1/2 SH3/4,8085 Application Washing machine, car side mirror, Handphone, PDA air con 3
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  Components within MCU Clock -sub Processor Core i. Processor core Clock -main RAM ii. Clock ROM PWM iii. Low power mode iv. Memory(ROM/RAM) Timer PWM v. Input/Output Port Timer Timer vi. Timer / Counter/ WDT Serial vii. PWM Timer Port Interface viii. ADC/DAC Timer WDT ix. Serial Interface ADC LCD x. On chip Debug xi. Bus Controller Example of H8/38024 xii. Other 4
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  i. Processor core • Function – Fetch and execute machine code from memory – Efficiency & Effectiveness are determine by its architecture • Architecture Type – Word Size: 4, 8, 16, 32 Bit – Contains ALU (Arithmetic Logic Unit) for decision process – Contains General Registers for temporary storage and data manipulation – Contains Special Registers (PC, Condition, Stack) to assist in program control – Instruction Sets – RISC /CISC – Running Frequency / Voltage • Possible Measurement – MIPS (Million Instruction Per Instruction) • Number of machine instructions that a computer can execute in one second • Provide only a rough indication for comparison 5
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  ii. Clock OSC1 OSC2 • MCU needs a clock input to operate • It can have two clock sources – A. Main processor clock input • This clock may be divided or multiply to allow the processor to run at a slower speed (lower power consumption) or higher speed – B. Sub clock input • 32.768KHz is the usual clock used as this allow accurate generation of a second via a 16 bit counter. • These clocks are normally fed via a crystal and two capacitors to the MCU. 6
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  iii. Low powermode • Low Power is achieved via various mean – Running at slower speed, such as sub clock(32.768KHz) • Sleep mode, sub-active, standby… – Shutting off unused peripherals • Module stop mode… Standby mode consume only 1uA 7
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  iv. Memory (ROM/RAM) • ROM (Read Only Memory) – For program and fixed data storage – Size: as low as 1 KByte to as high as 512 KByte – Example 1. Masked ROM 2. Flash 3. PROM - Programmable Read-Only Memory 1. OTP - One-Time Programmable • RAM (Random Access Memory) – For data storage – Size: as low as 256 Byte to as high as 4 KByte – Example 1. SRAM 8
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  v. Input /Output Port • Basic interface to control (output) and monitor (Input) external events. – High current port • (20mA), so as to drive LED directly. – Open-collector/drain port • Interface to higher supply circuitry • Wired-Nor condition 9
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  vi. Timer /Counter / WDT • Timer (8 or 16 bit) are used to generate or measure timing for events. – External event trigger the count – Compare match to perform a task – … • WDT (WatchDog Timer) – Every time before the counter reach the predefined value, the working MCU will clear the counter. – Thus, if the counter is not clear within the specified timing, the WDT will reset the whole MCU as this signify that the MCU has run wild. 10
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  vii. PWM • PWM(Pulse Width Modulation) – Generate continue pulse of preset duty cycle • This can be used to drive motor. 11
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  viii. ADC/DAC • ADC(Analog-to-Digital Conversion) – The basic peripheral to interface to the real analog world. – Characteristic • Accuracy is determine by number of bits (10,12,14…) • Sampling frequency • Conversion technology ( Resistive ladder, Sigma delta…) Analog Digital – AVCC, Data -> and eachTransducer input pins AVSS Real World analog ADC CPU Temperature Pressure Sound… • DAC (Digital-to-Analog Conversion) – This operate in another way. It output the signal in analog form to the outside world 12
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  ix. Serial Interface •There are different serial interfaces – Asynchronous mode (2400 BaudRate…) – Synchronous mode (at higher transfer rate) – USB, I2C, SPI, CAN…(different communication standard) • Use for: – Communication with other devices, such as external RF module, PC… • Generally used only 3 pins – Serial In, Serial Out, and Clock 13
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  x. On ChipDebug • Circuitry Incorporated for development and debugging purposes • Usually few pins are required for the PC to control the MCU, via a “JTAG-like” emulator – Mode pin – Data In/Out – Clock pin PC USB I/F Target Board 14
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  xi. Bus Controller •In the higher performance MCU, a bus controller is incorporated to manage internal and external memory bus. • The external bus may be split into different areas, so that each area can be assigned with different setting – Refresh controller for DRAM – Longer wait cycles for slower devices 15
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  xii. Other • Thereare many possible peripherals that can be integrated into each MCU, to perform specific tasks, such as: – LCD controller – PLC – Ethernet MAC • Other components are: – Interrupts – LVD (Low Voltage Detection) – POR (Power On Reset) 16
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  MCU Connection Flashing Supply via battery or wall plug /Debugging (Optional) VCC Clock Output Control Motor, LED, Mode MCU Reset Input Monitor Temperature, Switches… GND 17
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  Choosing MCU 1. Reliability - good 2. Performance – speed, number of bits, architectures 3. Power consumption - low 4. Peripherals – require 5. Number of I/O pins - enough 6. ROM/RAM size – enough 7. Package and Size – manufacturing ease 8. Development Tool – available and ease of Use 9. Roadmap – for next expansion 10. Cost - low 11. Availability – short lead time 12. Support – technical team, application notes… 18
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