Chapter 2: MCU Archi and Embed C

Von Neumann Architecture
1. Stored program computer
2. Stores program data and instructions data in the same memory (RAM)
3. CPU / Processor: Central Processing Unit
4. Memory: Stores data and program
5. I/O / Peripherals: For CPU to interface to external world.
6. Address bus: Determine which location
7. Data Bus: Determine the data size
8. Control Bus: Determine the type of instruction (read / write)
I/O and Interfacing with Externals
1. Connection
  1. Loosely Coupled: For external interface
    1. via external bus
    2. via network
    3. via port
  2. Tightly Coupled: For internal interface
    1. via fast internal bus
2. Data Transfer
  1. Serial
    1. Transmit data bit by bit
    2. Requires at least 2 wires to support bidirectional communcation
    3. Low speed but is the standard for external interface
  2. Parallel
    1. Transmit data multiple bits at a time
    2. Require multiple interconnections and additional synchronization mechanism
    3. Fast but limited to short distance, mostly used for internal interfacing
3. OS
  1. Multitasking: Perform more than one task
  2. Multithreading: Different parts of same program executed simultaneously
  3. Multiprocessing: Work appears to be simultaneous because of speed of proceesor
  4. CPU Speed: Measure of number of instructions CPU can carry out per second
    1. 2.5GHz CPU: 2.5 billion cycles / second
Microcontroller Selection
1. Key Selection Criteria
  1. CPU computation requirements
  2. Number of I/O available
  3. Support in terms of tools and software libraries availability
  4. Cost
  5. MCU Manufacturer
  6. Power Consumption
2. Memory Options
  1. Types: Masked, EEPROM, Flash, RAM, FRAM
  2. Size: Can have a wide range
3. Internal Peripherals
MSP430
1. CPU Block Diagram
  1. PC: Address of next instruction to be executed
  2. SP (20 bit): Points to RAM reserve to store program context so that it can return after subroutine / interrupt processing.
  3. SR: Contains a set of flags (C, Z, N, V), GIE and MCU mode selection bits
  4. Constant Generator: 6 most frequently used values
  5. General purpose registers: 12
2. Key Features
  1. Ultra Low Power
  2. Increased Performance
  3. Innovative Features
  4. 16-bit RISC computer based on Von Neumann architecture
3. Memory: Sequential list of addressable storage elements
  1. Program / Instruction: A sequence of instructions
  2. Not possible to differentiate instruction and data
  3. Data: Values instructions operate on
Embedded C
1. Identifiers
  1. const: Constant; stored in program section memory
  2. extern: To make reference to variables declared elsewhere
  3. static: Preserves the variable even after function/block
  4. volatile: To allow changes of variable by an event outside program i.e. ADC
2. Directives
  1. include: to include a file as part of source code
  2. define: substitute a name by corresponding expression
  3. pragma: compiler specific directive; instructs compiler to use implementation dependent features

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Chapter 2: MCU Archi and Embed C

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