Basic concepts Microchip PIC 8-bit PICs 16-bit PICs 32-bit PICs Final stuff
Microcontrollers
Z. Matej & S. Rerucha
Spring 2013
Basic concepts Microchip PIC 8-bit PICs 16-bit PICs 32-bit PICs Final stuff
1 Basic concepts
2 Microchip PIC
3 8-bit PICs
4 16-bit PICs
5 32-bit PICs
Basic concepts Microchip PIC 8-bit PICs 16-bit PICs 32-bit PICs Final stuff
Microcontroller
...also referred to as: MCU, uC, µC.
MCU is basically a “computer-on-a-chip”: microprocessor,
data and program memory, I/O peripherals; usually also
interrupt controller, timers, non-volatile storage (EEPROM)
Various extra peripherals usually integrated : analog
peripherals (A/D, D/A, comparators), serial communication
(UART, SPI, IIC), drivers (LCD, PWM)
Typically used for low-cost, space- and power-critical
applications
Simple architecture also allows for better real-time capabilities.
Special branch of MCUs targeted at signal processing is recognized
as the Digital Signal Controllers, DSCs.
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Scale
Data memory: from 16B to several MB
Program memory: from 250 words to several MB
Clock speed: typically a few MHz (1-20), 32kHz for ultra low
power, 500+ for hi-end cores
I/O size: from 6 pins (incl. power)
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µC vs. microprocessor
all components on a single
chip
fixed memory and I/O size
for cost / power / space
-critical applications
reduced complexity ⇒
reliability, real-time response
only processing unit, the rest
connected externally
modularity: arbitrary I/O
and memory
performance
versatile, expandable
Nowadays both can be either general purpose or application
specific.
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MCU Taxonomy
architecture: Von Neumann, (Modified) Harvard
instruction set: RISC, CISC, ...
addres bus width: 8-, 16-, 32-, 64-bit
platform: IC, soft-core
family: acording to manufacturer (see [1])
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Harvard vs. von Neumann
In Von Neumann architecture, the data and program memory are
stored in a single memory ⇒ more universal concept
In Harvard architecture, there are separate memories and buses for
data and program memory ⇒ simultaneous access to instructions
and data, different bus widths.
Basic concepts Microchip PIC 8-bit PICs 16-bit PICs 32-bit PICs Final stuff
Basic models developed
Modified Harvard architecture: the architecture allows for
modification of the program memory from the system itself, e.g by
special instructions
Memory mapped I/O: the peripheral interfaces are mapped into
single continguous memory space.
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Instruction sets
Complete Instruction Set Computer (CISC): large instruction
set performing even complex tasks; usually takes several clock
cycles to execute – e.g. Intel 80x86, Zilog Z80, 8051
Reduced Instruction Set Computer (RISC): small instruction
set, fast and fixed time execution (good for pipelining); complex
task are done as a combination of more instructions – e.g. ARM,
Sparc, Atmel AVR MIPS, PowerPc, PIC
Today, an amorphous combination is typically used, the only CISC
computers are x86s.
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Introducing PICs
PIC ... Peripheral Interface Controller or Programable Intelligent
Controller by Microchip company
Popular for wide range of devices with uniform design concepts,
low cost devices, free or low cost development tools, serially
reprogrammable instruction memory, large user base, extensive
collection of application notes and support materials.
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PIC families
8-bit controllers: PIC10, PIC12, PIC16, PIC18
16-bit general purpose: PIC24F, PIC24H/E
16-bit digital signal controllers: dsPIC30, dsPIC33
32-bit controllers: PIC32
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General properties
Modified Harvard architecture – separate code and data space
RISC – small amount of fixed-length instructions
single cycle instruction execution (1-4 clock cycles)
small adressable data space, extended through banking
memory-mapped registers & peripherals (all in single address
space)
low power consumption: scalable oscillators, power-down
modes, peripherals disabling
hardware stack (8-bits)
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Typical features
General purpose I/O pins
Internal clock oscillators
8/16/32-bit timers
Watchdog timer with separate clock oscillator.
Internal non-volatile memory (EEPROM)
ICSP – in-circuit serial programming
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Typical features II.
Synchronous/Asynchronous Serial Interface USART.
MSSP Peripheral for I2C and SPI Communications.
Capture/Compare and PWM modules
Analog peripherals: A/D converters (up to 1.0 MHz), DAC,
comparator, voltage references
USB, Ethernet, CAN interfacing support.
External memory interface.
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8-bit Core Architectures
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8-bit Families
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8-bit Baseline architecture
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8-bit Mid-range architecture
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8-bit Enhanced mid-range architecture
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8-bit PIC18 architecture
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16-bit Families
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16-bit PIC24F architecture
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16-bit PIC24E/H architecture
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16-bit dsPIC30 architecture
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16-bit dsPIC33 architecture
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32-bit Family
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References
[1] List of common microcontrollers
http://en.wikipedia.org/wiki/List_of_common_microcontrollers
[2] Microchip company website
http://www.microchip.com