MICROCONTROLLERS

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MICROCONTROLLERS
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What is a microcontroller?

• A microcontroller is a nifty little gadget that
  houses a microprocessor, ROM (Read Only Memory),
  RAM (Random Access Memory), I/O (Input Output
  functions), and various other specialized
  circuits all in one package.

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Zilog Z-80
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What is the Z-80 family of components?

• significant advancement in the state-of-the-art
  of microcomputers. It can be configured with any
  type of standard semiconductor memory to generate
  computer systems with an extremely wide range of
  capabilities. With additional memory and I/O
  devices a computer can be constructed with
  capabilities that only a minicomputer could
  previously deliver.
• Advantages
• fully software compatible with the popular 8080A
  CPU
• superior in both software and hardware
  capabilities (less cost and more features)
• offers the user significant speed advantages (up
  to 16 MHz clock rate)
• including full software support

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Z-80 CPU

• Z80 microprocessor is an 8 bit CPU with a 16 bit
  address bus capable of direct access of 64k of
  memory space. It has a language of 252 root
  instructions and with the reserved 4 bytes as
  prefixes, accesses an additional 308
  instructions. The Z80 was modeled after the 8080
  and contains the 78 - 8080 opcodes as a subset to
  it's language.

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• Programming features include an accumulator and
  six eight bit registers that can be paired as
  3-16 bit registers. In addition to the general
  registers, a stack-pointer, program-counter, and
  two index (memory pointers) registers are
  provided. While not in the same league as the
  80486 or 68000 series, the Z80 is extremely
  useful for low cost control applications. One of
  the more useful features of the Z80 is the
  built-in refresh circuitry for ease of design
  with DRAMs.

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• It comes in a 40 pin DIP package. And recently
  also in a 44 pin SMD and QFP. It has been
  manufactured in A, B, and C models, differing
  only in maximum clock speed. It also has been
  manufactured as a stand-alone microcontroller
  with various configurations of on-chip RAM and
  EPROM.

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Peripheral Interface Controller (PIC)
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What is a PIC?

• PIC stands for Peripheral Interface Controller,
  which is Microchip, Inc.'s trademark for their
  line of 8-16 bit microcontrollers. Actually,
  Microchip's official name for the lineup is
  PICMicro.

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More about PICs

• Various models are available with different
  peripherals built in such as multiple timers,
  A/D conversion, serial interfacing, LCD control,
  etc. They are also available in SMT packaging or
  standard DIP packaging with as many as 68 pins or
  as few as 8 pins. Some of the latest versions
  (and many future versions) have flash memory,
  making for simple erasures and reuse. Most of the
  current versions employ EPROM which requires
  erasure with a special UV lamp.

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• If you want to develop firmware for a PIC, you
  will need an erasable version. The erasable types
  available are of the EPROM, EEPROM, and flash
  memory varieties. EEPROM and flash memory devices
  are great because they don't need that UV eraser
  and are less expensive. Unfortunately the flash
  and EEPROM (EEPROM is being phased out in favor
  of flash) versions are not available in all
  configurations, but it seems Microchip is
  expanding their horizons. One of the most popular
  versions of the PIC for beginners is the
  PIC16F84. It uses flash memory (hence the F in
  its part number), and has 18 pins. Thirteen of
  these pins can be used for input or output
  purposes.

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What can one use a PIC for?

• PICs are very versatile and can be used in
  practical projects such as burglar alarms, caller
  ID boxes, remote controls, clocks, and just about
  anything you can think of that could use a single
  chip self contained computer.

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Why choose PICs?

• Because getting into them wasn't a big investment
  They have a lot of bang for the buck. There are
  only about 35 simple RISC-type (Reduced
  Instruction Set Computer) commands to learn.
  There is a lot of help available for beginners.

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Developing the PIC

• First choose the PIC.
• Learn a language.
• Choose the programmer.
• Wire the circuit on the target board.
• Write the code.
• Program.

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Sample Program Blinking Lights

• list p16f84
• porta equ 0x05
• portb equ 0x06
• org 0x000
• start movlw 0x00
• tris porta
• movlw 0x00
• tris portb
• clrf porta
• clrf portb
• hi bsf porta, 0
• bcf porta, 0
• goto hi
• end

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