21-01-2012, 04:55 PM
PSU IEEE Workshop on PIC Microcontrollers
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PIC Architecture: Background
Microprocessor:
Requires ‘external’ support hardware
E.g., External RAM, ROM, Peripherals.
Microcontroller:
Very little external support hardware.
Most RAM, ROM and peripherals on chip.
“Computer on a chip”, or “System on chip” (SOC)
E.g., PIC = Peripheral Interface Controller
PIC Architecture: Background
Traditionally, CPUs are “CISC”
Complex Instruction Set Computer (CISC)
Used in: 80X86, 8051, 68HC11, etc.
Many instructions (usually > 100)
Many, many addressing modes
Usually takes more than 1 internal clock cycle (Tcyc) to execute
Example:
The PIC Family: Speed
PICs require a clock to work.
Can use crystals, clock oscillators, or even an RC circuit.
Some PICs have a built in 4MHz RC clock
Not very accurate, but requires no external components!
Instruction speed = 1/4 clock speed (Tcyc = 4 * Tclk)
All PICs can be run from DC to their maximum spec’d speed:
