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System Clock

The System Clock (shown as “CLOCK” in the Block Diagram P8X32A) is the central clock source for nearly every component of the Propeller chip.  The System Clock’s signal comes from one of three possible sources:

  1. The Internal RC Oscillator
  2. The Clock Phase-Locked Loop (PLL)
  3. The Crystal Oscillator (an internal circuit that is fed by an external crystal or crystal/oscillator pack.) 

The source is determined by the CLK Register settings, which is selectable at compile time and adjustable at run time.  The only components that don’t use the System Clock directly are the Hub and Bus (see the Block Diagram P8X32A); they divide the System Clock by two (2).

Propeller Help Version 1.1

Copyright © Parallax Inc.

5/13/2009