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Boot Up Procedure

Upon power-up (+ 100 ms), RESn low-to-high, or software reset:

  1. The Propeller chip starts its internal clock in slow mode (≈ 20 kHz), delays for 50 ms (reset delay), switches the internal clock to fast mode (≈ 12 MHz), and then loads and runs the built-in Boot Loader program in the first processor (Cog 0).
  2. The Boot Loader performs one or more of the following tasks, in order:
    1. Detects communication from a host, such as a PC, on pins P30 and P31.  If communication from a host is detected, the Boot Loader converses with the host to identify the Propeller chip and possibly download a program into Main RAM and optionally into an external 32 KB EEPROM.
    2. If no host communication was detected, the Boot Loader looks for an external 32 KB EEPROM (24LC256) on pins P28 and P29.  If an EEPROM is detected, the entire 32 KB data image is loaded into the Propeller chip’s Main RAM.
    3. If no EEPROM was detected, the boot loader stops, Cog 0 is terminated, the Propeller chip starts the Shutdown Procedure, and all I/O pins are set to inputs.
  3. If either step 2a or 2b was successful in loading a program into the Main RAM, and a suspend command was not given by the host, then Cog 0 is reloaded with the built-in Spin Interpreter and the user code is run from Main RAM.

Propeller Help Version 1.1

Copyright © Parallax Inc.

5/13/2009