10.10 Start-up Sequence

Upon the release of a POR or BOR, the following must occur before the device will begin executing:

  1. Power-up Timer runs to completion (if enabled).
  2. Oscillator start-up timer runs to completion (if required for selected oscillator source).
  3. MCLR must be released (if enabled).

The total time-out will vary based on oscillator configuration and Power-up Timer configuration.

The Power-up Timer and oscillator start-up timer run independently of MCLR Reset. If MCLR is kept low long enough, the Power-up Timer and oscillator Start-up Timer will expire. Upon bringing MCLR high, the device will begin execution after ten FOSC cycles (see Figure 10-4). This is useful for testing purposes or for synchronizing more than one device operating in parallel.

Figure 10-4. Reset Start-up Sequence