9.10 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 10 FOSC cycles (see figure below). This is useful for testing purposes or to synchronize more than one device operating in parallel.

Figure 9-4. Reset Start-up Sequence