The 2802x devices have two internal oscillators (INTOSC1 and INTOSC2) that need no external
components. They also have an on-chip, PLL-based clock module. Figure 3-6 shows the different options
that are available to clock the device.
Following are the input clock options available:
· INTOSC1 (Internal zero-pin Oscillator 1): This is the on-chip internal oscillator 1. This can provide
the clock for the Watchdog block, core and CPU-Timer 2
· INTOSC2 (Internal zero-pin Oscillator 2): This is the on-chip internal oscillator 2. This can provide
the clock for the Watchdog block, core and CPU-Timer 2. Both INTOSC1 and INTOSC2 can be
independently chosen for the Watchdog block, core and CPU-Timer 2.
· Crystal/Resonator Operation: The on-chip (crystal) oscillator enables the use of an external
crystal/resonator attached to the device to provide the time base. The crystal/resonator is connected to
the X1/X2 pins.
· External clock source operation: If the on-chip (crystal) oscillator is not used, this mode allows it to
be bypassed. The device clocks are generated from an external clock source input on the XCLKIN pin.
Note that the XCLKIN is multiplexed with GPIO19 or GPIO38 pin. The XCLKIN input can be selected
as GPIO19 or GPIO38 via the XCLKINSEL bit in XCLK register. The CLKCTL[XCLKINOFF] bit
disables this clock input (forced low). If the clock source is not used or the respective pins are used as