In different operating modes (Normal / Slow / Sleep), for SN8P2808, where is the system clock from?
1. SN8P2808 has two
external system clock sources: external high-speed OSC and external low-speed OSC
(32k), and one internal low-speed RC OSC.
2. In normal mode, system clock source（Fosc）is generated from external high-speed oscillator, LCD clock source is external 32768Hz oscillator crystal or RC and Watchdog clock source is internal low-speed oscillator.
3. In Slow mode, the external low-speed oscillator (32K) provides system clock source (Fosc) and the LCD clock source; if there is no external low-speed oscillator, instructions can not execute in slow mode.
4. In sleep mode, all clock sources will be disabled.
5. By controlling FSTPHX bit, user can only disable external high-speed oscillator, but can not stop external low-speed oscillator and internal low-speed oscillator.
2. In normal mode, system clock source（Fosc）is generated from external high-speed oscillator, LCD clock source is external 32768Hz oscillator crystal or RC and Watchdog clock source is internal low-speed oscillator.
3. In Slow mode, the external low-speed oscillator (32K) provides system clock source (Fosc) and the LCD clock source; if there is no external low-speed oscillator, instructions can not execute in slow mode.
4. In sleep mode, all clock sources will be disabled.
5. By controlling FSTPHX bit, user can only disable external high-speed oscillator, but can not stop external low-speed oscillator and internal low-speed oscillator.