SN8F5708 datasheet(47/204 Pages) SONIX

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SN8F5708 Series

System Clock and Power Management

Datasheet Rev. 2.4

8.3 Noise Filter

The Noise Filter controlled by Noise Filter option is a low pass filter and supports crystal mode. The

purpose is to filter high rate noise coupling on high clock signal from external oscillator. In high

noisy environment, enable Noise Filter option is the strongly recommendation to reduce noise

effect.

8.4 Power Management

After the end of reset signal and power-on sequence, the CPU starts program execution at the

speed of fcpu. Overall, the CPU and all peripherals are functional in this situation (categorized as

normal mode).

The least two bits of PCON register (IDLE at bit 0 and STOP at bit 1) control the microcontroller’s

power management unit.

If IDLE bit is set by program, only CPU clock source would be gated. Consequently, peripheral

functions (such as timers, PWM, and I2C) and clock generator (IHRC 32 MHz/crystal driver) remain

execution in this status. Any change from P0/P1 input and interrupt events can make the

microcontroller turns back to normal mode, and the IDLE bit would be cleared automatically.



Any function can work in IDLE mode. Only CPU is suspended



The IDLE mode wake-up sources are P0/P1 level change trigger and any interrupt event.

If STOP bit is set, by contrast, CPU, peripheral functions, and clock generator are suspended. Data

storage in registers and RAM would be kept in this mode. Any change from P0/P1 can wake up the

microcontroller and resume system’s execution. STOP bit would be cleared automatically.



CPU, peripheral functions, and clock generator are suspended.



The STOP mode wake-up source is P0/P1 level change trigger.

For user who is develop program in C language, IDLE and STOP macros is strongly recommended to

control the microcontroller’s system mode, instead of set IDLE and STOP bits directly.

IDLE();

STOP();



Note: Into IDLE mode or STOP mode by “Assembly Language” must be using MOV

instruction.

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