OSC4M

Introduction

The OSC4M (ANA4M) of chip is used to provide 4MHz clock for CPU, or 2MHz clock for peripherals after frequency division.

Features

• Error: ±3%

• Self-power consumption: 7uA

• Can divide the frequency according to the divider coefficient

Functional Description

Block Diagram

OSC4M block diagram is shown below.

OSC4M Control

在系统active时 PMC 会推出 cke_LP4M, OSC4M一定是ON 的状态, 在系统sleep时, PMC 会根据sw的option (是否在sleep下保持OSC4M常开) 来推出OSC4M的CLK。

HW (WIFI/BT/SDM/ADC) 会根据 HW的需求去request (电平信号) 打开OSC4M。并且在对应HW 不再需要使用OSC4M后, HW 会cancel掉request。

对于类似loguart/uart等在sleep期间需要OSC always on的的IP, 如果需要再sleep期间工作, 需要software 配置SW option来请求PMC request OSC4M always on。