# Are there provisions in switching clock division ratio selection bit?

Latest Updated:08/05/2009

## Question:

(CPU, Clock)

Are there any precautions about switching the clock division ratio selection bits? [2009/08/05]

Are there any precautions about switching the clock division ratio selection bits? [2009/08/05]

## Answer:

Please change the values of the clock division ratio selection bits at the same time using a single instruction.

Example using the 7546 Group:

When changing from on-chip oscillator (10) to middle-speed mode (01), if you switch the clock division ratio selection bits one at a time, you will transition through other states such as high-speed mode (00) or double-speed mode (11). Recommended operating voltage differs by frequency, so care is required.

(#107430)

**Suitable Products**

3803H |

3803L |

3850A |

3858 |

38D2 |

38D5 |

7544 |

7545 |

7546 |

7547 |

7548 |

7549 |