| 摘要 |
PURPOSE:To secure electromagnetic compatibility EMC by spreading the frequency spectrum of a generated clock. CONSTITUTION:A carrier generating circuit 1 supplies a double frequency signal 2f0 of a carrier f0 to a D flip-flop FF2 and divides the frequency into two so as to obtain the f0, and the frequency is divided into N with a frequency dividing ratio N, which is set at a programmable register 16, by a frequency divider 3 and supplied to a pseudo random code generator 4 as a fundamental clock. Based on the fundamental clock f0/N, a wave to be modulated is outputted so that the half value width of the frequency spectrum can be more than 60KHz. The f0 of the wave to be modulated of the generator 4 are supplied to a phase modulator 5 and the obtained modulated wave is supplied to the D terminal of a DFF 6. Then, the pulse less than the half of the f0 to be generated by modulation is removed and the processed modulated wave is supplied to a central processing unit 7 as a control clock. Then, the unit 7 outputs a control signal for setting the frequency dividing ratio N to the register 16. Thus, since the malfunction of the unit 7 can be prevented, the EMC can be secured in an equipment applied for a computer. |
