| 摘要 |
PROBLEM TO BE SOLVED: To obtain a low whole frequency division ratio by means of a high frequency division ration in a preceding frequency dividing period and the low frequency division ratio of a main frequency divider by providing a plurality of different frequency division ratios in the preceding frequency divider, arranging a lower-order second advance counter, by which the second frequency division ratio is set at the output side of the preceding frequency division unit and changing-over the frequency division ratio of the preceding frequency divider with another frequency division ratio by means of the counter. SOLUTION: A main counter M, by which the frequency division ratio M is set, is arranged at the output side of a quadro-modulus pre-scalar, having setting possible frequency division ratios 64/65/80/81. Also swallow counters A1 and A2 in the lower-order of the main counter M, by which the frequency division ratios A1 and A2 are set, are disposed at the output side of the pre- scalar. When each swallow counter A1 or A2 changes-over a 'dual modulus' pre-scalar from one frequency division mode into the other frequency division mode, the frequency division ratios M, A1 and A2 are adjusted effectively. Thus, the whole frequency division ratio N of each is obtained without interruption.
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