| 摘要 |
PURPOSE:To constitute a frequency phase synchronizing circuit with a digital circuit and to make it into a digital IC by performing the prescribed frequency dividing operation of a crystal oscillation output frequency for each rise of reference clocks from a line connection device and keeping frequency fluctuation within one clock. CONSTITUTION:In this information transfer frequency conversion circuit, the reference crocks 8KHz 3 generated in an SP conversion circuit are inputted to this frequency phase synchronizing circuit 14. The rise of the reference clocks 3 is detected in an edge detection circuit 23, frequency divider circuits 25-27 are initialized by a reset pulse 8 and then, the clocks 9 of 12.288MHz which are the output of a crystal oscillator 24 are successively frequency divided into 8, 24 and 8. Then, at 1535th frequency division from initialization, the operation of the frequency divider circuits is stopped by a timing generation circuit 28 and the clocks 4, 5 and 6 corresponding to the respective frequency divider circuits synchronized with the reference clocks 3 are obtained. At the time, 1535th frequency division from the reset pulse 8 is before the next reset pulse 8 and the next reset pulse 8 is outputted by the clock 9 within 1-2 clocks. |
