| 摘要 |
<p>PURPOSE:To attain the normal operation of a supply system for common clock signals by constituting a clock oscillation circuit in a module as a PLL circuit to attain the exchange between the 1st and 2nd functions and therefore maintaining the synchronization between modules through a common clock generating circuit even through the common clock generating circuit has a permanent trouble. CONSTITUTION:A crystal oscillation circuit can produce a low frequency with switches 33 and 34 turned on, an intermediate frequency with switches 33 and 34 turned on and off respectively and a high frequency with switches 33 and 34 turned off respectively with the discrete change of frequencies. When a module where the coincidence must be secured with satisfactorily high accuracy among the intermediate frequencies of all clock oscillation circuits in the module serves as a supply source for common clocks, 1 is supplied to a signal line 39. Thus the switches 33 and 34 are turned on and off respectively and the oscillation circuit oscillates with the intermediate frequency. Then a common clock signal 36 is delivered onto a common clock line and the oscillation circuit serves as a supply source for common clock signals to all other modules.</p> |
