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EP0560320A1
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Clock generator
Assignee: NEC Corp
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Filing: 1993-03-10
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Granted: —
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Expires: 2013-03-10
Abstract
Abstract If, in a clock generator according to the present invention, the first clock is switched to the second clock with a lower frequency, a frequency count circuit (40) counts the frequency of the second clock with using the first clock as reference. A clock switching control circuit (60) judges whether the frequency of the second clock is stable or not based on the count result from said frequency count circuit (40) and, if it is stable, switches a switching circuit (30) for clock switching to the second clock.
Inventors
- 👤 Tomiyori c/o NEC Corporation Yutaka
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-05 16:32
CPC Classifications
H; H03; H03K; H03K5/00; G; G06; G06F; G06F1/00; G06F1/04; G06F1/08
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
80 words
A clock generator comprising: a plurality of clock generation means (10),(20) for generating a plurality of clocks having different frequencies, a clock switching means (30) for selectively outputting one of said plurality of clocks, and a clock switching control means which, in switching from the current clock to the other clock with a different frequency, judges whether the frequency of the new clock is stable or not and, if it is stable, controls said switching means (30) for clock switching.
Claim 2
Dependent Claim
42 words
A clock generator of Claim 1 further comprising a frequency count circuit (40) which counts the frequency of said new clock with using said current clock as the reference and outputs the counted frequency data to said clock switching control means (60).
Claim 3
Dependent Claim
82 words
A clock generator of Claim 2 wherein said clock switching control means (60) during clock switching processing, oscillates the clock generation means (10),(20) for the new clock, obtains the frequency of said new clock counted by said frequency count circuit (40) at certain timing, judges whether the frequency of said new clock is stable or not, switches said switching means (30) to said new clock when the frequency is stable and terminates said current clock generation means (10),(20) after completion of switching.
Claim 4
Dependent Claim
47 words
A clock generator as claimed in any of Claims 1 to 3 wherein said clock switching control means (60) stores a predetermined frequency range where the new clock can be considered stable and judges whether the frequency from said frequency counter is in said stored frequency range.
Claim 5
Dependent Claim
123 words
A clock generator comprising: a first clock generation means (10) to generate a first clock, a second clock generation means (20) to generate a second clock having a frequency different from that of said first clock, a clock switching means (30) to selectively output either of said first or second clock, a frequency count circuit (40) to count the frequency of said second clock with using said first clock as reference, and a clock switching control means (60) which, in switching from said first clock to said second clock, judges whether the frequency of said second clock is stable or not based on the count result from said frequency count circuit (40) and switches said switching means (30) when the frequency is stable.
Claim 6
Dependent Claim
95 words
A clock generator of Claim 5 wherein said clock switching control means (60), during switching from said first clock to said second clock, oscillates said clock generation means (20) for said second clock, obtains said second clock frequency counted by said frequency count circuit (40) at certain timing, judges whether the frequency of said second clock is stable or not, switches said switching means (30) to said second clock when the frequency of said second clock is stable and terminates said first clock generation means (10) after completion of switching by said switching means (30).
Claim 7
Dependent Claim
44 words
A clock generator of Claim 5 or 6 wherein said clock switching control means (60) stores a predetermined frequency range where the second clock can be considered stable and judges whether the frequency sent from said frequency counter is in said stored frequency range.
References Cited (Backward Citations)
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