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Compensated-clock generating circuit and usb device having same

A technology of clock generation circuit and generation circuit, which is applied in the direction of electric pulse generator circuit, generation/distribution signal, pulse generation by differential amplifier, etc., can solve the problem of unsatisfactory frequency accuracy of the oscillator, and achieve the effect of low cost

Inactive Publication Date: 2007-04-04
NEC ELECTRONICS CORP
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  • Abstract
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Problems solved by technology

However, the frequency accuracy of the oscillators built into the microcomputers used in these terminals does not satisfy this point, and the accuracy needs to be improved.

Method used

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  • Compensated-clock generating circuit and usb device having same
  • Compensated-clock generating circuit and usb device having same
  • Compensated-clock generating circuit and usb device having same

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Embodiment Construction

[0045] A characteristic configuration of what should be called the concept of the present invention will be described with reference to FIG. 2 . The corrected clock generation circuit 1 of the present invention includes an oscillation circuit 11 , a counting circuit 2 for counting the number of clock pulses of the oscillation circuit 11 , and a frequency correction value generation circuit 16 . It also includes a functional block 3 that generates regular and given signals related to USB downstream signals. A specific example of the functional block 3 will be described later. The counting circuit 2 further includes, for example, a counter 14 for counting the number of clock pulses of the oscillation circuit, and a count value memory 15 capable of storing the number of clock pulses counted by the counter 14 . The frequency correction value generation circuit 16 stores a predetermined reference value of the number of clock pulses of the oscillation circuit 11 in advance, compare...

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Abstract

A compensated-clock generating circuit that complies with USB specifications includes an oscillating circuit that generates clock pulses; a counting circuit that counts the number of clock pulses from the oscillating circuit based upon a regular prescribed signal in accordance with a USB downstream signal; and a frequency compensation value generating circuit that compares the value counted by the counting circuit and a prescribed reference value and obtaining a compensation value. The oscillation frequency of the oscillating circuit is corrected to a prescribed value in response to receipt of the compensation value from the frequency compensation value generating circuit. Compensation is applied based upon a highly accurate signal that is based upon USB specifications, thereby making it possible to generate pulses of higher accuracy even if the accuracy of the oscillation frequency per se of the oscillator in the oscillation circuit is low.

Description

technical field [0001] The present invention relates to a corrected clock generating circuit, in particular to a corrected clock generating circuit realizing frequency accuracy complying with the USB specification and a USB device equipped with the same. Background technique [0002] Recently, in personal computers (PCs) and the like, the USB specification has been popularized. Therefore, terminals such as keyboards, mice, and scanners also require the transfer rate of data to be within a given accuracy in compliance with the USB specification. Generally, these terminals that meet the USB specification are called USB devices. The USB specification has various cases such as low speed and full speed. As an example, the widely used full speed requires an accuracy of ±0.25% of the data transfer speed. In order to satisfy this value, it is of course necessary to make the clock more accurate than this value. For this reason, a method of using a high-precision external crystal r...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): G06F1/04H03L7/00H03K3/023
CPCH03L7/091H03L7/181G06F13/426H03L7/00
Inventor 冈田绘美沟口诚
Owner NEC ELECTRONICS CORP
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