Patent Application
20080001635
The present invention relates to a data receiving circuit that receives a data signal input from another device and data receiving method thereof.
In receiving data with the use of a currently standardized serial interface, such as USB2.0, Serial ATA, or the like, the data is received only after input of the data is detected (see Non-patent Document 1 and Non-patent Document 2). This is because: with the use of a cable or the like for data transmission to and from another device, timing of data transmission cannot be determined well.
Recently, minimization of voltage amplitude of data, which progresses in association with an increase in speed of data transmission, necessitates determining whether an input signal is a data signal or a noise signal. Further, future increase in speed of data transmission will increase necessity of necessitate technique for noise discrimination. For this reason, a method of detecting input of an input signal is being increased in accuracy and functions (see Patent Document 1, for example).
Upon input of an input signal (DATA) to the data receiving circuit 500, the signal detector 501 first detects input of the input signal (DATA) and outputs, on the basis of the detection information, a start signal 50A for activating the signal receiver 502. The signal receiver 502 that has received the start signal 50A is activated to start receiving the input signal (DATA). The thus received input signal (DATA) is output as an output signal 50B to an internal circuit.
Patent Document 1: Japanese Patent Application Laid Open Publication No. 2000-196464 Non-patent Document 1: USB Revision 2.0 Specification, “Universal Serial Bus Specification,” retrieved on Oct. 14, 2004 in Internet (URL: http://www.usb.org/developers/docs/usb#20.zip, which is unzipped to “ . . . /USB#20/USB#20.pdf,” page 140
Non-patent Document 2: Serial ATA Specification retrieved on Oct. 14, 2004 in Internet (URL:http://www.sata-io.org/docs/PHYii%20Spec%20Rev%201#0%20052604.pdf, pp. 30-32
Detection of signal input in the signal detector requires time to thus disable data acquisition during the detection, so that the amount of missing data at a leading part of the input data increases. Further, in the case where data transmission is performed via a repeater, such as HUB or the like, such data missing occurs every time when data output from a data source passes through the repeater, making such adverse influence more serious.
The present invention has been made in view of the foregoing and has its object of suppressing data missing in receiving an input signal.
To attain the above object, in the present invention: input of an input signal is detected: whether the input signal is a data signal or a noise signal is determined; data receipt starts on the basis of the detection information; and when the input signal is determined as a data signal, the thus received input signal is output as a data signal.
Specifically, the present invention provides a data receiving device including a signal detector which detects an input state of an input signal and a signal receiver which receives the input signal, wherein the signal detector includes determination means for determining whether the input signal is a data signal or a noise signal, and the signal receiver includes: a receiving circuit which starts receiving the input signal when input of the input signal is detected in the signal detector; and a first logic circuit which outputs as a data signal a receiving signal received at the receiving circuit when the input signal is determined as a data signal in the signal detector.
Further, the present invention provides a data receiving method including the steps of: detecting an input state of an input signal; starting receiving the input signal when input of the input signal is detected; determining whether the input signal is a data signal or a noise signal; and outputting the received receiving signal as a data signal when the input signal is determined as a data signal.
As described above, according to the present invention, even though it takes time to determine an input signal as a data signal or a noise signal, missing of a top part of data can be suppressed to a minimum by utilizing each delay time of the receiving circuit and the logic circuit.
Embodiments of the present invention will be described below with reference to the accompanying drawings. The following preferred embodiments are substantially mere examples and are not intended to limit the present invention and applicable objects and usage thereof.
The signal detector 101 includes an input terminal IN which inputs a signal; an output terminal Sig_detect which outputs, on the basis of detection information of the input signal, a start signal that activates the signal receiver 102; and an output terminal Data_detect which outputs a determination result indicating whether the input signal is a data signal or a noise signal.
The signal receiver 102 includes a receiving circuit 103 that starts receiving the input signal upon receipt of the start signal output from the signal detector 101 and a first logic circuit 104 that controls output of an output signal on the basis of the determination result indicating whether the input signal is a data signal or a noise signal. The internal configurations of the signal detector 101 and the first logic circuit 104 will be described later.
Operation of the thus configured data receiving device 100 in accordance with Embodiment 1 will be described next. When the data receiving device 100 receives an input signal, the signal detector 101 detects the input state thereof and outputs a start signal for activating the signal receiver 102 from the output terminal Sig_detect on the basis of the detection information. Further, the signal detector 101 determines whether the input signal is a data signal or a noise signal and outputs the determination result from the output terminal Data_detect.
Upon receipt of the start signal, the receiving circuit 103 of the signal receiver 102 starts receiving the input signal. As well, the first logic circuit 104 receives the determination result and controls output of an output signal on the basis of the determination result. Specifically, when the input signal is determined as a data signal, the data signal is output as an output signal from the first logic signal 104. Otherwise, namely, when it is determined as a noise signal, output of the output signal is halted.
The data receiving circuit 100 utilizes delay times of the receiving circuit 103 and the first logic circuit 104 for determination as to whether the input signal is a data signal or a noise signal.
When the input signal is input to the signal detector 101, a first offset comparator 110 senses the size of the positive amplitude of the input signal while a second offset comparator 111 senses the size of the negative amplitude of the input signal.
Sensing results that the first and second offset comparators 110, 111 sense are input to an OR circuit 112, are filtered in first and second filter circuits 113, 114, respectively, and then are output as the start signal and the determination result. The time constants for filtering in the first and second filter circuits 113, 114 are changed so as to obtain desired outputs.
Upon input of the signal to each of the first and second filter circuits 113, 114 from the OR circuit 112, the switch 117 is turned on to allow the capacitor 118 to discharge charges so that the comparator 119 senses a potential varied according to the amount of the discharged charges and the capacity of the capacitor 118.
Change in flow rate of the second current source 116 or in capacity of the capacitor 118 changes a time constant. Specifically, in the first filter circuit 113, the flow rate of the second current source 116 is set large for reducing time required from input detection of the input signal to output of the detection result. It is noted that the same effects can be obtained even when the second current source 116 is removed for terminal contraction thereof.
It is also noted that the comparator 119 provided for comparing the input voltage is not limited to the aforementioned type and may be replaced by an inverter, for example.
The delay circuit 140 performs control so that input timing that the signal received at the receiving circuit 103 is input is adjusted and then the thus received signal is output to the AND circuit 141.
Specifically, in the case where it takes time to determine whether the input signal is a data signal or a noise signal and input of the determination result to the AND circuit 141 is hung on, the delay amount of the delay circuit 40 is set large to delay the input timing of the signal received at the receiving circuit 103. In the case where the delay at the receiving circuit 103 is sufficient with no further delay necessitated, the delay circuit 140 is omitted.
It is noted that the delay circuit 140 may be replaced by a circuit having another function, such as pattern matching, synchronization of a receiving signal with the internal clock, or the like to utilize delay thereof.
When the input signal is determined as a data signal, the AND circuit 141 outputs, on the basis of the determination result output from the signal detector 101, the data signal received at the receiving circuit 103 as an output signal. Otherwise, namely, when it is determined as a noise signal, output of the output signal is halted.
Though the data receiving device of Embodiment 1 presumes that the receiving signal in data transmission under USB2.0 or Serial ATA is a serial differential signal, the present invention is not limited thereto. The same is applied to Embodiments 2 to 4 described below.
When an input signal is input to the signal detector 201, the first offset comparator 110 senses the size of the positive amplitude of the input signal while the second offset comparator 111 senses the size of the negative amplitude of the input signal.
Sensing results sensed in the first and second offset comparators 110, 111 are input to the OR circuit 112 and is filtered in the first filter circuit 113, and then, an output signal thereof is output as the start signal from the output terminal Sig_detect while being input to an AND circuit 124 and a counter 125.
The AND circuit 124 receives the filtered signal and a CLK signal and inputs a resultant output thereof to the counter 125. The counter 125 exactly measures, on the basis of the filtered signal and the resultant output from the AND circuit 124, a time period when the input signal has an amplitude larger than Vt1. The input signal is determined as a data signal or a noise signal on the basis of the measurement result, and a determination result is output from the output terminal Data_detect.
A sensing result sensed in the first offset comparator 110 is input to the first filter circuit 113 to be filtered. The thus filtered signal is input to an OR circuit 134 and a second logic circuit 135.
On the other hand, a sensing result sensed in the second offset comparator 111 is input to the second filter circuit 114 to be filtered. The thus filtered signal is input to the OR circuit 134 and the second logic circuit 135.
The OR circuit 134 performs input detection of the input signal on the basis of the signals input from the first and the second filter circuits 113, 114 and outputs the start signal from the output terminal Sig_dtect.
The second logic circuit 135 determines whether the input signal is a data signal or a noise signal on the basis of the signals input from the first and second filter circuit 113, 114.
Specifically, the data determination is performed by judging whether state transition of the input signal occurs within a predetermined time period. The state transition means transition from a “High” state that the input signal has a large positive amplitude to a “Low” state that it has a large negative amplitude or from the “Low” state to the “High” state.
During the time when the above state transition occurs, the signals filtered by the filter circuits 113, 114 have large amplitude. Accordingly, the second logic circuit 125 detects the filtered signals to sense the state transition between “Low” and “High.”
The first logic circuit 204 includes a clock data recovery circuit 150 (hereinafter referred to it as a CDR circuit) which synchronizes a receiving signal with an internal clock and a shift resistor 151.
The CDR circuit 150 receives the input signal received at the receiving circuit 103. Upon receipt of a CLK signal from outside, the CDR circuit 150 inputs the input signal held in the receiving circuit 103 to the shift resistor 151.
The shift resistor 151 receives from an EN terminal thereof the determination result indicating whether the input signal is a data signal or a noise signal. When the input signal is determined as a noise signal, the shift resistor 151 is reset. Otherwise, namely, it is determined as a data signal, the reset state is released so that the shift resistor 151 outputs the data signal as an output signal.
Though the CDR circuit 150 is inserted in the first logic circuit 204 for adjusting timing between data and a clock input to the shift resistor 151, the CDR circuit 150 may be omitted if the timing adjustment is unnecessary. The shift resistor 151 may be replaced by another data storage circuit, of course.
As described above, the data receiving device with the clock in accordance with Embodiment 4 guarantees the hold time of a receiving signal further exactly and is, therefore, useful especially in the case where it is complicated and takes time to determine whether a signal is data or noise in the signal detector 101.
As described above, the data receiving device in accordance with the present invention suppresses data missing of a leading part of a data signal to a minimum. Further, receipt of an input signal is performed in parallel with determination as to whether the input signal is a data signal or a noise signal, so that the time period from input to output of the input signal can be reduced when compared with serial processing where determination as to whether the input signal is a data signal or a noise signal is performed only after the input signal is received. Accordingly, this effect is much practical, and therefore, the present invention is useful and has significant industrial applicability.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2004-381602 | Dec 2004 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP05/15567 | 8/26/2005 | WO | 6/28/2007 |
