1. Field of the Invention
This application claims priority from Japanese Patent Application No. 2007-334547, filed Dec. 26, 2007, the disclosure of which is herein incorporated in its entirety. The present invention relates to a transmission characteristic adjustment device, a circuit substrate, and a transmission characteristic adjustment method that adjust a transmission characteristic between a transmission element and a reception element having a transmission path interposed therebetween. In particular, the present invention relates to a transmission characteristic adjustment device, a circuit substrate, and a transmission characteristic adjustment method that monitor deterioration of waveform quality in an input of a reception element of a signal transmission system with a window width in a time axis direction measured by using a multiphase CLK as an index, and use a result of the monitoring to adjust a transmission characteristic.
2. Description of the Related Art
In recent years, along increase in speed of signal transmission, there is a tendency that a margin thereof (waveform margin) becomes smaller. Accordingly, there has been increased need for sequential adjustment of a transmission characteristic with respect to proper locations on a device, not only in design and evaluation stages.
In contrast, a technique which has been conventionally provided adopts a system that adjusts any circuit element to adjust a transmission characteristic while monitoring an error factor. For example, as a reference document, there is a Patent Document such as Jpn. Pat. Appln. Laid-Open Publication No. 2003-032187.
However, when a circuit element is adjusted while an error factor is monitored, an error factor of a certain degree needs to be tolerated. Accordingly, there has been a problem that the conventional technique can only be applied to a system that can tolerate an error factor of a certain degree.
The present invention has been made in order to solve the problem described above. An object of the present invention is to provide a transmission characteristic adjustment device with high reliability in a transmission characteristic that can adjust a circuit before an error occurs and never generates an error, a circuit substrate incorporating such a transmission characteristic adjustment device, and a transmission characteristic adjustment method.
In order to achieve the object described above, according to an aspect of the present invention, there is provided a transmission characteristic adjustment device that adjusts a transmission characteristic between a transmission element and a reception element with a transmission path interposed therebetween. The transmission characteristic adjustment device includes a determination section that determines existence or non-existence of a difference with respect to confirmed data based on each phase of a multiphase clock. Also, the transmission characteristic adjustment device includes a window detection section that detects a window width in a time axis direction of receiving data based on a result of determination of the determination section and a phase of the multiphase clock. Further, the transmission characteristic adjustment device includes a circuit element setting section that evaluates a setting value of a circuit element of the transmission element or the reception element that has an influence on a receiving waveform based on a fluctuation of the window width detected by the window detection section, and changes the setting value of the circuit element of the transmission element or the reception element based on a result of the evaluation.
In addition, according to an aspect of the present invention, there is provided a circuit substrate having a transmission characteristic adjustment device that adjusts a transmission characteristic between a transmission element and a reception element with a transmission path interposed therebetween. The transmission characteristic adjustment device includes a determination section that determines existence or non-existence of a difference with respect to confirmed data based on each phase of a multiphase clock. Also, the transmission characteristic adjustment device includes a window detection section that detects a window width in a time axis direction of receiving data based on a result of determination of the determination section and a phase of the multiphase clock. Further, the transmission characteristic adjustment device includes a circuit element setting section that evaluates a setting value of a circuit element of the transmission element or the reception element that has an influence on a receiving waveform based on a fluctuation of the window width detected by the window detection section, and changes the setting value of the circuit element of the transmission element or the reception element based on a result of the evaluation.
Further, according to an aspect of the present invention, there is provided a transmission characteristic adjustment method that adjusts a transmission characteristic between a transmission element and a reception element with a transmission path interposed therebetween. The transmission characteristic adjustment method determines existence or non-existence of a difference with respect to confirmed data based on each phase of a multiphase clock. Also, the transmission characteristic adjustment method detects a window width in a time axis direction of receiving data based on a result of the determination and a phase of the multiphase clock. Further, the transmission characteristic adjustment method evaluates a setting value of a circuit element of the transmission element or the reception element that has an influence on a receiving waveform based on a fluctuation of the detected window width, and changes the setting value of the circuit element of the transmission element or the reception element based on a result of the determination.
According to the present invention, evaluation of setting can be carried out based on a fluctuation of a detected window width in a time axis direction, and a transmission characteristic can be adjusted depending on a result of the evaluation. Accordingly, an advantageous effect that transmission with high reliability can always be carried out can be achieved.
Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.
The transmission element 100 includes an internal processing circuit 101 and an output buffer 102 that outputs a result of processing of the internal processing circuit 101 to the transmission path.
In addition, the reception element 200 includes receiving systems RA and RB, a path switching circuit 203, and an internal processing circuit 204. The RA and RB include equalizers 201A and 201B and input buffers 202A and 202B.
Then, the receiving system RB, which is one of the two receiving systems RA and RB, includes a multiphase clock generator 205, a time axis window width monitoring circuit (time axis window width detection section) 206, and a circuit element adjustment circuit (circuit element adjustment section) 207. The multiphase clock generator 205 generates a multiphase clock. The time axis window width monitoring circuit 206 detects a time axis window width. The circuit element adjustment circuit 207 detects a fluctuation of the window width detected by the time axis window width monitoring circuit 206, evaluates a setting value of a circuit element (the equalizer 201B in this case) that has an influence on a window width, and adjusts the equalizer 201B (the setting value of a circuit element) based on a result of the evaluation.
Hereinafter, detailed description of the above will be made. The transmission path 300 is a line that connects the transmission element 100 and the reception element 200. More specifically, the transmission path 300 is made of a printed wiring substrate, a cable, and the like.
The equalizers 201A and 201B are circuits that compensate a high frequency component lost in the transmission path from the reception element 200 side.
The multiphase clock generator 205 generates a CLK that is obtained by fluctuating a phase by a time width that is obtained by dividing one cycle by any number.
The time axis window width monitoring circuit 206 measures a window width on a time axis by confirming input data by a CLK of each phase that is supplied from a multiphase CLK, and recognizing a section where logic of adjacent phases is different as a data change point. The time axis window width monitoring circuit 206 may be configured to measure a window width and monitor a fluctuation of the window width.
The circuit element adjustment circuit 207 detects a fluctuation of a window width measured by the time axis window width monitoring circuit 206, and evaluates a setting value of the equalizer 201B based on the fluctuation. Then, the circuit element adjustment circuit 207 changes and adjusts a setting value of the equalizer 201B based on a result of the evaluation. The above adjustment is carried out so that a width of a time axis window becomes maximum. In the present embodiment, the circuit element adjustment circuit 207 is provided with a function of detecting a fluctuation of a window width. However, as described above, the function may be provided in the time axis window width monitoring circuit 206.
Hereinafter, description will be made with respect to entire operation of the embodiment 1 by using a flowchart of
(Detection of Data Change Point: S1)
A system of detecting a data change point is a system that is adopted by a general clock recovery circuit. A specific process will be described below.
(First Step) Generation of a Multiphase Clock
As shown in
(Second Step) Logic Confirmation in Each Phase Clock
As shown in
(Third Step) Detection of a Section where Logic is Different Between Adjacent Phases
As shown in
(Calculation of Time Axis Window Width: S2)
As shown in
(Monitoring of Fluctuation of Time Axis Window Width: S3)
As shown in
(Adjustment of Circuit Element: S4)
Adjustment of a circuit element is carried out by steps described below.
Setting of an amplification amount (hereinafter represented as the equalizer amount) with respect to a high frequency component of an equalizer circuit is set to an initial value of “0” (S4-1). Then, a time axis window width is measured (S4-2). Next, setting of the equalizer amount is changed to a next stage in an increasing direction (S4-3). Then, a time axis window width is measured (S4-4).
The processing of the above steps (S4-3) and (S4-4) is applied to all setting values (S4-5). Then, setting in which a window width becomes maximum is detected, and the detected setting is set as an adopted value (S4-6).
(Reflection of Setting: S5)
The setting detected in the above section (S4) is reflected to a circuit.
At this time, the circuit needs to be controlled so that there is no error generated along the change of setting. This function is included in a path switching circuit included in an operation conceptual view shown in
First, the extracted setting is reflected to a Sub system RB shown in
Then, when the coincidence of the Main system and the Sub system is confirmed (S5-2), the Sub system is selected as the receiving data (S5-3). Then, setting of the Sub system is reflected to the Main system (S5-4). Then, when settlement of an error at the time of switching setting of the Main system is confirmed by the coincidence of the receiving data of the Sub system and the Main system (S5-5), the Main system is selected as the receiving data (S5-6).
In the first embodiment, an equalizer is adopted as a circuit element adjusted by a circuit element, that is, the circuit element adjustment circuit 207, which controls a transfer characteristic. A similar advantageous effect can be obtained by controlling the transmission element 100 and the reception element 200.
For example, as shown in
In addition, in a third embodiment, as setting of a circuit element, a transmission system of a transmission element 100A can be made redundant. In the first embodiment described above, a redundant circuit is configured only with the reception element side. Accordingly, a circuit element on the transmission side cannot be adjusted.
In view of the above, as shown in
In
In the first embodiment, the signal transmission system is divided into two systems (Main and Sub), and a function of adjusting a circuit element is included in the Sub side. According to the above configuration, when setting is switched, steps of Main-Sub-Main in this order are necessary as shown in
In the first embodiment, as shown in
In the third embodiment, the description was made with respect to redundancy of the transmission element. As shown in
In contrast, as shown in
As shown in
When an error due to a jitter is generated in a signal transmission system, a jitter frequency causing the error is often limited. Then, the jitter is often generated by noise that is trapped in a power supply system of the PLL 261. Therefore, a variable element (a condenser, or an inductance) 262 is included in the inside of a power supply terminal to the PLL 261. Then, a characteristic of a filter that is determined by composition of the internal element and an external power source filter (a filter circuit) 263 prepared externally is changed. In this manner, the jitter causing the error can be restricted.
As described above, according to the present invention, adjustment of a transfer characteristic can be attempted while a result is being checked. Also, since measurement of a margin is configured with a digital circuit, application to an LSI is facilitated. Accordingly, an advantageous effect that the present invention can contribute to improvement in quality of signal transfer can be achieved.
As described above, according to the present embodiment, adjustment of a transfer characteristic can be attempted while a result is being checked. Also, since measurement of a time axis window width is configured with a digital circuit, application to an LSI is facilitated. Accordingly, an advantageous effect that the present invention can contribute to improvement in quality of signal transfer can be achieved.
Number | Date | Country | Kind |
---|---|---|---|
2007-334547 | Dec 2007 | JP | national |
Number | Name | Date | Kind |
---|---|---|---|
3806804 | Mills et al. | Apr 1974 | A |
5717510 | Ishikawa et al. | Feb 1998 | A |
6993083 | Shirakata et al. | Jan 2006 | B1 |
7020399 | Miyata et al. | Mar 2006 | B1 |
7123846 | Tateyama et al. | Oct 2006 | B2 |
7199615 | Stojanovic et al. | Apr 2007 | B2 |
7529300 | Richards | May 2009 | B2 |
7555276 | Wilcox | Jun 2009 | B2 |
7733967 | Yamazaki | Jun 2010 | B2 |
7764935 | Pallonen et al. | Jul 2010 | B2 |
20070025465 | Richards | Feb 2007 | A1 |
20070142014 | Wilcox | Jun 2007 | A1 |
20080153433 | Pallonen et al. | Jun 2008 | A1 |
20090028074 | Knox | Jan 2009 | A1 |
20090274072 | Knox | Nov 2009 | A1 |
20100225401 | Hayata et al. | Sep 2010 | A1 |
Number | Date | Country |
---|---|---|
04-017432 | Jan 1992 | JP |
8-321805 | Dec 1996 | JP |
2003-32187 | Jan 2003 | JP |
2004-104440 | Apr 2004 | JP |
Number | Date | Country | |
---|---|---|---|
20090167452 A1 | Jul 2009 | US |