JP2005333533A - Resync apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve a problem that an optimal phase change may not be performed upon a succeeding signal if it is set to perform the phase change on the basis of a signal when a phase is affected by jitter or noise considerably. <P>SOLUTION: In a phase determination apparatus 101 which determines a phase of an operating clock DQS1 from a system clock SCLK1 and the operating clock DQS1 of a device 1, the phase is notified to a noise determination section 103 for determining whether or not the phase of the operating clock DQS1 is affected by noise or jitter. The noise determination section 103 stores one or more phase signals of the operating clock DQS1 notified in the past, it is determined based on the history in the past whether or not phase information Ph1 is affected by great jitter or noise, and a signal Ph2 indicative of correct phase information is notified to the phase determination apparatus 101. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  In a signal transmission system, in general, the phase of a transmission signal is detected between devices that transmit and receive signals, and the phase of the transmitted signal is changed to a phase that can be received by a receiving device to perform signal transmission. In this specification, this operation is described as “resync”, and a device having a function of performing “resync” is described as a “resync device”.

  The present invention relates to a device in which a function for preventing signal transmission and reception from failing due to jitter and noise is added to a resync device.

  In general, it is known that a resync apparatus determines how many phases of a transmitted signal are, and a receiving apparatus determines how many phases are to be changed (for example, refer to Patent Document 1). ). The outline of the resync apparatus will be described with reference to FIGS.

  FIG. 8 is a diagram showing a case where the resync apparatus Re is applied to the signal transmission system including the apparatus S and the apparatus R. The signal s_s is transmitted from the apparatus S, and the signal s_s is transmitted to the apparatus R in the resync apparatus Re. It is an example which shows the system changed into phase s_r which can be received by (1).

  FIG. 9 is an example of a table showing the phase for changing the received signal, with respect to a resync apparatus that can detect the signal phase with a resolution of 90 degrees and can change the phase with a resolution of 90 degrees. When the resync apparatus Re in FIG. 8 is a resync apparatus having the characteristics of FIG. 9, when the phase of the signal s_s in FIG. 8 is between 0 degrees and 90 degrees, the resync apparatus Re can be received by the apparatus R at 270 degrees. The signal s_r whose phase is changed to is transmitted to the device R.

  In the resync device, in order to reduce the scale of the device, the phase of all received signals is detected, and instead of changing to a phase suitable for each, the operation of detecting the phase of the signal once is performed several times. The phase for changing the phase of the signal received at this time is determined. Hereinafter, this operation is described as “resync training”.

In this way, transmission / reception of signals, particularly high-frequency signals, is performed between the transmitting and receiving devices by performing retraining by the resync device.
JP 2003-224550 A

  In a signal transmission system operating at a high frequency, noise and jitter have a large influence on the phase. For this reason, if the signal referred to when performing restraining by the resynchronizer device changes the original phase due to the influence of noise or jitter, there is a possibility that subsequent signal transmission may fail.

  For example, in the system of FIGS. 8 and 9, when the signal s_s has an average phase of 100 degrees, for example, the resync device Re needs to be set to change the signal s_s to 0 degrees according to FIG. However, when resync training is performed, the phase of the signal s_s sometimes exceeds 180 degrees due to large jitter or noise. In this case, the resync apparatus Re performs setting to change the phase by 90 degrees according to the table of FIG.

  However, the signal s_s may sufficiently change to a phase smaller than 90 degrees due to small jitter or noise. In this case, the resync device Re needs to change the phase to 270 degrees according to the table of FIG. 9, but has already been set to change the phase to 90 degrees. The difference expands to 180 degrees. Even if the signal phase tolerance of the device R is ± 90 degrees, the signal s_s cannot be received in this case. As described above, in the current resync apparatus, when the retraining is performed, the signal that is referred to is subjected to a large jitter or noise, so that the signal may not be received. There is.

  In recent years, signal transmission systems have increased in operating frequency, and it is expected that the influence of jitter and noise on the phase of the signal will continue to increase. A resync device corresponding to jitter and noise is required.

  If the restraining is performed when the influence of jitter or noise on the phase is large, the optimum phase change cannot be performed, and data cannot be transmitted / received correctly.

  The present invention relates to a resync apparatus used in a signal transmission system, and is characterized in that it has a function of discriminating whether a signal referred to when resync training is under the influence of large jitter or noise. The determination is made by examining the phase of the signal.

  In the present invention, when the signal is under the influence of large jitter or noise, the phase to be changed determined by performing resynchronization is ignored, or the previous phase change is compared with the phase obtained by investigation. The problem can be solved by calculating a probable phase from the direction.

  Further, the timing of investigating the phase of the signal used as a reference is changed to a short interval when the phase of the signal has changed as a result of sync training, and to a long interval when the phase has not changed. is there.

  According to the present invention, a resync apparatus used in a signal transmission system can correctly transmit and receive data even under the influence of noise and jitter when the operating frequency of the signal transmission system is increased.

  A resync apparatus that utilizes a noise determination apparatus that determines whether or not the phase determined by the resync training of the present invention is affected by noise or jitter. A specific embodiment thereof will be described below. To do.

(Embodiment 1)
FIG. 1 is a schematic diagram for explaining an example of an embodiment of a resync apparatus according to the present invention. Reference numerals 1 and 2 indicate independent apparatuses. DQS1 indicates an operation clock of the device 2, and DQ indicates a signal transmitted from the device 2 to the device 1.

  Reference numeral 101 denotes a phase determination device that determines the phase of the operation clock DQS1 from the system clock SCLK1 and the operation clock DQS1 of the device 1, and noise for determining whether the phase of the operation clock DQS1 is affected by noise or jitter. The determination unit 103 is notified.

  The noise determination unit 103 stores one or a plurality of phase signals of the operation clock DQS1 notified in the past, and determines whether the phase information Ph1 is affected by large jitter or noise based on the past history. The signal Ph2 indicating correct phase information is notified to the phase determination device 101. A method for determining whether or not the phase information Ph1 is affected by noise and a method for determining a correct phase signal will be described later.

  The phase determination device 101 notifies the phase change device 102 of the signal Ph2. The phase changing device 102 associates the operation clock DQS1 with a suitable phase of the system clock SCLK1 according to the signal Ph2, changes the phase of the signal DQ1, and outputs it as the signal SDQ1. Thus, even when the signal of the operation clock DQS1 is affected by noise, it is possible to change the phase correctly.

  Next, a method of determining whether or not the noise determination unit 103 has been affected by noise will be described below.

  The first determination method is a combination of the past phase information n times history and the latest phase information, and a majority decision is made. If the latest phase is the majority, there is no influence of the noise. It is a method of judging that there was an influence. This method is effective for sudden noise. Hereinafter, it is referred to as the majority method.

  The second determination method is as follows. In a signal transmission system, there is a tendency that the phase of a signal changes stepwise due to a change in system temperature. Therefore, in the second determination method, the direction of the phase change is calculated from the history of the past phase information, and the latest phase information changes by a certain amount to the same phase as the previous time or the calculated phase change direction. Indicates no influence of noise (the magnitude of the phase change that can be determined to be no influence of noise varies depending on the resolution of the phase that can be detected by the phase determination device), differs from the previous phase, and the calculated phase change direction and If there is a large change in the reverse direction or the calculated direction of phase change, it is determined that there is an influence of noise. Hereinafter, it is referred to as a phase change direction prediction method.

  FIG. 2 is a diagram for explaining the phase change direction prediction method. If a phase determination device with a resolution of every 90 degrees is used, the phase information to be notified when performing resync training is [00] (binary notation) between 0 and 90 degrees, and 90 to 180 degrees. [01] between degrees, [10] between 180 degrees and 270 degrees, and [11] between 270 degrees and 360 degrees.

  When the phase change as shown in FIG. 2 is performed, if the phase information of the latest operation clock DQS1 sent to the noise determination unit 103 is [01] and the previous operation clock DQS1 phase information is [00], the operation clock It can be predicted that the phase change of DQS1 exceeds 0 to 90 degrees and is directed to 180 degrees. In this case, when the phase information of the operation clock DQS1 to be notified next is [01] or [10], it can be determined that the direction of the change coincides with the prediction and thus it has not been affected by noise. On the other hand, if the phase information of the operation clock DQS1 is [00], [11], it is determined that the operation is affected by noise.

  This phase change direction prediction method is effective when applied when the temperature is rising or falling.

  When the noise determination unit 103 determines that there is no influence of noise, the signal Ph2 that the noise determination unit 103 notifies the phase determination device 101 has the same value as the phase information Ph1. On the other hand, when the noise determination unit determines that there is an influence of noise, the signal Ph2 to be notified to the phase determination device is determined by the following method.

  As method 1, the same value as the previously notified phase information is notified as information Ph2.

  In the method 2, when the phase change direction prediction method is used as a noise determination method, the signal Ph2 is determined by calculating from the previous phase information, the latest phase information, and the phase change direction. For example, when using the phase determination device of FIG. 2, the previous phase information is [00], the latest phase information is [10], and the direction of change exceeds 0 to 90 degrees, and is directed to 180 degrees. If [01] is calculated, the interval between [00] and [10] is complemented to calculate [01].

  Hereinafter, the operation of the resync apparatus when the majority voting method is used will be described with reference to the flowchart of FIG.

  After executing the restraining of step 101, the phase of the signal obtained by the restraining is stored as a history (step 102).

  In step 103, a majority vote with the previous history is taken, and in step 104, it is determined whether or not the player is a majority. If it is the majority, the phase to be changed is set in accordance with the phase of the signal obtained by the restraining this time (step 105). If it is the minority, the previous phase setting is continued ( Step 106).

  Next, the operation of the resync apparatus when the phase change prediction method is used will be described with reference to the flowchart of FIG.

  After executing resync training in step 201, the phase of the signal obtained by resync training is saved as a history (step 202).

  Next, in step 203, it is determined whether or not it is different from the previous phase, and if it is different from the previous transfer, it should be changed from the past history and the result of the present restraining using the above-described phase change prediction method. The phase is predicted, calculated, and set (step 204).

  If there is no difference from the previous phase in step 203, the previous setting is continuously used (step 205).

  Note that the noise determination unit 103 can consider both a case where the presence / absence of noise is determined by one method, and a case where there are a plurality of methods and the method to be applied is changed depending on the case.

  Note that the noise determination unit can be implemented either by hardware or by programmable software.

  As described above, in this embodiment, the noise determination unit 103 determines whether or not the phase of the operation clock DQS1 is affected by noise or jitter by using a plurality of determination methods. When it becomes high, even if the transmission signal is affected by noise and jitter, it is possible to transmit and receive correct data.

(Embodiment 2)
In (Embodiment 1), if the phase Ph1 obtained by resynchronization is different from the result of the previous restraining, it is considered that there is a factor that causes a significant change in the phase of the signal, so the time interval for performing restraining If the phase is narrowed and the phase is reliably determined, the safety is further improved. On the other hand, when the result of the resync train is always the same, the system is stable. In this case, it is more efficient to increase the time interval for performing the retraining so as not to put a burden on the system.

  An example in which such a function capable of operating the timing of performing restraining is added will be described as a second embodiment with reference to the drawings.

  FIG. 5 is a diagram in which a scheduling unit 104 is added to the resync apparatus according to (Embodiment 1). In the noise determination unit 103 according to the present embodiment, after determining the difference between the result of the previous restraining and the phase information Ph1 of the result of the current restraining, the signal s_ch is transmitted to the scheduling unit 104, and the apparatus 2 2 is an example of a resync apparatus having a function of notifying that the phase of the operation clock DQS1 from the phase change is in progress or has not changed.

  FIG. 6 shows a system for notifying the resync apparatus Re2 of the timing of performing retraining when the scheduling unit 104 of FIG. 5 receives s_ch that indicates that the operation clock DQS1 has changed.

  The resync apparatus Re2 performs resync training on the signal s_s2 transmitted from the apparatus S2, and performs settings for changing the signal s_s2 to the signal s_r2 that can be received by the apparatus R. The timing for performing restraining is when the scheduler SC transmits the signal sr_inst, and the timing for transmitting the signal sr_inst is determined by the signal s_ch2 transmitted from the resynchronizer Re2.

  When the signal s_ch2 indicates that the phase change has not occurred, the interval at which the signal sr_inst is transmitted from the scheduler SC is long. When the signal s_ch2 indicates that the phase change has occurred, the signal sr_inst from the scheduler SC So that the transmission interval of is shortened.

  Hereinafter, the operation of the resync apparatus Re will be described with reference to the flowchart of FIG.

  First, resync training is performed (step 301), and the phase information of the signal obtained as a result is stored as a history. Next, in step 303, it is determined whether or not there is a difference between the current phase and the previous phase. If there is a difference, in step 304, the waiting time until the next re-training is performed is set short.

  If there is no difference from the previous time, in step 305, a long waiting time until the next re-training is performed is set.

  In step 306, the controller waits for the set time, and then issues an instruction to perform resync training (step 307).

  Note that the scheduling unit can also be implemented by software operating on an external CPU (not shown).

The resync apparatus according to the present invention makes it possible to change the correct phase even when the resync training is performed when the signal phase is changed due to large jitter or noise in the signal transmission system. This can be realized by adding a few functions to the current resync device.
It is possible to cope with a signal transmission system with a higher operating frequency.

  The resync apparatus according to the present invention executes resync training at short intervals when a phase change occurs, reduces the possibility of erroneous phase change, improves the safety of the signal transmission system, When no change occurs, it can be executed at long intervals to reduce the load on the system. It is possible to improve system performance and reduce power consumption.

The figure which shows the structural example of the resync apparatus which is the 1st Embodiment of this invention The figure which shows the correspondence example of the phase and phase information of the phase change prediction method of the same device The figure which shows the operation flow when the majority decision method is used in the same device The figure which shows the operation flow when the phase change prediction method is used in the same device The figure which shows the structural example of the resync apparatus which is the 1st Embodiment of this invention Schematic diagram showing signal input and output of the device Diagram showing the operation flow of the device The figure which shows the outline of the conventional resync apparatus The figure which shows the phase change of the signal output with respect to the signal which the apparatus received

Explanation of symbols

DESCRIPTION OF SYMBOLS 101 Phase determination apparatus 102 Phase change apparatus 103 Noise determination part 104 Scheduling part

Claims (4)

A resync apparatus having a function for investigating the phase of the signal to determine whether or not the signal referred to is under the influence of noise when performing restraining. The apparatus according to claim 1, wherein when performing retraining, if the reference signal is found to be under the influence of noise, the obtained phase is ignored and the phase obtained by the previous resync training is obtained. A resync device having a function to prevent erroneous phase change by continuously using the. The apparatus according to claim 1, wherein when performing re-training, if the reference signal is found to be under the influence of noise, a phase change direction is predicted from the obtained phase and past history. , A resync device having a function of calculating and changing the phase. The timing of investigating the phase of the signal as a reference has a function of changing to a short interval when the phase of the signal has changed as a result of resync training, and to a long interval when the phase has not changed. The resync apparatus according to claim 3.

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