JP4338720B2 - Bit synchronization circuit - Google Patents

Description

  The present invention relates to a bit synchronization circuit used in high-speed serial communication technology and a semiconductor device incorporating the bit synchronization circuit.

  As is well known, in the high-speed serial communication technology, data is generally transmitted and received at a transmission and reception speed determined in advance by using a reference clock having the same frequency on the transmission side and the reception side. In order for the receiving side to correctly receive data sent from the transmitting side, the transmitting side and the receiving side need to operate in synchronization with each other. As one method, there is a method of supplying a clock signal for synchronizing with a data signal to the transmission side and the reception side. However, in recent high-speed serial communication of several hundred MHz to several tens GHz, waveform distortion, Because there are problems such as reflection, interference of cables and signals on the board, instead of sending the clock signal used for communication separately from the data signal, a redundant data bit is added to the data signal on the transmission side, and at a fixed time. Encoding is performed to ensure the transition of the data signal, and the data signal is transmitted. Usually, on the receiving side, since the data sent from the transmitting side includes timing information, the data is sampled, and after the sampling, extra bits are decoded.

  For example, in order to accurately receive NRZ (Non-Return to Zero) coded data on the transmission side, a synchronous clock for sampling data is generated for the data by using a bit synchronization circuit. There is a need to. For this reason, a circuit having a higher frequency than the communication speed is input to the bit synchronization circuit, and the circuit is usually configured so that a synchronization clock is generated so that the clock matches the center position of the data. In recent years, the communication speed of the serial communication interface has been increased from several hundred Mbps to several Gbps, and in order to realize high-speed and highly reliable communication, higher performance and higher reliability in relation to the bit synchronization circuit. Circuit is required.

  FIG. 10 shows a conventional bit synchronization circuit used in high-speed serial communication technology. In the bit synchronization circuit 100, the reference clock signal REFCLK is input together with the data input signal SDIN. In the phase comparison clock generation circuit 110, a bit operation clock signal (in FIG. 10) having a frequency corresponding to the communication speed is obtained from the reference clock signal REFCLK. And a total of eight clock signals CLK1 to CLK8 having different phases are generated based on the bit operation clock signal.

  FIG. 11 shows a timing chart of a reference clock signal, a bit operation clock signal, and a clock signal generated based on the bit operation clock signal. CLK1 to CLK8 each have a phase shifted by 1/8 cycle with respect to the adjacent clock signal. These clock signals CLK1 to CLK8 are respectively input to the input data edge detection unit 120 and the clock selection unit 140 via separate lines.

In the input data edge detection unit 120, the edge signals EDGE1 to EDGE8 are detected as a result of inputting the data input signal SDIN together with the clock signals CLK1 to CLK8 having different phases. These edge signals EDGE1 to EDGE8 are input to the clock determination unit 130. In the clock determination unit 130, the clock selection signal CKSL is generated from the edge position recognized based on the edge signals EDGE1 to EDGE8. The clock selection signal CKSL is input to the clock selection unit 140 together with the clock signals CLK1 to CLK8.
The clock selection unit 140 generates a write clock signal WRCK that is a data sampling clock signal for the buffer buffer 150 based on the input clock signals CLK1 to CLK8 and the clock selection signal CKSL.

  The buffer buffer 150 is a buffer composed of a single-bit flip-flop or a multi-bit FIFO, and is used to absorb a deviation or a clock jitter with respect to a frequency predetermined on the transmission side and the reception side. . In serial communication, an asynchronous FIFO having a 1-bit width and several bits to several tens of bits is generally used. The synchronized data SDOUT output from the buffer buffer 150 is read by subsequent circuits and processed as received data.

  FIG. 12 shows the configuration of the input data edge detection unit 120. The input data edge detection unit 120 includes data flip-flops (hereinafter referred to as flip-flops) 121a to 121h corresponding to eight clock signals CLK1 to CLK8 having different phases, and the same number of exclusive flip-flops 121a to 121h. OR gates 122a to 122h. Corresponding clock signals CLK1 to CLK8 and a serial data input signal SDIN are input to each of the flip-flops 121a to 121h. The output signals DFF1 to DFF8 from the flip-flops 121a to 121h are respectively input to two different EXOR gates. For example, the output of the flip-flop 121b is input to the EXOR gates 122a and 122b, the output of the flip-flop 121c is input to the EXOR gates 122c and 122b, and the output of the flip-flop 121h is output from the EXOR gates 122h and 122a. Is input.

  A signal output from each of the EXOR gates 122a to 122h becomes “HIGH” when the data input signal SDIN changes at the timing of the phase difference between the two input clock signals, and a signal indicating the edge position (hereinafter referred to as an edge signal). EDGE12, EDGE23, EDGE34, EDGE45, EDGE56, EDGE67, EDGE78, EDGE89. For example, the signal output from the EXOR gate 122a becomes “HIGH” level when the data input signal changes at the timing of the phase difference between CLK1 and CLK2. The edge signals EDGE12 to EDGE89 output from the EXOR gates 122a to 122h are supplied to the clock determination unit 130 via separate lines.

  In this example, the input data edge detection unit 120 uses eight lines for supplying clock signals having different phases. A method of performing edge detection with a clock having a higher frequency than the speed is also conceivable.

  FIG. 13 shows a timing chart of various signals related to the output timing of the clock signal WRCK for writing to the buffer buffer 150. As can be seen from FIG. 13, the first edge (rising edge) of the data input signal SDIN is located between the edge (rising edge) of the clock signal CLK1 and the edge (rising edge) of the clock signal CLK1, and the data input signal SDIN. Is located between the edge of the clock signal CLK2 (rising edge) and the edge of the clock signal CLK3 (rising edge), and the third edge of the data input signal SDIN is the clock signal CLKIN. It is located between the edge (rising edge) of the signal CLK3 and the edge (rising edge) of CLK4, and the last edge (falling edge) of the data input signal SDIN is the edge (rising edge) of the clock signal CLK2. It is located between the edge of CLK3 (rising edge).

  If an edge of the data input signal SDIN is detected, a detection pulse of a long period is output in the signals corresponding to the EDGE12 to EDGE89. Based on such a long detection pulse, the phase is delayed by about a half cycle with respect to EDGE 12, that is, CLK5 for sampling at the center of the input data, CLK6 for EDGE23, and further for EDGE34. CLK7 is output as a synchronization timing signal. If there is no edge transition in this synchronization timing signal and its cycle, the same clock as the previous cycle is output. Finally, a write clock signal WRCK output to the buffer buffer 150 is generated.

  The configuration after the input data edge detection unit 120 shown in FIG. 12, that is, the operation based on the timing of the clock determination unit 130 and the clock selection unit 140 is a known technique, and thus description thereof is omitted here.

  Next, a problem that may occur in the conventional bit synchronization circuit 100 will be described with reference to FIG. First, in order for the flip-flops 121a to 121h to operate normally, it is necessary to keep the input data constant for a certain period before and after the clock, but if the input data is not constant during this predetermined period, There is a possibility that the output signals DFF1 to DFF8 from the flip-flops 121a to 121h show unstable values other than 1 and 0, and such a phenomenon is called “metastability”. In FIG. 14, the output signal DFF2 from the flip-flop 121b is supposed to be “HIGH” level, but the transition of the data input signal SDIN is the setup hold of the flip-flop 121b. Since the timing requirement is not satisfied, the output signal DFF2 is in a metastable state with metastability. Here, as an example, a case where the output signal DFF2 in the metastable state is changing its output as shown by a bold solid line is shown.

  In addition, in the part to which the symbol B ″ shown in FIG. 14 is attached, the output signal DFF6 from the flip-flop 121f should be at the “LOW” level originally, but the data input to the flip-flop 121f is, for example, a semiconductor device Due to the manufacturing problem of the flip-flop 121f, the resistance value on the SDIN input side of the flip-flop 121f becomes abnormally high, or the signal line crosstalk related to the flip-flop 121f, the timing variation in manufacturing the semiconductor device, etc. Therefore, the output signal DFF6 is at the “HIGH” level.

  When a problem occurs in the output signal from the flip-flops indicated by the symbols A and B, the generation of the clock signal WRCK for writing to the buffer buffer 150 depends on the circuit configuration, but at the original timing. When data is not output and data is sampled in the buffer buffer 150, a timing error occurs and normal sampling cannot be performed, WRCK is not output and data is lost, WRCK occurs multiple times in one cycle, and data is extra Problems such as being taken in. In this case, the synchronization timing signal and the clock signal WRCK have a problem at the locations indicated by the symbols C ″ and D ″ shown in FIG. As a result, missing reception of serial data packet data, errors in received data, and the like occur, and normal reception cannot be performed.

  Generally, problems that reduce the reliability of the bit synchronization circuit include variations in characteristics due to manufacturing problems of flip-flops used in the input data edge detection unit in the bit synchronization circuit, and problems related to failure of the flip-flops. In addition, the above-mentioned metastability problem is known. Since metastability causes malfunction of the circuit, to improve the reliability of the circuit, it is necessary to reduce the probability of occurrence or to provide a bit synchronization circuit that does not cause malfunction even for metastability. It is.

  In addition, when a bit synchronization circuit is built in a semiconductor device, as a test method for judging the quality of the device, an LSI tester is usually used to add an input synchronized with a certain timing to the device, and an actual output If the expected value is measured and compared, and if an output value similar to the expected value is obtained, the device is determined to be a non-defective product. However, in a bit synchronous circuit that operates at high speed and asynchronously with serial data, it is necessary to prepare a number of asynchronous input patterns with respect to the system clock on the LSI tester. When testing with the expected value of the received data, the expected value cycle may be shifted due to the asynchronous input of the expected value of the received data even if it is a non-defective product. Furthermore, the method of deviation may vary from one device to another due to variations in the manufacturing of semiconductor devices. Therefore, in order to create a test program that can accurately determine the quality of a product, debugging the program (such as bugs) There is a problem that it takes a considerable amount of time for the removal operation. Conventionally, a technique capable of dealing with this problem has been demanded.

  Conventionally, the following bit synchronization circuits are known. For example, Japanese Patent No. 2595887 discloses a bit synchronization circuit that is configured completely digitally and can cope with high speed without using a counter. The use of a general clock multi-layer circuit or D flip-flop is similar to the present invention. However, since there is only one edge detection unit, the flip-flop in the bit synchronization circuit is in a metastable state. In some cases, there is a possibility of causing a malfunction in operation, and there is a problem of lack of reliability.

  Japanese Patent Application Laid-Open No. 9-36849 discloses a data sampling unit that samples an input signal to obtain an n-sequence signal, and a selection output unit that selects a signal synchronized with the received burst signal from the sampled n-sequence signal. And a bit synchronization circuit and a bit synchronization system that detect the rising and falling of a signal from a data sampling unit and can perform optimum sampling with respect to fluctuations in duty of input data. However, in this bit synchronization method, since both edges of the data change point are used, there is a problem that the sampling means does not follow at high speed. Also, since only one circuit is used for edge detection, if the flip-flop in the bit synchronization circuit is in a metastable state, there is a possibility of causing a malfunction in operation, which is not reliable. There's a problem.

Furthermore, JP-A-10-247903 discloses a high-speed burst signal in which received data is sporadically generated and input timing is indefinite, without using a high-speed clock exceeding the received data rate, and phase fluctuation A bit synchronization circuit having a good followability is disclosed. Since only one phase comparison circuit is used, there is a problem of lack of reliability.
Japanese Patent No. 2595887 JP-A-9-36849 JP-A-10-247903

  The present invention has been made in view of the above technical problem, and an object of the present invention is to provide a bit synchronization circuit that can cope with a high communication speed, has high reliability, and is easy to test.

The invention according to claim 1 of the present application is
In the bit synchronization circuit that synchronizes serial data with a clock signal when transmitting bit data,
Phase comparison clock generation means for generating a plurality of clock signals having different phases from a predetermined reference clock;
A plurality of clock signals generated by the phase comparison clock generation means are set for each group obtained by taking out every predetermined number, each of which detects an edge position from serial data, and generates a plurality of edge signals representing the edge position Edge detection means;
Based on the edge signals generated by the respective edge detecting means, a clock determining means for generating a plurality of synchronization timing signal corresponding to each of said plurality of edge detection means,
Clock selection means for selecting a write clock signal suitable for a clock signal for synchronizing serial data from the plurality of clock signals having different phases based on the synchronization timing signal generated by the clock determination means; And
(1) When a plurality of edge signals are output from each edge detection means, the clock selection means does not output a synchronization timing signal in that cycle,
(2) When a plurality of synchronization timing signals corresponding to each of the plurality of edge detection means are temporally continuous, the clock selection means causes the write clock signal to be written at the timing based on the continuous back signal. Is output .

  As is clear from the above description, according to the invention of claim 1 of the present application, a plurality of edge detection means are provided, and the operation of the edge detection means is confirmed based on the edge signal output from each edge detection means. Since the write clock signal suitable for the clock signal for synchronizing the serial data is generated, a highly reliable operation by the bit synchronization circuit can be realized.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Embodiment 1 FIG.
FIG. 1 is a block diagram of a serial transmission / reception apparatus including a bit synchronization circuit according to an embodiment of the present invention. This serial transmission / reception device 1 is incorporated in devices such as various computers, communication control devices, and terminals, and is a protocol layer 1 constituting an OSI (Open System Interconnection) reference model for interconnecting with other devices via a communication line. It is a physical layer that activates, maintains, and deactivates physical connections with other devices, and performs mechanical and electrical control for bit data transmission.

  When receiving data, serial data “Data +” and “Data−” are externally input to the bit synchronization circuit 10 via the receiver 2 included in the analog I / F unit 9, and the bit synchronization circuit 10 generates an internal clock. A sampling clock (also referred to as a synchronization timing signal) for sampling the data is generated based on the 1, 0 output from the receiver 2 with respect to the reference clock generated by the device 7 and the external oscillator 8, and the data is It is sampled and output to the receiving circuit 3 as serial data. The receiving circuit 3 performs data decoding processing according to the coding used in communication, and the interface unit 4 performs an operation of outputting the data as parallel data “DATA” inside the device.

  On the other hand, at the time of data transmission, parallel data supplied from the inside of the device is converted into serial data in the interface unit 4, code processing is executed by the transmission circuit 5, and serial processing is performed via the driver 6 included in the analog I / F unit 9. Output to the outside as data.

  FIG. 2 shows the configuration of the bit synchronization circuit 10. The bit synchronization circuit 10 includes a phase comparison clock generation circuit 20, first and second input data edge detection units 30 and 40, a clock determination unit 50, a clock selection unit 60, and a buffer buffer 70. The synchronization timing signal is sampled from the data input signal SDIN using the reference clock REFCLK generated by the internal clock generator 7 and the external oscillator 8 (see FIG. 1), and synchronization is performed based on the synchronization timing signal. Output serial data. The basic configuration and operation of the bit synchronization circuit 10 are the same as those described with reference to FIG. 10 as the prior art. In the present invention, the signal is used when sampling the synchronization timing signal from the data input signal SDIN. As a means for detecting the edge position, a plurality (two in this embodiment) of input data edge detectors 30 and 40 are provided so that they provide a bit synchronization circuit that is faster and more reliable. Operate.

  In the bit synchronization circuit 10, first, in the phase comparison clock generation circuit 20, a bit operation clock signal having a frequency corresponding to the communication speed is generated from the reference clock signal REFCLK. Eight clock signals CLK1 to CLK8 are generated. Here, the timing chart of the reference clock signal REFCLK, the bit operation clock signal BTCLK, and the clock signals CLK1 to CLK8 generated based on the bit operation clock signal is the same as that illustrated in the description of the prior art. Each of CLK8 has a phase shifted by 1/8 cycle with respect to the adjacent clock signal (see FIG. 11).

  As in the prior art, these clock signals CLK1 to CLK8 are each output from the phase comparison clock generation circuit 20 via separate lines. In this embodiment, the first and second input data edge detections are performed. As the units 30 and 40 are provided, the clock signals CLK1 to CLK8 are divided into two groups corresponding to the edge detection units 30 and 40 and output. More specifically, each group is formed by picking up every other clock signal having a phase shifted by 1/8 cycle in order from CLK1 to CLK8, and odd clock signals CLK1, CLK3, CLK5, CLK7 are The even numbered clock signals CLK2, CLK4, CLK6, and CLK8 are input to the second input data edge detecting unit 40.

  FIG. 3 shows the configuration of the first and second input data edge detection units 30 and 40. First, the first input data edge detection unit 30 includes four flip-flops 31a, 31b, 31c, and 31d corresponding to the clock signals CLK1, CLK3, CLK5, and CLK7, and four EXOR gates 32a, 32b, 32c, and 32d, respectively. have. A data input signal SDIN is input to each of the flip-flops 31a to 31c together with a corresponding clock signal, and the output signals DFF1, DFF3, DFF5, and DFF7 from each of the flip-flops 31a to 31d are respectively connected to two different EXOR gates. Entered. That is, the output signal DFF1 from the flip-flop 31a is output to the EXOR gates 32a and 32d, the output signal DFF3 from the flip-flop 31b is output to the EXOR gates 32a and 32b, and the output signal DFF5 from the flip-flop 31c is Further, the output signal DFF7 from the flip-flop 31d is inputted to the EXOR gates 32c and 32d. In the first input data edge detecting unit 30, edge signals EDGE13, EDGE35, EDGE57, and EDGE79 representing edge positions are output from any one of the EXOR gates 32a, 32b, 32c, and 32d.

  On the other hand, the second input data edge detection unit 40 includes four flip-flops 41a, 41b, 41c, and 41d corresponding to the clock signals CLK2, CLK4, CLK6, and CLK8, and four EXOR gates 42a, 42b, and 42c. , 42d. Similarly to the first input data edge detection unit 30, the data input signal SDIN is input to each of the flip-flops 41a to 41c together with the corresponding clock signal, and the output signals DFF2, DFF4, and DFF6 from the flip-flops 41a to 41d are input. , DFF8 are respectively input to two different EXOR gates. That is, the output signal DFF2 from the flip-flop 41a is sent to the EXOR gates 42a and 42d, the output signal DFF4 from the flip-flop 41b is sent to the EXOR gates 42a and 42b, and the output signal DFF6 from the flip-flop 41c is Further, the output signal DFF8 from the flip-flop 41d is input to the EXOR gates 42c and 42d. In the second input data edge detection unit 40, edge signals EDGE24, EDGE46, EDGE68, and EDGE80 representing edge positions are output from any one of the EXOR gates 42a, 42b, 42c, and 42d.

  In the clock determination unit 50, first and second synchronization timing signals are generated based on the edge signals sent from the first and second input data edge detection units 30 and 40, respectively. . These first and second synchronization timing signals are sent to the clock selection unit 60 and used by the clock selection unit 60 as clock selection signals.

  The operation of the bit synchronization circuit 10 under the same conditions as those described with reference to FIG. 12 for the prior art will be described with reference to FIG. FIG. 4 is a timing chart of various signals in the bit synchronization circuit 10. In the bit synchronization circuit 10, when each synchronization timing signal and the clock signal WRCK for writing to the buffer buffer 70 generated from the synchronization timing signal are output, synchronization is performed according to the algorithm defined in the following (1) to (4). Assume that a timing signal is generated.

(1) When a plurality of edge signals are output from the input data edge detection units 30 and 40, the synchronization timing signal in that cycle is not output.

(2) When the first and second synchronization timing signals are temporally continuous, the write clock signal WRCK to the buffer buffer 70 is output at a timing based on the continuous rear signal.

(3) When the first and second synchronization timing signals are not continuous in time, the same write clock signal WRCK as the previous cycle is output.

(4) When only one of the first and second synchronization timing signals is generated, the same write clock signal WRCK as the previous cycle is output.

  At this time, if at least the algorithms (1) and (2) among the algorithms (1) to (4) are realized by circuit design, the parts marked with the symbols A and B shown in FIG. Even when there is such an error, the write clock signal WRCK to the buffer buffer 70 is normally output. The algorithms (3) and (4) specify that when an error in the bit synchronization circuit 10 is detected, a clock signal WRCK for writing having the same phase as that of the previous cycle, which is the safest, is output. To do.

  Thus, the bit synchronization circuit 10 is equipped with a plurality of input data edge detection units 30 and 40, and a plurality of synchronization timing signals are generated based on the edge signals from the respective edge detection units. Based on the above, the generation of the write clock signal WRCK makes it possible to maintain normal reception of serial data, and to improve reliability.

  In addition, about the algorithm prescribed | regulated to said (1)-(4), in this embodiment, it is an illustration thing and it is not limited to this. Further, the number of input data edge detection units is not limited to two. For example, the phase of the write clock signal WRCK is determined by majority from each edge detection unit using three input data edge detection units. You may make it produce | generate.

  Further, in the bit synchronization circuit 10 shown in FIG. 2, a buffer buffer is used by using a plurality of synchronization timing signals generated based on edge signals output from the plurality of first and second input data edge detection units 30 and 40. A data sampling clock for 70 is generated, and a signal indicating an error state is generated using an edge signal from the input data edge detection unit. For example, when there are a plurality of edge signals in each input data edge detection unit, when the synchronization timing signals of the two input data edge detection units are not continuous, the error state is one of the first and second synchronization timing signals. In this bit synchronization circuit 10, a signal representing such an error state is output from the clock determination unit 50 as an error status signal of the bit synchronization circuit 10.

  As shown in FIG. 1, when the bit synchronization circuit 10 is built in the serial transmission / reception device 1, the bit synchronization circuit 10 operates at a very high speed and operates completely asynchronously. Although there was a problem that it was difficult, by using the error status signal output from the clock determination unit 50, it is possible to test with one kind of expected value program that has no error for all asynchronous patterns Thus, the device 1 can be easily tested.

  In addition, when selecting using the expected value of the received data, a defect cannot be detected until the reception is completed, but the error status signal of the bit synchronization circuit existing at the position of receiving and receiving the serial data as in the patent of the present application. When the semiconductor device is tested using this, the error detection timing is earlier than when the expected value of the received data that is known at the end of reception is used, thereby enabling the defective product to be found early.

  Next, FIG. 5 shows a configuration corresponding to the second input data edge detection unit 40 included in the clock determination unit 50. FIG. 6 shows a timing chart of various signals related to this configuration. The symbols attached to the signal waveforms shown in FIG. 6 correspond to the input and output signals in FIG. Although not shown in FIG. 2 showing the overall configuration of the bit synchronization circuit 10, the clock determination unit 50 includes a phase comparison clock generation circuit together with edge signals from the first and second input data edge detection units 30 and 40. The clock signal from 20 is input. The clock determination unit 50 includes flip-flops 51a, 51b, 51c, and 51d, AND gates 52a, 52b, 52c, and 52d, flip-flops 53a, 53b, 53c, and 53d, and AND gates 54a, 54a, 54b, 54c, and 54d. And the OR gate 55, the clock signals CLK 2, CLK 4, CLK 6, CLK 8 from the phase comparison clock generation circuit 20 and the edge signals EDGE 24, EDGE 46, EDGE 68, EDGE 80 from the second input data edge detector 40. And configured to generate a second synchronization timing signal.

  Although not particularly illustrated, the configuration corresponding to the first input data edge detection unit 30 in the clock determination unit 50 includes the clock signals CLK1, CLK3, CLK5, CLK7 from the phase comparison clock generation circuit 20 and the first input data edge. Using the edge signals EDGE13, EDGE35, EDGE57, and EDGE79 from the detection unit 30, the same operation as the configuration corresponding to the second input data edge detection unit 40 is performed to generate the first synchronization timing signal.

Hereinafter, another embodiment of the present invention will be described. In the following, the same components as those in the first embodiment are denoted by the same reference numerals, and further description thereof is omitted.
Embodiment 2. FIG.
FIG. 7 is a diagram showing an arrangement of each component of the input data edge detection unit according to the second embodiment of the present invention. Normally, when detecting an edge signal as described above, it is necessary for the flip chip to operate as intended in the design. For this purpose, the data input signal SDIN and the clock signals CLK1 to CLK8 are input to the flip chip. On the other hand, particularly accurate timing is required. The first and second input data edge detection units 30 ′ and 40 ′ have circuit structures substantially equivalent to the input data edge detection units 30 and 40 shown in FIG. 3, respectively, that is, each of the flip chip 31a. To 31d and EXOR gates 32a to 32d, flip-chips 41a to 41d and EXOR gates 42a to 42d. In the second embodiment, each of these components is provided when mounted in the serial transmission / reception device 1. Are arranged symmetrically with respect to the input terminals of the clock signal and the data input signal. According to such an arrangement structure, a clock signal and a data input signal are input at a timing closer to each component at the same time, and each flip chip can be operated at a substantially uniform timing.

Embodiment 3 FIG.
FIG. 8 is a diagram showing an arrangement of each component of the input data edge detection unit according to the third embodiment of the present invention. In the second embodiment, the configurations (particularly flip-flops) of the first and second input data edge detection units are arranged symmetrically with respect to the input terminals of the clock signal and the data input signal. In the third embodiment, in order to realize signal input at a more accurate timing, each configuration of the first and second input data edge detection units 30 ″ and 40 ″ is provided as an input terminal for a clock signal and a data input signal. On the other hand, they are arranged symmetrically in the vertical and horizontal directions.

  As in the second and third embodiments, each input data edge detection unit is arranged vertically or laterally symmetrically with respect to each signal input terminal, thereby enabling signal input at the required accurate timing. This can improve the operational reliability of the bit synchronization circuit.

Embodiment 4 FIG.
FIG. 9 is a diagram showing an arrangement of each component of the input data edge detection unit according to the fourth embodiment of the present invention. As in the above-described embodiment, a plurality of (first and second) input data edge detection units 80 and 90 are provided. In the fourth embodiment, each input data edge detection unit 80 and 90 includes: Each is composed of eight flip chips 81a to 81h and 91a to 91h and eight EXOR gates 82a to 82h and 92a to 92h. Further, each configuration is arranged symmetrically with respect to the input terminals of the data input signal SDIN and the clock signals CLK0 to CLK9 and A to F.

  When the first and second input data edge detectors 80 and 90 are employed, the clock signals CLK0 to CLK9, A whose phases are shifted by 1/16 cycle in the bit synchronization circuit are not shown. It is necessary to use a phase comparison clock generation circuit capable of outputting ~ F.

  In the fourth embodiment, each input data edge detection unit is composed of eight flip chips and EXOR gates, and a clock signal having a smaller phase difference is used, so that the detection resolution for the edge signal can be improved. Further, in the fourth embodiment, each configuration of the input data edge detection unit is arranged symmetrically with respect to the input terminal of each signal, so that it is required as in the second and third embodiments. Thus, it is possible to realize signal input at an accurate timing and to improve the operation reliability of the bit synchronization circuit.

  Note that the present invention is not limited to the illustrated embodiments, and it goes without saying that various improvements and design changes are possible without departing from the scope of the present invention. For example, the configuration of the input data edge detection unit is not limited to four or eight flip-flops and EXOR gates, and for example, 16 flip-flops and EXOR gates may be used.

1 is a block diagram of a serial transmission / reception device including a bit synchronization circuit according to an embodiment of the present invention. It is a block diagram which shows the said bit synchronization circuit. It is a figure which shows the structure of the input data edge detection part contained in the said bit synchronous circuit. 4 is a timing chart of various signals in the bit synchronization circuit. It is a figure which shows the structure of the clock determination part contained in the said bit synchronous circuit. 6 is a timing chart of various signals related to the clock selection unit. It is a figure which shows arrangement | positioning of each structure of the input data edge detection part which concerns on Embodiment 2 of this invention. It is a figure which shows arrangement | positioning of each structure of the input data edge detection part which concerns on Embodiment 3 of this invention. It is a figure which shows arrangement | positioning of each structure of the input data edge detection part which concerns on Embodiment 4 of this invention. It is a block diagram which shows the conventional bit synchronous circuit. It is a timing chart of various signals related to a phase comparison clock generation circuit included in a conventional bit synchronization circuit. It is a figure which shows the structure of the input data edge detection part contained in the conventional bit synchronous circuit. It is a normal timing chart of various signals related to a conventional bit synchronization circuit. It is a timing chart with a problem of various signals related to the conventional bit synchronization circuit.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Serial transmission / reception apparatus 10 ... Bit synchronous circuit 20 ... Phase comparison clock generation circuit 30 ... 1st input data edge detection part 40 ... 2nd input data edge detection part 50 ... Clock determination part 60 ... Clock selection part 70 ... Buffer buffer

Claims (3)

In the bit synchronization circuit that synchronizes serial data with a clock signal when transmitting bit data,
Phase comparison clock generation means for generating a plurality of clock signals having different phases from a predetermined reference clock;
A plurality of clock signals generated by the phase comparison clock generation means are set for each group obtained by taking out every predetermined number, each of which detects an edge position from serial data, and generates a plurality of edge signals representing the edge position Edge detection means;
Based on the edge signals generated by the respective edge detecting means, a clock determining means for generating a plurality of synchronization timing signal corresponding to each of said plurality of edge detection means,
Clock selection means for selecting a write clock signal suitable for a clock signal for synchronizing serial data from the plurality of clock signals having different phases based on the synchronization timing signal generated by the clock determination means; And
(1) When a plurality of edge signals are output from each edge detection means, the clock selection means does not output a synchronization timing signal in that cycle,
(2) When a plurality of synchronization timing signals corresponding to each of the plurality of edge detection means are temporally continuous, the clock selection means causes the write clock signal to be written at the timing based on the continuous back signal. bit synchronization circuit according to claim <br/> be output. In the bit synchronization circuit that synchronizes serial data with a clock signal when transmitting bit data,
Phase comparison clock generation means for generating a plurality of clock signals having different phases from a predetermined reference clock;
The clock signals generated by the phase comparison clock generating means are set for every two groups obtained by taking out every predetermined number, detect edge positions from serial data, and generate edge signals representing the edge positions, respectively. First and second edge detection means;
Clock determining means for generating first and second synchronization timing signals corresponding to the first and second edge detecting means based on the edge signals generated by the edge detecting means;
Clock selection means for selecting a write clock signal suitable for a clock signal for synchronizing serial data from the plurality of clock signals having different phases based on the synchronization timing signal generated by the clock determination means; And
(1) When a plurality of edge signals are output from each edge detection means, the clock selection means does not output a synchronization timing signal in that cycle,
(2) When the first and second synchronization timing signals are temporally continuous, the clock selection means outputs the write clock signal at the timing of the continuous rear signal.
A bit synchronization circuit characterized by the above .   In the bit synchronization circuit that synchronizes serial data with a clock signal when transmitting bit data,
  Phase comparison clock generation means for generating a plurality of clock signals having different phases from a predetermined reference clock;
  The clock signals generated by the phase comparison clock generating means are set for every two groups obtained by taking out every predetermined number, detect edge positions from serial data, and generate edge signals representing the edge positions, respectively. First and second edge detection means;
  Clock determining means for generating first and second synchronization timing signals corresponding to the first and second edge detecting means based on the edge signals generated by the edge detecting means;
  Clock selection means for selecting a write clock signal suitable for a clock signal for synchronizing serial data from the plurality of clock signals having different phases based on the synchronization timing signal generated by the clock determination means; And
(1) When a plurality of edge signals are output from each edge detection means, the clock selection means does not output a synchronization timing signal in that cycle,
(2) When the first and second synchronization timing signals are temporally continuous, the clock selection means outputs the write clock signal at the timing of the continuous rear side signal,
(3) If the first and second synchronization timing signals are not continuous in time, the clock selection means outputs the same write clock signal as the previous cycle,
(4) When only one of the first and second synchronization timing signals is generated, the clock selection means outputs the same write clock signal as the previous cycle.
A bit synchronization circuit characterized by the above.

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