CN106550289B - Method, device and client for providing reference clock for serial-parallel converter - Google Patents
Method, device and client for providing reference clock for serial-parallel converter Download PDFInfo
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- CN106550289B CN106550289B CN201510595446.8A CN201510595446A CN106550289B CN 106550289 B CN106550289 B CN 106550289B CN 201510595446 A CN201510595446 A CN 201510595446A CN 106550289 B CN106550289 B CN 106550289B
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- H04L1/00—Arrangements for detecting or preventing errors in the information received
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Abstract
The embodiment of the invention discloses a method for providing a reference clock for a serial-parallel converter, which comprises the following steps: recovering a service clock from service clock information of the optical transmission frame; and generating reference clocks of a transmitting side and a receiving side of the serial-parallel converter by using the recovered service clock. The embodiment of the invention also discloses a device for providing the reference clock for the serial-parallel converter and a client.
Description
Technical Field
The present invention relates to clock management technology in optical transmission networks, and in particular, to a method, an apparatus, and a client for providing a reference clock for a serial-to-parallel converter.
Background
In the field of Optical Transport networks, as an Optical Transport network gradually becomes a next generation backbone Transport network, various different types of customer services are encapsulated in an Optical Channel Transport Unit (OTU) and then transmitted through the Optical Transport network, such as: ethernet traffic with different rates, Fibre Channel (FC) traffic, Synchronous Transport Mode (STM) traffic, etc.
In order to ensure that various service data can be transmitted to the client without loss, clock information needs to be extracted from the encapsulated OTU frame, and then the client service clock is recovered through a clock recovery technology. However, in the prior art, there are few technical solutions suitable for OTN clock recovery, and the proposed technical solutions have severe hysteresis, have certain requirements on interfaces, and require additional clock modules, thereby increasing the design cost.
Disclosure of Invention
In view of this, in order to solve the problems in the prior art, embodiments of the present invention are to provide a method, an apparatus, and a client for providing a reference clock for a serial-to-parallel converter, which can timely and accurately recover a service clock, and are simple to operate and low in design cost.
The technical scheme of the embodiment of the invention is realized as follows:
the embodiment of the invention provides a method for providing a reference clock for a serial-parallel converter, which comprises the following steps:
recovering a service clock from service clock information of the optical transmission frame;
and generating reference clocks of a transmitting side and a receiving side of the serial-parallel converter by using the recovered service clock.
In the above scheme, the method further comprises:
generating a backup clock; completing the switching between the backup clock and the recovered service clock;
the generating reference clocks of a transmitting side and a receiving side of a serial-parallel converter by using the recovered service clock comprises:
and generating reference clocks of the transmitting side and the receiving side of the serial-parallel converter by utilizing the switching between the recovered service clock and the backup clock.
In the above scheme, the generating the backup clock is: generating a backup clock by adopting self-oscillation;
the method for generating the backup clock by adopting the self-oscillation comprises the following steps: configuring a self-oscillation clock parameter according to the service clock information of the optical transmission frame, generating self-oscillation clock gap information, and dividing the frequency of the self-oscillation clock gap information to obtain the backup clock;
and generating an alarm signal, and switching the backup clock and the service clock according to a switching instruction generated by the alarm signal.
In the foregoing solution, the completing the switching between the backup clock and the service clock further includes: prolonging the alarm signal;
the switching instruction generated according to the alarm signal comprises: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction;
the priority order of the switching instructions is as follows: and a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction.
In the foregoing solution, the recovering the service clock from the service clock information of the optical transmission frame includes:
extracting information of a service clock from an optical transmission frame to generate gap information of the service clock;
correcting the generated service clock gap information;
and processing the corrected service clock gap information to recover the service clock.
The embodiment of the invention also provides a device for providing a reference clock for a serial-parallel converter, which comprises:
a clock recovery unit, configured to recover a service clock from service clock information of an optical transmission frame;
and the reference clock generating unit is used for generating reference clocks of a transmitting side and a receiving side of the serial-parallel converter by using the recovered service clock.
In the above solution, the reference clock generating unit is further configured to generate a backup clock; completing the switching between the backup clock and the recovered service clock;
the reference clock generating unit generates reference clocks of a transmitting side and a receiving side of the serial-parallel converter by using the recovered service clock, and comprises: and generating reference clocks of the transmitting side and the receiving side of the serial-parallel converter by utilizing the switching between the recovered service clock and the backup clock.
In the above scheme, the reference clock generating unit is specifically configured to generate a backup clock by using a self-oscillation;
the reference clock generating unit generates the backup clock by adopting the self-oscillation, and comprises the following steps: configuring a self-oscillation clock parameter according to the service clock information of the optical transmission frame, generating self-oscillation clock gap information, and dividing the frequency of the self-oscillation clock gap information to obtain the backup clock; and generating an alarm signal, and switching the backup clock and the service clock according to a switching instruction generated by the alarm signal.
In the above scheme, the reference clock generating unit is further configured to extend an alarm signal;
the switching instruction generated according to the alarm signal comprises: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction;
the priority order of the switching instructions is as follows: and a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction.
In the above scheme, the clock recovery unit is specifically configured to extract information of a service clock from an optical transmission frame, and generate gap information of the service clock; correcting the generated service clock gap information; and processing the corrected service clock gap information to recover the service clock.
An embodiment of the present invention further provides a client for providing a reference clock for a serial-to-parallel converter, including: any of the above apparatus for providing a reference clock for a serial to parallel converter.
The method, the device and the client for providing the reference clock for the serial-parallel converter provided by the embodiment of the invention recover the service clock from the service clock information of the optical transmission frame; generating reference clocks of a transmitting side and a receiving side of a serial-parallel converter by using the recovered service clock; furthermore, the embodiment of the present invention may combine the switching between the backup clock and the recovered service clock, so that a common reference clock can be provided for the transmitting side and the receiving side of the serial-parallel converter, and on the basis of saving design cost, the situation that the receiving side cannot normally operate due to the abnormal operation of the service clock recovered by the transmitting side when the transmitting side and the receiving side of the serial-parallel converter share one reference clock can be effectively avoided.
Drawings
Fig. 1 is a schematic flow chart of an implementation of a method for providing a reference clock for a serial-to-parallel converter according to an embodiment of the present invention;
FIG. 2 is a schematic structural diagram of an apparatus for providing a reference clock for a serial-to-parallel converter according to an embodiment of the present invention;
FIG. 3 is a block diagram of an apparatus for providing a reference clock to a serial-to-parallel converter according to a preferred embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and examples.
Fig. 1 is a schematic implementation flow diagram of a method for providing a reference clock for a serial-to-parallel converter according to an embodiment of the present invention, and as shown in fig. 1, a method for providing a reference clock for a serial-to-parallel converter according to an embodiment of the present invention includes:
step 101, recovering a service clock from service clock information of an optical transmission frame;
specifically, the recovering the service clock from the service clock information of the optical transmission frame includes: extracting information of a service clock from an optical transmission frame to generate gap information of the service clock; correcting the generated service clock gap information; and processing the corrected service clock gap information to recover the service clock.
Here, the service clock information may include: the number of bits in a frame and the number of system clocks in an optical transmission frame.
And 102, generating reference clocks of a transmitting side and a receiving side of the serial-parallel converter by using the recovered service clock.
Before this step, the method further comprises: generating a backup clock; and switching between the backup clock and the recovered service clock is completed.
Correspondingly, the step of generating reference clocks at the transmitting side and the receiving side of the serial-to-parallel converter by using the recovered service clock includes: and generating reference clocks of the transmitting side and the receiving side of the serial-parallel converter by utilizing the switching between the recovered service clock and the backup clock.
The generated backup clock can be generated according to the service clock information of the optical transmission frame; the method for generating the backup clock may be as follows: generating a backup clock by adopting self-oscillation;
specifically, the generating the backup clock by using the natural vibration includes: configuring a self-oscillation clock parameter according to the service clock information of the optical transmission frame, generating self-oscillation clock gap information, and dividing the frequency of the self-oscillation clock gap information to obtain the backup clock; and generating an alarm signal, and switching the backup clock and the service clock according to a switching instruction generated by the alarm signal. Wherein the alert signal may be generated from a client.
Here, the service clock information of the optical transmission frame may include: the number of bits in a frame and the number of system clocks in an optical transmission frame.
Accordingly, the generating the backup clock using the natural vibration may include: firstly, two parameters of a self-oscillation clock are configured, a self-oscillation clock notch is output according to a sigma-delta algorithm, frequency division is carried out on the clock notch generated by the self-oscillation, and the frequency-divided clock is a backup clock.
Here, the completing the switching between the backup clock and the service clock further includes: prolonging the alarm signal; seamless switching between the service clock and the backup clock can be realized through prolonging the alarm signal.
The switching instruction generated according to the alarm signal comprises: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction; wherein, the priority order of the switching instruction is: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction; here, the frequency offset switching instruction refers to a frequency offset switching instruction for switching to the backup clock, and may be generated when a frequency offset value of the service clock obtained by sampling is greater than configured maximum and minimum frequency offset values by sampling the recovered service clock.
The following describes the handover with the alarm signal extension command and the forced handover command, the handover including: sampling an input client alarm signal, judging whether the sampled alarm signal is effective or not, generating a pulse in the process of the alarm signal from effective to ineffective after the alarm signal is effective, starting a counter, resetting when the counter counts to a configuration value, and waiting for the pulse to trigger the counter again; when the counter is smaller than the configuration value, the output alarm signal is forced to be effective; when the value is larger than or equal to the configuration value, the alarm signal is output as input. The prolonged alarm signal is a switching signal of the clock, and the clock can be switched from the service clock to the backup clock according to the forced effective alarm signal and the prolonged alarm signal; switching from said backup clock to said service clock after said alert signal transitions from active to inactive.
When the method provided by the embodiment of the invention is applied to the client, the signal can be configured through the CPU of the client, and the clock is forcibly switched.
The method for providing the reference clock for the serial-parallel converter provided by the embodiment of the invention is based on the idea that the service clock recovered from the optical transmission frame is taken as the reference clock of the transmitting side and the receiving side of the serial-parallel converter as a main design idea, and the switching between the backup clock and the service clock is combined, so that not only can the common reference clock be provided for the transmitting side and the receiving side, the design cost is saved, but also the situation that the receiving side cannot normally work due to the fact that the service clock recovered by the transmitting side cannot normally work when the transmitting side and the receiving side share one reference clock can be effectively avoided.
A preferred embodiment of the present invention provides a method for providing a reference clock for a serial-to-parallel converter, the method specifically includes:
step a1, extracting clock valid information of the client service from the OTU frame, where the valid information includes: the number Cm of the M blocks of the effective payload and the bit remainder sigma Cnd value of the M blocks; from these 2 values, the number Cn of bits in one frame is calculated, and the number CNT of system clocks in one frame is counted, and the time when these pieces of information are all prepared is denoted as point a.
And step A2, performing sigma-delta operation on the bit number Cn and the clock number CNT, and outputting a clock gap signal of the customer service.
If Cn + Cn _ RM > is equal to CNT, the output clock gap is valid, and the difference between Cn + Cn _ RM and CNT is stored in the memory cell storing the value of Cn _ RM.
Cn + CN _ RM < CNT, the output clock gap is invalid, and the value of Cn + CN _ RM is stored in a storage unit storing the value of CN _ RM.
The value of CN _ RM is the value in the storage unit.
Step A3, while step a2 is running, starts a counter S _ CNT, and when S _ CNT > equals to the value of CNT, the counter S _ CNT is set to 1 to count again, which indicates that the comparison operation of step a2 is completed and also indicates that the sample point a is ready for the values of Cn and CNT, and this time is denoted as point B.
Step A4, starting a counter AB _ CNT, calculating the number of clocks between the point A and the point B, if the value of AB _ CNT is less than a certain value, there will be the situation that the point B is ready and the point A is not ready clock information, because the service rate has jitter, at this time, the last clock information will be used again to continue the operation, and the repeated operation will cause the recovery error of the service clock rate. If the situation occurs, half of the Cn and CNT values in the step A1 are taken at the point B time to carry out the sigma-delta operation in the step A2, and the distance between the point A and the point B is separated after the sigma-delta operation, so that the recovery error is effectively prevented.
Here, the specific value is determined according to conditions such as a rate and a bit width of the service, and is determined according to an actual situation.
The above steps a1 to a4 are processing flows of the client clock information extraction module, and can output a uniform clock gap, for client services without rate change, the client services without rate change can be directly sent to the clock recovery channel, and the client service clock rate needs to be recovered again at the gap after the services with rate change, and the services with rate change, which are coded or encapsulated. The rate recovery process is similar to steps a1 through a4 described above.
And step A5, inputting the recovered clock gap information to a gap conversion module, and adjusting the recovered service clock. Firstly, judging whether the interface FIFO waterline is in a position which is too low or too high according to the monitored interface FIFO waterline. For the position that the FIFO waterline is too high, in the configured adjustment time, an effective signal is added in the input gap, the recovered clock is accelerated, the FIFO waterline is descended, and the adjustment is stopped after the FIFO waterline is descended to a reasonable position. And for the FIFO waterline at the too low position, deleting an effective signal in the input gap within the configured adjustment time, slowing down the recovered clock, enabling the FIFO waterline to start rising, and stopping adjustment after the FIFO waterline rises to a reasonable position. The process needs reasonable configuration and adjustment time, so that the adjusted clock frequency offset meets the requirements.
Step a6, according to the requirement of the customer service clock, the bit width of the adjusted clock gap can be converted and smoothed. If the bit width of the input clock gap is nbit and needs to be converted into mbit, the configuration values are one multiple of m and one multiple of n. Generating two counters M _ CNT and MS _ CNT, counting the number of clock gaps input by the counter M _ CNT, and setting the counter M _ CNT to be 1 for counting again when the counted value is more than or equal to multiple of M. And counting the number of clocks by the counter MS _ CNT, outputting a counting value MS _ VAL by the counter MS _ CNT when the M _ CNT is more than or equal to a multiple of M, and setting the counter MS _ CNT to be 1 for counting again.
Step A7, after sigma-delta operation is carried out on the configured value which is the multiple of n in step A6 and the statistic value MS _ VAL, the output is the converted clock gap. It is also necessary to prevent conversion errors during conversion by monitoring at A, B in the previous step.
Step A8, configuring a frequency division parameter N1, starting a counter N _ CNT, counting the input clock notch, when the count value of the counter N _ CNT is greater than or equal to N1, negating the output signal, and when the count value is less than N1, keeping the output signal unchanged, completing the frequency division of the clock notch by 2 x N1, wherein the frequency-divided clock is a recovered smooth clock.
The above steps a5 to A8 complete the conversion and frequency division of the clock notch, and output the smooth clock required by the customer service.
The serial-parallel converter transmission side and the receiving side need to use two reference clocks to enable the serial-parallel converter to work, and generally, clock recovery is realized on the serial-parallel converter transmission side. However, when the OTN service is abnormal or the data recovery is incorrect, the service clock cannot be recovered, and thus the receiving side cannot work due to the common reference clock, which is not allowed, in this embodiment of the present invention, a self-oscillation generation backup clock and a clock switching function are used to solve the problem.
And step A9, configuring two parameters of the self-oscillation clock, performing sigma-delta operation in the processing of the step A2, outputting a clock notch of the self-oscillation, configuring a frequency division parameter n2, and performing frequency division on the clock notch generated by the self-oscillation by 2 x n2, wherein the frequency-divided clock is a backup clock.
When the alarm signal is effective to ineffective, the data can not immediately recover to be normal, and can normally work after a period of time, so that the alarm signal is prolonged to realize seamless switching between clocks.
Step A10, sampling the input client alarm signal, judging whether the sampled alarm signal is valid, when the alarm signal is valid, using the backup clock as the reference clock of the serial-parallel converter, when the alarm signal is valid to invalid, generating a pulse, starting a counter SSF _ CNT, clearing when the counter counts to the configuration value SSF _ VAL, and waiting for the pulse to trigger the counter. When the counter is smaller than SSF _ VAL, the output alarm signal is forced to be effective, and when the counter is larger than or equal to SSF _ VAL, the output alarm signal is input. The alarm signal that is prolonged is the switching signal of the clock. For flexible use, signals can be configured by the CPU forcing the clocks to switch.
The steps a9 to a10 complete the generation and frequency division of the backup clock, complete the extension of the alarm signal, and output the backup clock and the clock switching command required by the customer service.
Step A11, sampling the input smooth clock under the reference clock, generating a counter CLK _ CNT, counting the sampled clock, when the sampled value exceeds the configured maximum and minimum frequency deviation values within the set time, considering the recovered clock frequency deviation is too large, and outputting a clock frequency deviation switching signal. In all clock switching signals, the forced switching priority configured by the CPU is the highest, and the switching signal generated by alarm extension is the switching signal with overlarge frequency offset again.
And step A12, the switched and output clock is sent to PLL, and the required recovered clock is obtained by filtering and frequency multiplication in PLL and sent to serial-parallel converter for use as reference clock.
The embodiment of the invention completes the clock recovery function of the client service. The whole implementation process is simple, the use is flexible, and the use of various customer services can be supported.
To implement the method, an embodiment of the present invention further provides an apparatus for providing a reference clock for a serial-to-parallel converter, as shown in fig. 2, the apparatus including:
a clock recovery unit 202, configured to recover a service clock from service clock information of an optical transmission frame;
a reference clock generating unit 201, configured to generate reference clocks at the transmitting side and the receiving side of the serial-to-parallel converter by using the recovered traffic clock.
Here, the clock recovery unit 202 is specifically configured to extract information of a service clock from an optical transmission frame, and generate gap information of the service clock; correcting the generated service clock gap information; and processing the corrected service clock gap information to recover the service clock.
Here, the service clock information may include: the number of bits in a frame and the number of system clocks in an optical transmission frame.
Here, the reference clock generating unit 201 is further configured to generate a backup clock; completing the switching between the backup clock and the recovered service clock; the reference clock generating unit 201 generates reference clocks of a transmitting side and a receiving side of a serial-to-parallel converter using the recovered traffic clock, including: and generating reference clocks of the transmitting side and the receiving side of the serial-parallel converter by utilizing the switching between the recovered service clock and the backup clock.
The generated backup clock can be generated according to the service clock information of the optical transmission frame; the method for generating the backup clock may be as follows: generating a backup clock by adopting self-oscillation;
here, the reference clock generating unit 201 is specifically configured to generate a backup clock by using a self-oscillation; the generating of the backup clock by the reference clock generating unit 201 using the self-oscillation includes: configuring a self-oscillation clock parameter according to the service clock information of the optical transmission frame, generating self-oscillation clock gap information, and dividing the frequency of the self-oscillation clock gap information to obtain the backup clock; and generating an alarm signal, and switching the backup clock and the service clock according to a switching instruction generated by the alarm signal.
Here, the service clock information of the optical transmission frame may include: the number of bits in a frame and the number of system clocks in an optical transmission frame.
Accordingly, the generating the backup clock using the natural vibration may include: firstly, two parameters of a self-oscillation clock are configured, a self-oscillation clock notch is output according to sigma-delta operation, frequency division is carried out on the clock notch generated by self-oscillation, and the clock after frequency division is a backup clock.
Here, the reference clock generating unit 201 is further configured to extend an alarm signal; seamless switching between the service clock and the backup clock can be realized through prolonging the alarm signal.
Wherein the switching instruction generated according to the alarm signal comprises: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction; the priority order of the switching instructions is as follows: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction; here, the frequency offset switching instruction refers to a frequency offset switching instruction for switching to the backup clock, and may be generated when a frequency offset value of the service clock obtained by sampling is greater than configured maximum and minimum frequency offset values by sampling the recovered service clock.
In the apparatus for providing a reference clock for a serial-to-parallel converter according to the embodiment of the present invention, the clock recovery unit recovers a service clock from service clock information of an optical transmission frame, and then the reference clock generation unit generates the reference clock by using the recovered service clock.
In practical applications, the reference clock generating Unit 201 and the clock recovery Unit 202 may be implemented by a Central Processing Unit (CPU), a microprocessor Unit (MPU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), or the like located in a terminal.
The embodiment of the invention also provides a client for providing a reference clock for the serial-parallel converter, and the client comprises any one of the devices for providing the reference clock for the serial-parallel converter.
Fig. 3 is a schematic structural diagram of an apparatus for providing a reference clock for a serial-to-parallel converter according to a preferred embodiment of the present invention, as shown in fig. 3, the apparatus comprising: the alarm processing module 301, the frequency offset detection module 302, the client clock information extraction module 303, the gap conversion module 304, the frequency division module 305, the clock natural vibration module 308, the frequency division module 307, and the PLL module 306, where the frequency division module 305 and the frequency division module 307 may be one frequency division module.
The client clock information extraction module 303, the gap conversion module 304 and the frequency division module 305 may serve as the clock recovery unit;
the alarm processing module 301, the frequency offset detection module 302, the PLL module 306, the clock natural oscillation module 308, the notch conversion module 304, and the frequency division module 307 may serve as the reference clock generating unit.
In the process of providing a reference clock for a serial-to-parallel converter, the apparatus shown in fig. 3, the client clock information extraction module 303 extracts clock valid information of a client service from an OTU frame, where the valid information includes: the number Cm of the M blocks of the effective payload and the bit remainder sigma Cnd value of the M blocks; according to the two values, the bit number Cn of one frame in the OTU frame is calculated, and the system clock number CNT of one frame is counted, and the time when the information is prepared is marked as A point.
Carrying out sigma-delta operation on the bit number Cn and the clock number CNT to output a clock gap signal of the customer service;
comparing Cn + CN _ RM with CNT, if Cn + CN _ RM > is equal to CNT, the output clock gap is valid, and simultaneously storing the difference value between Cn + CN _ RM and CNT in CN _ RM; if Cn + CN _ RM < CNT, the output clock notch is invalid and the Cn + CN _ RM value is stored in CN _ RM. Wherein, the value of CN-RM is the value stored in the memory.
After that, the counter S _ CNT counts, and when S _ CNT > is equal to CNT, 1 is set to count again, indicating that the above comparison operation is completed, and the values of Cn and CNT are prepared at point a, and this time is denoted as point B.
Further, the number of clocks between the point a and the point B is calculated by the counter AB _ CNT, and since there is jitter in the traffic rate, if the value of the AB _ CNT is smaller than a certain value, there is a case where the time of the point B is ready but the clock information is not ready yet at the point a, in this case, the system will use the last clock information to participate in the operation again, and so on, and the recovery rate will be wrong. Once this occurs, taking half of the Cn and CNT values at this time at point B, sigma-delta operation is performed, after which the distance between points a and B is pulled apart, thus preventing errors.
Here, the certain value may be determined according to conditions such as a rate and a bit width of the service, and according to requirements of actual situations.
Further, the client clock information extraction module 303 inputs the recovered clock gap information to the gap conversion module 304, the gap conversion module 304 adjusts and smoothes the clock gap, and then sends the adjusted clock gap to the frequency division module 305 for frequency division.
The gap transition module 304 performs the following operations: firstly, whether the interface FIFO is in a position of being too low or too high is judged according to the monitored interface FIFO waterline. And for the position where the waterline is too high, adding an effective signal into the input notch within the configured adjustment time to accelerate the recovered clock to enable the waterline to descend, and stopping adjustment after the waterline descends to a reasonable position. And for the position of the waterline which is too low, deleting an effective signal from the input notch within the configured adjustment time, slowing down the recovered clock, enabling the waterline to start rising, and stopping adjustment after the waterline rises to a reasonable position. The process needs reasonable configuration and adjustment time, so that the adjusted clock notch frequency offset meets the requirements.
The gap transition module 304 may then transition and smooth the bit width of the adjusted clock gap according to the requirements of the customer service clock. If the bit width of the input clock gap is nbit and needs to be converted into mbit, the configuration values are one multiple of m and one multiple of n. Generating two counters M _ CNT and MS _ CNT; counting the number of input clock gaps by using a counter M _ CNT, and when the counted value is more than or equal to the multiple of M, setting the counter M _ CNT to be 1 for counting again; counting the number of clocks by the counter MS _ CNT, and outputting a counting value MS _ VAL by the counter MS _ CNT when the M _ CNT is more than or equal to a multiple of n, and setting the counter MS _ CNT to be 1 for counting again.
And then, after sigma-delta operation is carried out on the configured value which is the multiple of n and the statistic value MS _ VAL, the output is the converted clock gap. It is also necessary to prevent switching errors during switching by monitoring at point A, B as described above.
After the process of processing the clock notch by the notch converting module 304 is finished, the output clock notch information is transmitted to the frequency dividing module 305, the frequency dividing module 305 performs frequency dividing processing on the clock notch information, the specific frequency dividing module 305 is used for configuring a frequency dividing parameter N1, starting a counter N _ CNT, counting the input clock notch, when the count value of the counter N _ CNT is greater than or equal to N1, negating the output signal, and when the count value of the counter N _ CNT is less than N1, keeping the output signal unchanged, thus completing the frequency division of 2 × N1 of the clock notch, and the divided clock is a recovered smooth clock.
The gap switching module 304 completes the clock gap switching, and the frequency dividing module 305 completes the frequency division of the clock gap, and outputs the smooth clock required by the customer service.
The transmitting side and the receiving side of the serial-parallel converter need to use two reference clocks, while the clock recovery is realized at the transmitting side of the serial-parallel converter, and in order to save cost, the embodiment of the invention enables the transmitting side and the receiving side to share one reference clock and only uses the recovered service clock. However, when the OTN service is abnormal or the data recovery is incorrect, the service clock cannot be recovered, and thus the receiving side cannot work due to the common reference clock, which is not allowed, in this embodiment of the present invention, a self-oscillation generation backup clock and a clock switching function are used to solve the problem.
And the clock self-oscillation module 308 is configured to configure two parameters of the self-oscillation clock, and output a clock notch of the self-oscillation according to sigma-delta operation. Then, the frequency division module 307 is used to configure a frequency division parameter n2, and frequency division is performed on the clock notch generated by the natural oscillation by 2 × n2, and the frequency-divided clock is a backup clock.
The alarm processing module 301 is configured to extend an alarm signal, sample an input client alarm signal, generate a pulse when the alarm signal is valid to invalid, start a counter, clear the counter when the counter counts a configuration value, and wait for the pulse to trigger the counter; when the counter is smaller than the configuration value, the output alarm signal is forced to be effective; when the value is larger than or equal to the configuration value, the alarm signal is output as input. The alarm signal that is prolonged is the switching signal of the clock. In addition, when the device is attached to a client for use, a signal can be configured through a CPU of the client to forcibly switch the clock.
Here, the alert signal may be from a client; when the alarm signal is valid to invalid, the data will not be restored to normal immediately, but will be normal after a period of time, so the alarm signal needs to be extended to realize seamless switching between the service clock and the backup clock.
The clock self-oscillation module 308, the gap conversion module 304, and the frequency division module 307 generate a backup clock, and the alarm processing module 301 completes the extension of the alarm signal and outputs the backup clock and the clock switching signal of the client service.
The frequency offset detection module 302 samples an input smooth clock under a reference clock, starts a counter CLK _ CNT, counts the sampled clock, and outputs a clock frequency offset switching signal when the sampled value exceeds configured maximum and minimum frequency offset values within a certain time, and the recovered clock frequency offset is considered to be too large.
In all clock switching signals, the forced switching priority configured by the CPU is the highest, and the switching signal generated by alarm extension is the switching signal with overlarge frequency offset again.
The switched reference clock is sent to the PLL module 306, and the required reference clock is obtained by filtering and frequency multiplication inside the PLL module 306 and sent to the serial-to-parallel converter to be used as the reference clock.
In addition, in practical applications, the alarm processing module 301, the frequency offset detection module 302, the client clock information extraction module 303, the gap conversion module 304, the frequency division module 305, the clock self-oscillation module 308, the frequency division module 307, and the PLL module 306 may be implemented by a Central Processing Unit (CPU), a Microprocessor (MPU), a Digital Signal Processor (DSP), a Field Programmable Gate Array (FPGA), or the like, which are located in a terminal.
The method, the device and the client for providing the reference clock for the serial-parallel converter provided by the embodiment of the invention recover the service clock from the service clock information of the optical transmission frame; generating reference clocks of a transmitting side and a receiving side of a serial-parallel converter by using the recovered service clock; furthermore, the embodiment of the present invention may combine the switching between the backup clock and the recovered service clock, so that a common reference clock can be provided for the transmitting side and the receiving side of the serial-parallel converter, and on the basis of saving design cost, the situation that the receiving side cannot normally operate due to the abnormal operation of the service clock recovered by the transmitting side when the transmitting side and the receiving side of the serial-parallel converter share one reference clock can be effectively avoided.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (7)
1. A method of providing a reference clock for a serial to parallel converter, the method comprising:
recovering a service clock from service clock information of the optical transmission frame;
generating reference clocks of a transmitting side and a receiving side of a serial-parallel converter by using the recovered service clock; the method further comprises the following steps:
generating a backup clock; completing the switching between the backup clock and the recovered service clock;
the generating reference clocks of a transmitting side and a receiving side of a serial-parallel converter by using the recovered service clock comprises:
generating reference clocks of a transmitting side and a receiving side of the serial-parallel converter by utilizing the switching between the recovered service clock and the backup clock; wherein the generating backup clock is: generating a backup clock by adopting self-oscillation;
the method for generating the backup clock by adopting the self-oscillation comprises the following steps: configuring a self-oscillation clock parameter according to the service clock information of the optical transmission frame, generating self-oscillation clock gap information, and dividing the frequency of the self-oscillation clock gap information to obtain the backup clock;
and generating an alarm signal, and switching the backup clock and the service clock according to a switching instruction generated by the alarm signal.
2. The method of claim 1, wherein completing the switch between the backup clock and the service clock further comprises: prolonging the alarm signal;
the switching instruction generated according to the alarm signal comprises: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction;
the priority order of the switching instructions is as follows: and a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction.
3. The method of claim 1, wherein recovering the traffic clock from the traffic clock information of the optical transmission frame comprises:
extracting information of a service clock from an optical transmission frame to generate gap information of the service clock;
correcting the generated service clock gap information;
and processing the corrected service clock gap information to recover the service clock.
4. An apparatus for providing a reference clock for a serial to parallel converter, the apparatus comprising:
a clock recovery unit, configured to recover a service clock from service clock information of an optical transmission frame;
a reference clock generating unit, configured to generate reference clocks at a transmitting side and a receiving side of a serial-to-parallel converter using the recovered service clock; wherein the content of the first and second substances,
the reference clock generating unit is also used for generating a backup clock; completing the switching between the backup clock and the recovered service clock;
the reference clock generating unit generates reference clocks of a transmitting side and a receiving side of the serial-parallel converter by using the recovered service clock, and comprises: generating reference clocks of a transmitting side and a receiving side of the serial-parallel converter by utilizing the switching between the recovered service clock and the backup clock; wherein the content of the first and second substances,
the reference clock generating unit is specifically configured to generate a backup clock by using a natural oscillation;
the reference clock generating unit generates the backup clock by adopting the self-oscillation, and comprises the following steps: configuring a self-oscillation clock parameter according to the service clock information of the optical transmission frame, generating self-oscillation clock gap information, and dividing the frequency of the self-oscillation clock gap information to obtain the backup clock; and generating an alarm signal, and switching the backup clock and the service clock according to a switching instruction generated by the alarm signal.
5. The apparatus of claim 4,
the reference clock generating unit is also used for prolonging the alarm signal;
the switching instruction generated according to the alarm signal comprises: a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction;
the priority order of the switching instructions is as follows: and a forced switching instruction, an alarm extension switching instruction and a frequency offset switching instruction.
6. The apparatus of claim 4,
the clock recovery unit is specifically configured to extract information of a service clock from an optical transmission frame, and generate gap information of the service clock; correcting the generated service clock gap information; and processing the corrected service clock gap information to recover the service clock.
7. A client for providing a reference clock for a serial to parallel converter, the client comprising: the device of any one of claims 4 to 6.
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| Application Number | Priority Date | Filing Date | Title |
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| CN201510595446.8A CN106550289B (en) | 2015-09-17 | 2015-09-17 | Method, device and client for providing reference clock for serial-parallel converter |
| PCT/CN2016/095372 WO2017045502A1 (en) | 2015-09-17 | 2016-08-15 | Method and apparatus for providing reference clock to serial-parallel converter and client |
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| CN201510595446.8A CN106550289B (en) | 2015-09-17 | 2015-09-17 | Method, device and client for providing reference clock for serial-parallel converter |
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|---|---|---|---|---|
| CN101150875A (en) * | 2006-09-20 | 2008-03-26 | 中兴通讯股份有限公司 | A device and method for switching mapping modes |
| CN103051422A (en) * | 2012-12-18 | 2013-04-17 | 中兴通讯股份有限公司 | Processing method and device of delay between signals |
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| US8565605B2 (en) * | 2009-12-15 | 2013-10-22 | Broadcom Corporation | Burst mode to continuous mode converter |
| CN103354493B (en) * | 2013-06-26 | 2016-06-29 | 华为技术有限公司 | A kind of clock recovery circuitry, photoreceiver and passive optical network equipment |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101150875A (en) * | 2006-09-20 | 2008-03-26 | 中兴通讯股份有限公司 | A device and method for switching mapping modes |
| CN103051422A (en) * | 2012-12-18 | 2013-04-17 | 中兴通讯股份有限公司 | Processing method and device of delay between signals |
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| WO2017045502A1 (en) | 2017-03-23 |
| CN106550289A (en) | 2017-03-29 |
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