US20010014924A1 - Clock adjustment method and apparatus - Google Patents
Clock adjustment method and apparatus Download PDFInfo
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- US20010014924A1 US20010014924A1 US09/767,963 US76796301A US2001014924A1 US 20010014924 A1 US20010014924 A1 US 20010014924A1 US 76796301 A US76796301 A US 76796301A US 2001014924 A1 US2001014924 A1 US 2001014924A1
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04J—MULTIPLEX COMMUNICATION
- H04J3/00—Time-division multiplex systems
- H04J3/02—Details
- H04J3/06—Synchronising arrangements
- H04J3/062—Synchronisation of signals having the same nominal but fluctuating bit rates, e.g. using buffers
- H04J3/0632—Synchronisation of packets and cells, e.g. transmission of voice via a packet network, circuit emulation service [CES]
Definitions
- the present invention relates to a technique allowing communications between a computer and a network such as a switched telephone network.
- USB universal serial bus
- An object of the present invention is to provide a clock adjustment method and apparatus allowing stable and reliable voice communication between a computer and a network without generating noise due to slips of voice data.
- an apparatus connecting a first network and a second network to transfer data between them, wherein the first and second networks operate at different clock frequencies, respectively includes: a first interface to the first network; a second interface to the second network; a buffer memory connected to the first interface, for storing data to be transferred to one of the first and second networks; a clock converter connected between the buffer memory and the second interface, performing a clock conversion according to a controlled clock signal corresponding to the first network and an extracted clock signal that is extracted from the second network; a buffer monitor for monitoring an amount of data stored in the buffer memory to produce a buffer status signal; and a clock adjuster for adjusting the controlled clock signal depending on the buffer status signal.
- the clock adjuster may change a frequency of the controlled clock signal so that the amount of data stored in the buffer memory is kept at a predetermined level.
- the clock adjuster may change a frequency of the controlled clock signal by an amount within a permissible frame clock error which may occur in the first interface.
- an apparatus includes: a USB (universal serial bus) interface to a USB bus connected to the personal computer; a network interface to the switched telephone network; a transmission buffer memory for storing transmission digital voice data that the personal computer transmits; a reception buffer memory for storing reception digital voice data received from the switched telephone network via the network interface; a PCM modulator for modulating the transmission digital voice data to produce a transmission PCM signal; a PCM demodulator for demodulating a reception PCM signal to produce the reception digital voice data; a transmission clock converter connecting the PCM modulator to the network interface, performing a clock conversion according to a controlled clock signal corresponding to the USB interface and an extracted clock signal that is extracted from the second network; a reception clock converter connecting the network interface to the PCM demodulator, performing a clock conversion according to the controlled clock signal and the extracted clock signal; a buffer monitor for monitoring an amount of data stored in each of the transmission and reception buffer memories to produce a buffer status signal; and a clock switching controller for switching
- the clock switching controller may switch a frequency of the controlled clock signal so that the amount of data stored in the buffer memory is kept at a predetermined level.
- the plurality of predetermined frequencies may be a normal frequency, a lower frequency, and a higher frequency, wherein a difference between each of the lower and higher frequencies and the normal frequency falls into a range within a permissible frame clock error which may occur in the USB interface.
- the permissible frame clock error may be 5% of a normal frame clock of the USB bus.
- the transmission clock converter may include: a first coder for coding the transmission PCM signal to produce a transmission analog voice signal according to the controlled clock signal; and a first decoder for decoding the transmission analog voice signal to produce network-side transmission PCM signal according to the extracted clock signal.
- the reception clock converter may include: a second coder for coding network-side reception PCM signal to produce a network-side reception analog voice signal according to the extracted clock signal; and a second decoder for decoding the network-side reception analog voice signal to produce the reception PCM signal according to the controlled clock signal.
- the digital voice data may be transferred through the USB bus in an isochronous mode.
- the transmission buffer memory and the reception buffer memory may be FIFO (first-in-first-out) memories, respectively.
- the transmission buffer memory may include a plurality of FIFO memories and the reception buffer memory comprises a plurality of FIFO memories.
- a control method for a telephone terminal connecting a personal computer and a switched telephone network to transfer voice data between them includes the steps of: storing digital voice data to be transferred to one of the personal computer and the switched telephone network in a buffer memory; monitoring an amount of data stored in the buffer memory to produce a buffer status signal; adjusting a frequency of a controlled clock signal corresponding to the personal computer depending on the buffer status signal; extracting an extracted clock signal from the switched telephone network; and converting an operation clock between the personal computer and the switched telephone network according to the controlled clock signal and the extracted clock signal.
- FIG. 1 is a block diagram showing the configuration of a clock adjustment apparatus according to an embodiment of the present invention
- FIG. 2 is a diagram showing a clock adjustment operation of the embodiment when transferring data from a PC to a telephone network
- FIG. 3 is a diagram showing a clock adjustment operation of the embodiment when transferring data from the telephone network to the PC.
- a personal computer (PC) 1 and a telephone terminal 3 are connected via a USB bus 2 .
- the telephone terminal 3 includes a clock adjustment apparatus according to an embodiment of the present invention and is connected to a switched telephone network 4 .
- the telephone terminal 3 is provided with a USB interface 11 allowing isochronous communication with the PC 1 through the USB bus 2 .
- the USB bus 2 allows 16-byte voice data to be transferred for each frame of 1 msec in the isochronous mode.
- the output terminal of the USB interface 11 is connected to a PCM (pulse code modulation) modulator 12 through a FIFO (first-in first-out) memory section 101 - 104 .
- the input terminal of the USE interface 11 is connected to a PCM demodulator 13 through a FIFO memory section 201 - 204 .
- Each FIFO memory section may be composed of a single FIFO memory or a plurality of FIFO memories connected in series.
- the FIFO memory section between the USE interface 11 and the PCM modulator 12 is composed of 16-byte FIFO memories 101 - 104 and the FIFO memory section between the USB interface 11 and the PCM demodulator 13 is composed of 16-byte FIFO memories 201 - 204 .
- reception voice data when 16-byte reception voice data enters the FIFO memory section 201 - 204 for the first time, the reception voice data is sequentially transferred through the FIFO memories 204 - 202 and stored in the FIFO memory 201 . In this manner, reception voice data is sequentially stored in the FIFO memory section starting from the FIFO memory 201 .
- the PCM modulator 12 and PCM demodulator 13 are connected to a USB-side coder/decoder (CODEC) 14 , which is connected to a line-side CODEC 15 .
- the line-side CODEC 15 is connected to the switched telephone network 4 via a line interface 16 .
- the line interface 16 transmits and receives an 8-bit PCM signal for each frame of 125 ⁇ sec to and from the switched telephone network 4 .
- the USB-side CODEC 14 receives a transmission PCM signal from the PCM modulator 12 and converts it into a transmission analog signal.
- the line-side CODEC 15 receives the transmission analog signal from the USB-side CODEC 14 and converts it into a line-transmission PCM signal to be transmitted to the switched telephone network 4 .
- the line-side CODEC 15 converts it into a reception analog signal.
- the USE-side CODEC 14 receives the reception analog signal from the line-side CODEC 15 to convert it into a USB-reception PCM signal and outputs it to the PCM demodulator 13 .
- the USB-side CODEC 14 converts a transmission PCM signal into analog according to a controlled clock signal supplied from a clock generation switch 17 .
- the line-side CODEC 15 converts the transmission analog signal into digital according to an operation clock signal supplied from a clock supplier 18 connected to a clock extractor 19 .
- the clock extractor 19 is connected to the line interface 16 to extract a line clock signal from the switched telephone network 4 .
- the clock supplier 18 produces the operation clock signal from the line clock signal to operate the line-side CODEC 15 . In this manner, clock conversion is performed such that a PCM signal is converted into an analog signal according to one clock signal and the resultant analog signal is converted into a PCM signal according to the other clock signal.
- the telephone terminal 3 is further provided with a FIFO status monitor 20 that monitors the statuses of respective ones of the FIFO memory sections 101 - 104 and 201 - 204 . More specifically, the FIFO status monitor 20 monitors the amount of transmission data storing in the FIFO memory section 101 - 104 and monitors the amount of reception data storing in the FIFO memory section 201 - 204 . For example, each of the FIFO memories 101 - 104 and 201 - 204 outputs a full-status signal to the FIFO status monitor 20 when the FIFO memory becomes full and outputs an available/empty-status signal until the FIFO memory is full. The details will be described later (see FIGS. 2 and 3).
- the FIFO status monitor 20 outputs a FIFO status signal to a clock controller 21 , which controls the clock generation switch 17 depending on the FIFO status so that an appropriate clock frequency is supplied to the USB-side CODEC 14 .
- a clock controller 21 which controls the clock generation switch 17 depending on the FIFO status so that an appropriate clock frequency is supplied to the USB-side CODEC 14 .
- each of the 16-byte FIFO memories 101 - 104 outputs a full-status signal to the FIFO status monitor 20 when the FIFO memory has stored 16-byte transmission voice data for each frame and outputs an empty-status signal when the FIFO memory stores no data.
- the FIFO status monitor 20 outputs one of four FIFO status signals to the clock controller 21 depending on the amount of transmission voice data stored in the FIFO memories 101 - 104 .
- the clock controller 21 controls the clock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14 .
- the period of the normal-frequency clock is 125 ⁇ sec.
- the clock generation switch 17 supplies the USB-side CODEC 14 with a frame pulse signal having a period of 125 ⁇ sec.
- the clock controller 21 controls the clock generation switch 17 so that a lower-frequency (lower-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to increase the amount of data stored in the FIFO memory section.
- the clock controller 21 controls the clock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14 .
- the lower frequency is lower than the normal frequency by an amount within a permissible frame clock error of ⁇ 5% which may occur in the USB interface 11 and the PC clock can accommodate.
- the lower-frequency clock signal has a period of 132 ⁇ sec.
- the clock generation switch 17 switches the period of a frame pulse signal supplied to the USB-side CODEC 14 from 125 ⁇ sec to 132 ⁇ sec.
- the clock controller 21 controls the clock generation switch 17 so that a higher-frequency (higher-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to decrease the amount of data stored in the FIFO memory section.
- the clock controller 21 controls the clock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14 .
- the higher frequency is higher than the normal frequency by an amount within a permissible frame clock error of ⁇ 5% which may occur in the USB interface 11 and the PC clock can accommodate.
- the higher-frequency clock signal has a period of 117 ⁇ sec.
- the clock generation switch 17 switches the period of a frame pulse signal supplied to the USB-side CODEC 14 from 125 ⁇ sec to 117 ⁇ sec.
- transmission voice data sequentially store into the FIFO memories 101 - 104 as described before.
- the clock generation switch 17 starts supplying the normal-frequency clock signal to the USB-side CODEC 14 under control of the clock controller 21 as described before. If the transmission voice data are stored in the FIFO memories 104 to 102 , the clock controller 21 switches the normal-frequency clock signal to the higher-frequency clock signal. Contrarily, when the FIFO memories 101 - 103 become empty, the clock controller 21 switches the normal-frequency clock signal to the lower-frequency clock signal.
- each of the 16-byte FIFO memories 201 - 204 outputs a full-status signal to the FIFO status monitor 20 when the FIFO memory has stored 16-byte reception voice data for each frame and outputs an empty-status signal when the FIFO memory stores no data.
- the FIFO status monitor 20 outputs one of four FIFO status signals to the clock controller 21 depending on the amount of reception voice data stored in the FIFO memories 201 - 204 .
- the clock controller 21 controls the clock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14 .
- the period of the normal-frequency clock is 125 ⁇ sec.
- the clock generation switch 17 supplies the USB-side CODEC 14 with a frame pulse signal having a period of 125 ⁇ sec.
- the clock controller 21 controls the clock generation switch 17 so that a higher-frequency (higher-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to increase the amount of data stored in the FIFO memory section.
- the clock controller 21 controls the clock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14 .
- the higher frequency is higher than the normal frequency by an amount within a permissible frame clock error of ⁇ 5% which may occur in the USB interface 11 and the PC clock can accommodate.
- the higher-frequency clock signal has a period of 117 ⁇ sec.
- the clock controller 21 controls the clock generation switch 17 so that a lower-frequency (lower-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to decrease the amount of data stored in the FIFO memory section.
- the clock controller 21 controls the clock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14 .
- the lower frequency is lower than the normal frequency by an amount within a permissible frame clock error of ⁇ 5% which may occur in the USE interface 11 and the PC clock can accommodate.
- the lower-frequency clock signal has a period of 132 ⁇ sec.
- the clock generation switch 17 starts supplying the USB-side CODEC 14 with the normal-frequency clock signal. Accordingly, reception voice data sequentially store into the FIFO memories 201 - 204 as described before.
- the USB interface 11 starts sequentially transferring the stored voice data to the PC 1 through the USB bus 2 in the isochronous mode.
- the clock controller 21 switches the normal-frequency clock signal to the lower-frequency clock signal. Contrarily, when the FIFO memories 202 - 204 become empty, the clock controller 21 switches the normal-frequency clock signal to the higher-frequency clock signal.
- the FIFO memory section is composed of a plurality of FIFO memories connected in series. It is also possible to use a single FIFO memory having a necessary capacity.
Abstract
Description
- 1. Field of the Invention
- The present invention relates to a technique allowing communications between a computer and a network such as a switched telephone network.
- 2. Description of the Related Art
- With the widespread use of personal computers (PCs), the demands for voice communication between personal computers through a telephone network are growing. Conventionally, voice data communication is performed using telephone terminal equipment connecting a personal computer to the telephone network. More specifically, the telephone terminal equipment is provided with a phase-locked loop circuit that is used to synchronize to a clock signal extracted from the telephone network.
- It is necessary to synchronize all devices connected to the same communication line and therefore the USB (universal serial bus) interface is used to synchronize the clock of a PC to the clock signal extracted from the telephone network. However, the clock of a PC cannot be controlled from outside. Accordingly, it is difficult or almost impossible to establish synchronization of a PC.
- When clock synchronization is not perfectly established, the clock of a PC that is used to digitize a voice signal and the transmission clock of the telephone network are independently running. In the case where the PC clock frequency is higher than the transmission clock frequency of the telephone network, the digital signal generated by the PC cannot be transmitted to the telephone network. Contrarily, when the PC clock frequency is lower than the transmission clock frequency of the telephone network, data to be transmitted to the telephone network is partly lost, which causes noise due to slips of voice data.
- An object of the present invention is to provide a clock adjustment method and apparatus allowing stable and reliable voice communication between a computer and a network without generating noise due to slips of voice data.
- According to an aspect of the present invention, an apparatus connecting a first network and a second network to transfer data between them, wherein the first and second networks operate at different clock frequencies, respectively, includes: a first interface to the first network; a second interface to the second network; a buffer memory connected to the first interface, for storing data to be transferred to one of the first and second networks; a clock converter connected between the buffer memory and the second interface, performing a clock conversion according to a controlled clock signal corresponding to the first network and an extracted clock signal that is extracted from the second network; a buffer monitor for monitoring an amount of data stored in the buffer memory to produce a buffer status signal; and a clock adjuster for adjusting the controlled clock signal depending on the buffer status signal.
- The clock adjuster may change a frequency of the controlled clock signal so that the amount of data stored in the buffer memory is kept at a predetermined level. The clock adjuster may change a frequency of the controlled clock signal by an amount within a permissible frame clock error which may occur in the first interface.
- According to another aspect of the present invention, an apparatus includes: a USB (universal serial bus) interface to a USB bus connected to the personal computer; a network interface to the switched telephone network; a transmission buffer memory for storing transmission digital voice data that the personal computer transmits; a reception buffer memory for storing reception digital voice data received from the switched telephone network via the network interface; a PCM modulator for modulating the transmission digital voice data to produce a transmission PCM signal; a PCM demodulator for demodulating a reception PCM signal to produce the reception digital voice data; a transmission clock converter connecting the PCM modulator to the network interface, performing a clock conversion according to a controlled clock signal corresponding to the USB interface and an extracted clock signal that is extracted from the second network; a reception clock converter connecting the network interface to the PCM demodulator, performing a clock conversion according to the controlled clock signal and the extracted clock signal; a buffer monitor for monitoring an amount of data stored in each of the transmission and reception buffer memories to produce a buffer status signal; and a clock switching controller for switching a frequency of the controlled clock signal to one selected from a plurality of predetermined frequencies depending on the buffer status signal.
- The clock switching controller may switch a frequency of the controlled clock signal so that the amount of data stored in the buffer memory is kept at a predetermined level. The plurality of predetermined frequencies may be a normal frequency, a lower frequency, and a higher frequency, wherein a difference between each of the lower and higher frequencies and the normal frequency falls into a range within a permissible frame clock error which may occur in the USB interface. The permissible frame clock error may be 5% of a normal frame clock of the USB bus.
- The transmission clock converter may include: a first coder for coding the transmission PCM signal to produce a transmission analog voice signal according to the controlled clock signal; and a first decoder for decoding the transmission analog voice signal to produce network-side transmission PCM signal according to the extracted clock signal. The reception clock converter may include: a second coder for coding network-side reception PCM signal to produce a network-side reception analog voice signal according to the extracted clock signal; and a second decoder for decoding the network-side reception analog voice signal to produce the reception PCM signal according to the controlled clock signal.
- The digital voice data may be transferred through the USB bus in an isochronous mode.
- The transmission buffer memory and the reception buffer memory may be FIFO (first-in-first-out) memories, respectively.
- The transmission buffer memory may include a plurality of FIFO memories and the reception buffer memory comprises a plurality of FIFO memories.
- A control method for a telephone terminal connecting a personal computer and a switched telephone network to transfer voice data between them, includes the steps of: storing digital voice data to be transferred to one of the personal computer and the switched telephone network in a buffer memory; monitoring an amount of data stored in the buffer memory to produce a buffer status signal; adjusting a frequency of a controlled clock signal corresponding to the personal computer depending on the buffer status signal; extracting an extracted clock signal from the switched telephone network; and converting an operation clock between the personal computer and the switched telephone network according to the controlled clock signal and the extracted clock signal.
- FIG. 1 is a block diagram showing the configuration of a clock adjustment apparatus according to an embodiment of the present invention;
- FIG. 2 is a diagram showing a clock adjustment operation of the embodiment when transferring data from a PC to a telephone network; and
- FIG. 3 is a diagram showing a clock adjustment operation of the embodiment when transferring data from the telephone network to the PC.
- Referring to FIG. 1, a personal computer (PC)1 and a
telephone terminal 3 are connected via a USB bus 2. Thetelephone terminal 3 includes a clock adjustment apparatus according to an embodiment of the present invention and is connected to a switchedtelephone network 4. - The
telephone terminal 3 is provided with aUSB interface 11 allowing isochronous communication with the PC 1 through the USB bus 2. Here, it is assumed that the USB bus 2 allows 16-byte voice data to be transferred for each frame of 1 msec in the isochronous mode. The output terminal of theUSB interface 11 is connected to a PCM (pulse code modulation)modulator 12 through a FIFO (first-in first-out) memory section 101-104. The input terminal of theUSE interface 11 is connected to aPCM demodulator 13 through a FIFO memory section 201-204. - Each FIFO memory section may be composed of a single FIFO memory or a plurality of FIFO memories connected in series. Here, the FIFO memory section between the
USE interface 11 and thePCM modulator 12 is composed of 16-byte FIFO memories 101-104 and the FIFO memory section between theUSB interface 11 and thePCM demodulator 13 is composed of 16-byte FIFO memories 201-204. - As described later, when 16-byte transmission voice data enters the FIFO memory section101-104 for the first time,, the transmission voice data is sequentially transferred through the FIFO memories 101-103 and stored in the
FIFO memory 104, In this manner, transmission voice data is sequentially stored in the FIFO memory section starting from theFIFO memory 104. - Contrarily, when 16-byte reception voice data enters the FIFO memory section201-204 for the first time, the reception voice data is sequentially transferred through the FIFO memories 204-202 and stored in the
FIFO memory 201. In this manner, reception voice data is sequentially stored in the FIFO memory section starting from theFIFO memory 201. - The
PCM modulator 12 andPCM demodulator 13 are connected to a USB-side coder/decoder (CODEC) 14, which is connected to a line-side CODEC 15. The line-side CODEC 15 is connected to the switchedtelephone network 4 via aline interface 16. Here, it is assumed that theline interface 16 transmits and receives an 8-bit PCM signal for each frame of 125 μsec to and from the switchedtelephone network 4. - The USB-
side CODEC 14 receives a transmission PCM signal from thePCM modulator 12 and converts it into a transmission analog signal. The line-side CODEC 15 receives the transmission analog signal from the USB-side CODEC 14 and converts it into a line-transmission PCM signal to be transmitted to the switchedtelephone network 4. When receiving a reception PCM signal from theline interface 16, the line-side CODEC 15 converts it into a reception analog signal. The USE-side CODEC 14 receives the reception analog signal from the line-side CODEC 15 to convert it into a USB-reception PCM signal and outputs it to thePCM demodulator 13. - The USB-
side CODEC 14 converts a transmission PCM signal into analog according to a controlled clock signal supplied from aclock generation switch 17. The line-side CODEC 15 converts the transmission analog signal into digital according to an operation clock signal supplied from aclock supplier 18 connected to aclock extractor 19. Theclock extractor 19 is connected to theline interface 16 to extract a line clock signal from the switchedtelephone network 4. Theclock supplier 18 produces the operation clock signal from the line clock signal to operate the line-side CODEC 15. In this manner, clock conversion is performed such that a PCM signal is converted into an analog signal according to one clock signal and the resultant analog signal is converted into a PCM signal according to the other clock signal. - The
telephone terminal 3 is further provided with aFIFO status monitor 20 that monitors the statuses of respective ones of the FIFO memory sections 101-104 and 201-204. More specifically, the FIFO status monitor 20 monitors the amount of transmission data storing in the FIFO memory section 101-104 and monitors the amount of reception data storing in the FIFO memory section 201-204. For example, each of the FIFO memories 101-104 and 201-204 outputs a full-status signal to theFIFO status monitor 20 when the FIFO memory becomes full and outputs an available/empty-status signal until the FIFO memory is full. The details will be described later (see FIGS. 2 and 3). - The FIFO status monitor20 outputs a FIFO status signal to a
clock controller 21, which controls theclock generation switch 17 depending on the FIFO status so that an appropriate clock frequency is supplied to the USB-side CODEC 14. Hereafter, a clock adjustment operation according to the present embodiment will be described in detail. - Referring to FIG. 2, each of the 16-byte FIFO memories101-104 outputs a full-status signal to the FIFO status monitor 20 when the FIFO memory has stored 16-byte transmission voice data for each frame and outputs an empty-status signal when the FIFO memory stores no data. Here, the FIFO status monitor 20 outputs one of four FIFO status signals to the
clock controller 21 depending on the amount of transmission voice data stored in the FIFO memories 101-104. - As shown in FIG. 2, when the
FIFO memories FIFO memories clock controller 21 controls theclock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14. Here, the period of the normal-frequency clock is 125 μsec. In other words, theclock generation switch 17 supplies the USB-side CODEC 14 with a frame pulse signal having a period of 125 μsec. - When only the
FIFO memory 104 is full and the remaining FIFO memories 101-103 are empty, it means that the frequency of the PC-side clock is lower than that of the controlled clock generated by theclock generation switch 17. Accordingly, theclock controller 21 controls theclock generation switch 17 so that a lower-frequency (lower-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to increase the amount of data stored in the FIFO memory section. When the amount of data stored in the FIFO memory section becomes normal, theclock controller 21 controls theclock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14. - The lower frequency is lower than the normal frequency by an amount within a permissible frame clock error of ±5% which may occur in the
USB interface 11 and the PC clock can accommodate. For example, the lower-frequency clock signal has a period of 132 μsec. In other words, theclock generation switch 17 switches the period of a frame pulse signal supplied to the USB-side CODEC 14 from 125 μsec to 132 μsec. - When the FIFO memories102-104 are full and only the
FIFO memory 101 is empty, which is caused by frame pulse jitter on the USB bus 2 and/or by the frequency of the PC-side clock higher than that of the controlled clock generated by theclock generation switch 17. Accordingly, theclock controller 21 controls theclock generation switch 17 so that a higher-frequency (higher-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to decrease the amount of data stored in the FIFO memory section. When the amount of data stored in the FIFO memory section becomes normal, theclock controller 21 controls theclock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14. - The higher frequency is higher than the normal frequency by an amount within a permissible frame clock error of ±5% which may occur in the
USB interface 11 and the PC clock can accommodate. For example, the higher-frequency clock signal has a period of 117 μsec. In other words, theclock generation switch 17 switches the period of a frame pulse signal supplied to the USB-side CODEC 14 from 125 μsec to 117 μsec. - When the
PC 1 starts data transmission in the isochronous mode, transmission voice data sequentially store into the FIFO memories 101-104 as described before. When theFIFO memories clock generation switch 17 starts supplying the normal-frequency clock signal to the USB-side CODEC 14 under control of theclock controller 21 as described before. If the transmission voice data are stored in theFIFO memories 104 to 102, theclock controller 21 switches the normal-frequency clock signal to the higher-frequency clock signal. Contrarily, when the FIFO memories 101-103 become empty, theclock controller 21 switches the normal-frequency clock signal to the lower-frequency clock signal. - Referring to FIG. 3, each of the 16-byte FIFO memories201-204 outputs a full-status signal to the FIFO status monitor 20 when the FIFO memory has stored 16-byte reception voice data for each frame and outputs an empty-status signal when the FIFO memory stores no data. Here, the FIFO status monitor 20 outputs one of four FIFO status signals to the
clock controller 21 depending on the amount of reception voice data stored in the FIFO memories 201-204. - As shown in FIG. 3, when the
FIFO memories FIFO memories clock controller 21 controls theclock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14. Here, the period of the normal-frequency clock is 125 μsec. In other words, theclock generation switch 17 supplies the USB-side CODEC 14 with a frame pulse signal having a period of 125 μsec. - When only the
FIFO memory 201 is full and the remaining FIFO memories 202-204 are empty, it means that the frequency of the PC-side clock is higher than that of the controlled clock generated by theclock generation switch 17. Accordingly, theclock controller 21 controls theclock generation switch 17 so that a higher-frequency (higher-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to increase the amount of data stored in the FIFO memory section. When the amount of data stored in the FIFO memory section becomes normal, theclock controller 21 controls theclock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14. - As described before, the higher frequency is higher than the normal frequency by an amount within a permissible frame clock error of ±5% which may occur in the
USB interface 11 and the PC clock can accommodate. Here, the higher-frequency clock signal has a period of 117 μsec. - When the FIFO memories201-203 are full and only the
FIFO memory 204 is empty, it means that the frequency of the PC-side clock is lower than that of the controlled clock generated by theclock generation switch 17. Accordingly, theclock controller 21 controls theclock generation switch 17 so that a lower-frequency (lower-speed) clock signal with respect to the normal-frequency clock signal is supplied to the USB-side CODEC 14 to decrease the amount of data stored in the FIFO memory section. When the amount of data stored in the FIFO memory section becomes normal, theclock controller 21 controls theclock generation switch 17 so that a normal-frequency (normal-speed) clock signal is supplied to the USB-side CODEC 14. - The lower frequency is lower than the normal frequency by an amount within a permissible frame clock error of ±5% which may occur in the
USE interface 11 and the PC clock can accommodate. Here, the lower-frequency clock signal has a period of 132 μsec. - When the line-
side CODEC 15 starts operating in response to reception of data from the switchedtelephone network 4, theclock generation switch 17 starts supplying the USB-side CODEC 14 with the normal-frequency clock signal. Accordingly, reception voice data sequentially store into the FIFO memories 201-204 as described before. When theFIFO memories USB interface 11 starts sequentially transferring the stored voice data to thePC 1 through the USB bus 2 in the isochronous mode. When the reception voice data are stored in theFIFO memories 201 to 203, theclock controller 21 switches the normal-frequency clock signal to the lower-frequency clock signal. Contrarily, when the FIFO memories 202-204 become empty, theclock controller 21 switches the normal-frequency clock signal to the higher-frequency clock signal. - As described above, data transmission and reception can be performed by the
telephone terminal 3 according to the clock adjustment operations as shown in FIGS. 2 and 3, respectively. Accordingly, even in the case where the PC clock is not synchronized to the line clock of the switchedtelephone network 4, the clock adjustment allows continuous voice data transmission without data slip or noise, resulting in improved stability and reliability on voice data communication. - In the above embodiment, the FIFO memory section is composed of a plurality of FIFO memories connected in series. It is also possible to use a single FIFO memory having a necessary capacity.
Claims (16)
Applications Claiming Priority (3)
Application Number | Priority Date | Filing Date | Title |
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JP2000-016701 | 2000-01-26 | ||
JP2000016701A JP3465227B2 (en) | 2000-01-26 | 2000-01-26 | Telephone terminal device |
JP016701/2000 | 2000-01-26 |
Publications (2)
Publication Number | Publication Date |
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US20010014924A1 true US20010014924A1 (en) | 2001-08-16 |
US6456702B2 US6456702B2 (en) | 2002-09-24 |
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US09/767,963 Expired - Fee Related US6456702B2 (en) | 2000-01-26 | 2001-01-24 | Clock adjustment method and apparatus |
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US (1) | US6456702B2 (en) |
JP (1) | JP3465227B2 (en) |
AU (1) | AU1670201A (en) |
Cited By (10)
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US20050182871A1 (en) * | 2002-06-14 | 2005-08-18 | Busse Frederick L. | Method and apparatus for improving bus utilization |
WO2005076123A1 (en) * | 2004-02-10 | 2005-08-18 | Infineon Technologies Ag | Method and circuit for differential clock pulse compensation between two clock-pulse systems |
US20050289377A1 (en) * | 2004-06-28 | 2005-12-29 | Ati Technologies Inc. | Apparatus and method for reducing power consumption in a graphics processing device |
WO2007013044A1 (en) * | 2005-07-29 | 2007-02-01 | Nxp B.V. | Data stream synchronization |
US20070283077A1 (en) * | 2006-05-30 | 2007-12-06 | Christian Klein | Memory and Memory Communication System |
US20080028249A1 (en) * | 2006-03-31 | 2008-01-31 | Agrawal Parag V | System and method for adaptive frequency scaling |
US20080062892A1 (en) * | 2006-09-07 | 2008-03-13 | Honeywell International Inc. | High speed bus protocol with programmable scheduler |
US9467150B2 (en) | 2015-03-02 | 2016-10-11 | Sandisk Technologies Llc | Dynamic clock rate control for power reduction |
US9753522B2 (en) * | 2015-03-02 | 2017-09-05 | Sandisk Technologies Llc | Dynamic clock rate control for power reduction |
US9929972B2 (en) | 2011-12-16 | 2018-03-27 | Qualcomm Incorporated | System and method of sending data via a plurality of data lines on a bus |
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US7114086B2 (en) * | 2002-01-04 | 2006-09-26 | Ati Technologies, Inc. | System for reduced power consumption by monitoring instruction buffer and method thereof |
US7243253B1 (en) * | 2002-06-21 | 2007-07-10 | Redback Networks Inc. | Repeating switching of a cross-connect and a timing source in a network element through the use of a phase adjuster |
US7278047B2 (en) * | 2002-10-14 | 2007-10-02 | Lexmark International, Inc. | Providing different clock frequencies for different interfaces of a device |
JP2004221951A (en) * | 2003-01-15 | 2004-08-05 | Alps Electric Co Ltd | Method for correcting jitter of transmission data |
US7231468B2 (en) * | 2003-06-06 | 2007-06-12 | Intel Corporation | Future activity list for peripheral bus host controller |
US7478260B2 (en) * | 2003-10-20 | 2009-01-13 | Hewlett-Packard Development Company, L.P. | System and method for setting a clock rate in a memory card |
KR101090440B1 (en) * | 2003-12-08 | 2011-12-06 | 삼성전자주식회사 | Apparatus and method for controlling buffer data level in receiver of data communication system, and apparatus and method for playing streaming data with adaptive clock synchronizer |
JP4716001B2 (en) * | 2005-03-08 | 2011-07-06 | 日本電気株式会社 | Communication system between CPUs |
JP2007266856A (en) * | 2006-03-28 | 2007-10-11 | Aiphone Co Ltd | Transmitter-receiver of voice synchronization type, signal processing system, and signal processor used assembled in the transmitter-receiver of voice synchronization type |
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Family Cites Families (1)
Publication number | Priority date | Publication date | Assignee | Title |
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GB2301978A (en) * | 1995-06-09 | 1996-12-18 | Ibm | Voice processing system |
-
2000
- 2000-01-26 JP JP2000016701A patent/JP3465227B2/en not_active Expired - Fee Related
-
2001
- 2001-01-24 US US09/767,963 patent/US6456702B2/en not_active Expired - Fee Related
- 2001-01-29 AU AU16702/01A patent/AU1670201A/en not_active Abandoned
Cited By (17)
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US20050182871A1 (en) * | 2002-06-14 | 2005-08-18 | Busse Frederick L. | Method and apparatus for improving bus utilization |
KR100850078B1 (en) * | 2004-02-10 | 2008-08-04 | 인피니언 테크놀로지스 아게 | Method and circuit for differential clock pulse compensation between two clock-pulse systems |
US7876720B2 (en) * | 2004-02-10 | 2011-01-25 | Infineon Technologies Ag | Method and circuit for differential clock pulse compensation between two clock-pulse systems |
US20070165678A1 (en) * | 2004-02-10 | 2007-07-19 | Frank Huertgen | Method and circuit for differential clock pulse compensation between two clock-pulse systems |
WO2005076123A1 (en) * | 2004-02-10 | 2005-08-18 | Infineon Technologies Ag | Method and circuit for differential clock pulse compensation between two clock-pulse systems |
US20050289377A1 (en) * | 2004-06-28 | 2005-12-29 | Ati Technologies Inc. | Apparatus and method for reducing power consumption in a graphics processing device |
US7500123B2 (en) * | 2004-06-28 | 2009-03-03 | Ati Technologies Ulc | Apparatus and method for reducing power consumption in a graphics processing device |
US20080186972A1 (en) * | 2005-07-29 | 2008-08-07 | Nxp B.V. | Data Stream Synchronization |
WO2007013044A1 (en) * | 2005-07-29 | 2007-02-01 | Nxp B.V. | Data stream synchronization |
US20080028249A1 (en) * | 2006-03-31 | 2008-01-31 | Agrawal Parag V | System and method for adaptive frequency scaling |
US8250394B2 (en) * | 2006-03-31 | 2012-08-21 | Stmicroelectronics International N.V. | Varying the number of generated clock signals and selecting a clock signal in response to a change in memory fill level |
US20070283077A1 (en) * | 2006-05-30 | 2007-12-06 | Christian Klein | Memory and Memory Communication System |
US8352695B2 (en) * | 2006-05-30 | 2013-01-08 | Lantiq Deutschland Gmbh | Selectable access rates in a memory and memory communication system |
US20080062892A1 (en) * | 2006-09-07 | 2008-03-13 | Honeywell International Inc. | High speed bus protocol with programmable scheduler |
US9929972B2 (en) | 2011-12-16 | 2018-03-27 | Qualcomm Incorporated | System and method of sending data via a plurality of data lines on a bus |
US9467150B2 (en) | 2015-03-02 | 2016-10-11 | Sandisk Technologies Llc | Dynamic clock rate control for power reduction |
US9753522B2 (en) * | 2015-03-02 | 2017-09-05 | Sandisk Technologies Llc | Dynamic clock rate control for power reduction |
Also Published As
Publication number | Publication date |
---|---|
US6456702B2 (en) | 2002-09-24 |
AU1670201A (en) | 2001-08-02 |
JP3465227B2 (en) | 2003-11-10 |
JP2001211228A (en) | 2001-08-03 |
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