JP2012023571A - Communication unit, communication system, and control method of communication unit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication unit, a communication system, and a control method of the communication unit which enable communication between devices to be adequately performed even if the devices have different clock frequencies.SOLUTION: A clock isolation function separates a card edge side port of a PCI Express bridge chip 13 and an optical cable side port as domains operating separate clocks, and a clock (first clock) used in the optical cable side port is supplied from a clock source 14 on a PCI Express/optical cable conversion board 10. A communication unit acquires a clock (second clock) of a printer 400 to be a communication connection destination, and if the frequency of the first clock generated by the clock source 14 is different from the frequency of the second clock, a frequency adjustment unit 15 adjusts in such a way that the first clock frequency will correspond to the second clock frequency.

Description

  The present invention relates to a communication unit, a communication system, and a communication unit control method that are attached to a first device and connect the first device to a second device so as to communicate with each other.

  PCI Express (registered trademark) is known as a high-speed serial interface standard. PCI Express combines high data transfer speed and flexibility to adapt to various applications, and is widely used for expansion boards such as graphics cards. In recent years, the communication protocol of PCI Express has begun to be used for communication between different systems, and a communication adapter (communication unit) having a card edge of the PCI Express standard has been proposed (for example, see Patent Document 1). ).

  However, a communication unit having a conventional PCI Express standard card edge has a clock frequency of a device (first device) to which the communication unit is attached and a clock frequency of a device (second device) as a communication partner. Is assumed to match. For this reason, when the clock frequency of the second device is different from the clock frequency of the first device, there is a problem in that communication fails without being synchronized.

  According to the basic specification of PCI Express, the clock frequency is not defined, but it is defined that the data rate of transmission / reception must match within 600 ppm for the stability. Further, according to the PCI Express CEM specification, the clock frequency is normally defined as 100 MHz ± 300 ppm. However, in reality, there are devices that do not satisfy such regulations. Therefore, the frequency of the clock may be different between the devices that perform communication. In this case, synchronization is not achieved and communication fails.

  The present invention has been made in view of the above, and provides a communication unit, a communication system, and a communication unit control method capable of appropriately performing communication even between devices having different clock frequencies. It is aimed.

  In order to solve the above-described problems and achieve the object, a communication unit according to the present invention is attached to a first device, and connects the first device to a second device so that they can communicate with each other. A communication unit for receiving transfer data from the second device to the first device based on the first clock and a clock source for generating a first clock; and Data transfer means for transmitting transfer data from a device to the second device, clock acquisition means for acquiring a second clock that is a clock of the second device from the second device, and the first Clock frequency adjusting means for adjusting the frequency of the clock to match the frequency of the second clock.

  In addition, the communication system according to the present invention is attached to the first device, the second device, and the first device and connected to the second device via a communication cable. A communication unit that relays communication between a device and the second device, the communication unit including a clock source that generates a first clock, and a clock source that generates the first clock. A data transfer means for receiving transfer data from the second device to the first device and transmitting transfer data from the first device to the second device; and Clock acquisition means for acquiring a second clock that is a clock of the second equipment from the equipment, and clock frequency adjustment means for adjusting the frequency of the first clock so as to coincide with the frequency of the second clock And Characterized in that it obtain.

  The communication unit control method according to the present invention includes a clock source that is attached to a first device and connected to a second device via a communication cable, and generates a first clock. Data transfer means for receiving transfer data from the second device to the first device based on a clock and transmitting the transfer data from the first device to the second device. A method for controlling a communication unit, the step of obtaining a second clock, which is a clock of the second device, from the second device, and the frequency of the first clock, Adjusting to match the frequency.

  According to the present invention, there is an effect that communication can be appropriately performed between devices having different clock frequencies.

FIG. 1 is a schematic configuration diagram of a printing system according to an embodiment. FIG. 2 is a diagram for explaining the tree structure of the PCI Express standard in the server and the printer. FIG. 3 is a diagram for explaining a tree structure of the PCI Express standard in the server and the printer. FIG. 4 is a diagram illustrating a transmission path between the server and the printer. FIG. 5 is a diagram for explaining the PCI Express / optical cable conversion board according to the first embodiment. FIG. 6 is a plan view showing an example of a specific component layout in the PCI Express / optical cable conversion board. FIG. 7 is a flowchart illustrating an example of processing for adjusting the frequency of the clock (first clock) generated by the clock source on the PCI Express / optical cable conversion board. FIG. 8 is a diagram for explaining the PCI Express / optical cable conversion board according to the second embodiment.

  Exemplary embodiments of a communication unit, a communication system, and a communication unit control method according to the present invention will be explained below in detail with reference to the accompanying drawings. Hereinafter, a print system including a server and a printer as information devices including a communication unit will be described as an example. Note that applicable apparatuses (systems) are not limited to these.

(First embodiment)
FIG. 1 is a schematic configuration diagram of a print system 100 according to the present embodiment. The print system 100 includes a server 200 and a printer 400 connected to the server 200 by an optical active cable 300. The server 200 is a so-called print server, and is connected to a plurality of terminals (for example, PCs) 600 via the network 500.

  As shown in FIG. 2 as an example, each of the server 200 and the printer 400 includes a group of devices connected in accordance with a tree structure topology defined by the PCI Express standard. As shown in FIG. 3 as an example, the tree structure topology defined in the PCI Express standard is a tree-type configuration with the root complex as the apex, and is a topology in which the root complex and the endpoint are connected. is there.

  As shown in FIG. 4, the server 200 has a socket (PCI Express socket 220) that conforms to the PCI Express standard mounted on its motherboard 210. A card adapter 230 as a communication unit is attached to the PCI Express socket 220.

  As shown in FIG. 4, the printer 400 has a socket (PCI Express socket 420) that conforms to the PCI Express standard on the motherboard 410. A card adapter 430 is attached to the PCI Express socket 420.

  The card adapter 230 on the server 200 side and the card adapter 430 on the printer 400 side are connected to each other by an optical active cable 300 incorporating an optical transceiver. Accordingly, the server 200 and the printer 400 are connected via the optical active cable 300 so as to be capable of optical communication, and high-speed information transmission is performed between the server 200 and the printer 400 using light as a medium.

  Here, image information (black image information, cyan image information, magenta image information, and yellow image information) is transmitted from the server 200 to the printer 400 in the form of lossless compression data of a raster image. The printer 400 forms a color image according to the received image information.

  In the printing system 100 configured as described above, in the present embodiment, the following PCI Express / optical cable conversion board is used as the card adapter (communication unit) 230 on the server 200 side.

  FIG. 5 is a diagram illustrating a configuration example of the PCI Express / optical cable conversion board 10 used as the card adapter (communication unit) 230 on the server 200 side. The PCI Express / optical cable conversion board 10 includes a PCI Express card edge connector 11 conforming to the PCI Express standard (PCI Express-Gen1 / Gen2-x1, 2, 4, 8, 16, etc.) and, for example, SFP, QSFP, XFP, etc. An optical cable connector 12 conforming to the standard and a PCI Express bridge chip (transfer means) 13 having a clock isolation function are provided. The clock isolation function is a function that separates the operation area of the PCI Express bridge chip 13 into a plurality of areas that operate with individual clocks.

  The PCI Express card edge connector 11 is connected to the card edge side port of the PCI Express bridge chip 13 by a serial signal line formed on the substrate. The PCI Express bridge chip 13 is connected to the motherboard 210 of the server 200 via the PCI Express card edge connector 11.

  The optical cable connector 12 is connected to the optical cable side port of the PCI Express bridge chip 13 by a serial signal line formed on the substrate. For example, a communication cable incorporating an optical transceiver, that is, one end side of an optical active cable 300 having an electrical / optical conversion function is attached to the optical cable connector 12. The other end side of the optical active cable 300 is connected to the printer 400 side. The PCI Express bridge chip 13 is connected to the printer 400 via the optical cable connector 12 and the optical active cable 300.

  FIG. 6 is a plan view showing an example of a specific component layout in the PCI Express / optical cable conversion board 10.

  The PCI Express / optical cable conversion board 10 is mounted with a clock transmission cable connector 16 and a connector 17 in addition to the optical cable connector 12 and the PCI Express bridge chip 13 described above on a substrate 10a. The PCI Express card edge connector 11 is formed on both surfaces near one end of the substrate 10a. In addition, the codes | symbols L11 and L12 in FIG. 6 are 105 mm and 130 mm, for example.

  Further, in FIG. 6, a region where the serial signal lines on the substrate 10 a are wired with the highest priority is indicated by hatching. The serial signal line is a PCI Express transmission line, and as described above, between the PCI Express card edge connector 11 and the PCI Express bridge chip 13 and between the PCI Express bridge chip 13 and the optical cable connector 12. Wiring between. Note that the area on the back surface side corresponding to the wiring area is also a wiring area.

  The clock transmission cable connector 16 is a connector (for example, RJ45) to which a clock transmission cable 350 (for example, Ethernet (registered trademark) cable) described later is attached.

  The connector 17 is a connector for supplying electric power to the cooling fan when the cooling fan is attached. The power is supplied from the server 200 via the PCI Express card edge connector 11.

  Further, the PCI Express / optical cable conversion board 10 is provided with a clock source 14 and a frequency adjustment unit 15 as shown in FIG.

  The clock source 14 generates a clock to be supplied to the optical cable side port of the PCI Express bridge chip 13. In other words, the PCI Express bridge chip 13 separates the card edge side port and the optical cable side port as regions operating with different clocks by the above-described clock isolation function. A clock (first clock) used in the optical cable side port is supplied from the clock source 14. As the clock source 14 for generating the first clock, for example, a variable frequency clock generator such as a clock synthesizer or a pulse generator is used. On the other hand, the clock of the card edge side port is supplied from the clock source 250 on the motherboard 210 of the server 200 via the PCI Express card edge connector 11 (third clock).

  The optical cable side port of the PCI Express bridge chip 13 receives the transfer data to the server 200 transmitted from the printer 400 via the optical active cable 300 based on the first clock generated by the clock source 14, and the server Processing for transmitting transfer data from 200 to the printer 400 via the optical active cable 300 is performed. Further, at the card edge side port of the PCI Express bridge chip 13, transfer data from the server 200 to the printer 400 is input based on the third clock supplied from the server 200, and transfer data from the printer 400 is The data is output to the server 200 via the PCI Express card edge connector 11.

  The frequency adjusting unit 15 adjusts the frequency of the first clock generated by the clock source 14. The frequency adjusting unit 15 is connected to a clock transmission cable connector 16. The clock transmission cable 350 is a communication cable used to supply a clock (second clock) generated by the clock source 450 of the printer 400 to the PCI Express bridge chip 13, and one end side is attached to the clock transmission cable connector 16. The other end is connected to the printer 400.

  The frequency adjustment unit 15 inputs the second clock transmitted from the printer 400 via the clock transmission cable 350 from the clock transmission cable connector 16 and detects the frequency of the second clock. The frequency adjustment unit 15 then selects the first clock when the frequency of the first clock generated by the clock source 14 is different from the frequency of the second clock acquired from the printer 400 via the clock transmission cable 350. Is adjusted to match the frequency of the second clock. Then, the first clock whose frequency is adjusted is supplied to the optical cable side port of the PCI Express bridge chip 13.

  In the present embodiment, the PCI Express / optical cable conversion board 10 that relays communication between the server 200 and the printer 400 uses the first clock generated by the clock source 14 to the optical cable side of the PCI Express bridge chip 13. The port is made to work. Therefore, if the frequency of the clock of the printer 400 (second clock generated by the clock source 450) and the frequency of the first clock generated by the clock source 14 on the PCI Express / optical cable conversion board 10 are different, communication is possible. Will fail. Therefore, the PCI Express / optical cable conversion board 10 acquires the second clock from the printer 400 via the clock transmission cable 350 attached to the clock transmission cable connector 16 and the first clock generated by the clock source 14. Is adjusted to the frequency of the first clock by the frequency adjusting unit 15 so as to match the frequency of the second clock.

  FIG. 7 is a flowchart illustrating an example of a process for adjusting the frequency of the first clock generated by the clock source 14. When the first clock generated by the clock source 14 on the PCI Express / optical cable conversion board 10 is, for example, 100.0 MHz and the clock (second clock) of the printer 400 is, for example, 100.1 MHz, PCI Express / optical cable conversion When the optical cable side port of the board 10 is operated using the first clock having a frequency of 100.0 MHz, synchronization fails and communication fails. Therefore, in this embodiment, the PCI Express / optical cable conversion board 10 executes the processing shown in the flowchart of FIG. 7, for example, and the frequency adjustment unit 15 sets the frequency of the first clock generated by the clock source 14 to the printer 400. Communication is enabled by adjusting to 100.1 MHz which is a clock.

  7 is started when the printer 400 is connected to the PCI Express / optical cable conversion board 10 using the optical active cable 300 and the clock transmission cable 350, for example.

  When the process is started, first, in step S101, the frequency adjustment unit 15 determines whether or not to read the clock frequency value (the frequency value of the clock of the device that has communicated in the past) stored in a predetermined memory. Judging. If it is determined that reading is to be performed (step S101: YES), the frequency adjusting unit 15 reads the frequency value stored in the memory in step S102, and the first clock generated by the clock source 14 is read. Adjust the frequency to match the read frequency. On the other hand, if it is determined not to read the frequency value stored in the memory (step S101: NO), the process of step S102 is omitted.

  In the processing in steps S101 and S102, the frequency value of the clock with which communication has been established in the past is held in the memory, and the frequency value of the first clock is read as necessary. By adjusting the value, the frequency value of the first clock is adjusted before link training starts so that communication can be quickly established. Whether or not to read a past frequency value may be determined, for example, based on whether or not the clock transmission cable 350 is attached to the clock transmission cable connector 16. That is, when the clock transmission cable 350 is not attached to the clock transmission cable connector 16, the user does not intentionally attach the clock transmission cable 350 and stores it in the memory because there is experience in connecting the printer 400 in the past. In such a case, the frequency value stored in the memory is read out.

  Next, in step S103, link training with the printer 400 is started by the optical cable side port of the PCI Express bridge chip 13. Link training is a process of confirming whether data is correctly transmitted by transmitting / receiving symbols of a predetermined pattern to / from a communication partner (printer 400 in the case of the present embodiment). It is a process for establishing a communication link between. During the link training, the printer 400 transmits the clock (second clock) of the printer 400 generated by the clock source 450 to the PCI Express / optical cable conversion board 10 via the clock transmission cable 350. . In the PCI Express / optical cable conversion board 10, the second clock sent from the printer 400 is acquired and supplied to the frequency adjustment unit 15 (step S104). The frequency adjustment unit 15 confirms the frequency of the second clock sent from the printer 400.

  Next, at the optical cable side port of the PCI Express bridge chip 13, in step S105, it is determined whether or not a communication link with the printer 400 is established as a result of link training. When the communication link is established (step S105: YES), in step S106, the frequency value of the first clock generated by the clock source 14 at that time is stored in a predetermined memory, and the first clock The process of adjusting the frequency ends.

  On the other hand, when the communication link is established (step S105: NO), the frequency adjustment unit 15 generates the clock source 14 based on the frequency value of the second clock acquired from the printer 400 during the link training. The frequency of the first clock to be adjusted is adjusted to coincide with the frequency of the second clock (step S107). Then, returning to step S103, link training is performed using the first clock whose frequency is adjusted, and the above processing is repeated until a communication link is established with the printer 400.

  As described above in detail with reference to specific examples, according to the present embodiment, the card edge side port and the optical cable side port of the PCI Express bridge chip 13 are respectively set to separate clocks by the clock isolation function. A clock (first clock) used as an optical cable side port is separated and supplied from the clock source 14 on the PCI Express / optical cable conversion board 10. Then, the clock (second clock) of the printer 400 that is the connection destination of communication is acquired, and when the frequency of the first clock generated by the clock source 14 is different from the acquired frequency of the second clock, The frequency adjusting unit 15 adjusts the frequency of the first clock so as to match the frequency of the second clock. Therefore, even when the clock frequency of the printer 400 is not a predetermined frequency value, communication with the printer 400 can be appropriately performed, and devices having different clock frequencies can communicate with each other. Can be connected.

(Second Embodiment)
Next, a second embodiment will be described. FIG. 8 is a diagram illustrating a configuration example of the PCI Express / optical cable conversion board 10 according to the second embodiment. In the present embodiment, the printer 400 transmits a second clock frequency-divided by a predetermined ratio from the printer 400 to the PCI Express / optical cable conversion board 10, and the PCI Express / optical cable conversion board 10 This is an example of restoring by multiplying by a predetermined ratio. In order to realize this, in the present embodiment, a divider 460 that divides the frequency of the second clock generated by the clock source 450 at a predetermined ratio is provided on the printer 400 side. Further, the PCI Express / optical cable conversion board 10 restores the frequency of the second clock transmitted from the printer 400 via the clock transmission cable 350 and input from the clock transmission cable connector 16 by multiplying by a predetermined ratio. A multiplier 18 is provided. Other configurations are the same as those in the first embodiment described above.

  Usually, when long-distance communication exceeding, for example, 100 m is used, if an inexpensive metal cable is used as the clock transmission cable 350, it is difficult to normally transmit and receive a high-frequency clock of 100 MHz. If an optical cable is used as the clock transmission cable 350, transmission and reception can be performed normally even with a high-frequency clock, but there is a problem that the cost is increased. Therefore, in the present embodiment, when the second clock is transmitted from the printer 400 to the PCI Express / optical cable conversion board 10, the frequency of the second clock is set to a predetermined frequency by the frequency divider 460 provided on the printer 400 side. The frequency is divided by a ratio (1 / n times) and then transmitted to the PCI Express / optical cable conversion board 10 via the clock transmission cable 350. Then, on the PCI Express / optical cable conversion board 10 side, the frequency of the second clock acquired from the printer 400 via the clock transmission cable 350 is multiplied by a predetermined ratio (n times) by the multiplier 18 and restored. The adjustment unit 15 is supplied. It should be noted that the predetermined ratio at the time of frequency division / multiplication may be determined in advance as a specified value and set in the frequency division unit 460 and the frequency multiplication unit 18.

  In the present embodiment, the frequency of the second clock generated from the clock source 450 of the printer 400 is divided by 1 / n (for example, 1/10) by the frequency divider 460, and then the clock transmission cable 350 is connected. Via the PCI Express / optical cable conversion board 10 side. The frequency-divided second clock is input from the clock transmission cable connector 16 to the multiplying unit 18, where the frequency is multiplied by n (for example, 10 times) and restored. To be supplied. Then, the frequency adjustment unit 15 compares the restored second clock frequency with the frequency of the first clock generated by the clock source 14 on the PCI Express / optical cable conversion board 10, and determines the frequency value of both. Are different from each other, the frequency of the first clock is adjusted to match the frequency of the second clock. Thus, the second clock can be appropriately transmitted from the printer 400 side to the PCI Express / optical cable conversion board 10 side while using an inexpensive metal cable such as an Ethernet (registered trademark) cable as the clock transmission cable 350. It becomes possible, and long-distance communication exceeding 100 m can be realized at low cost.

  Note that when the second clock is transmitted and received by the method as described above, the waveform of the second clock may be somewhat disturbed. However, the second clock is not used as the clock itself in the PCI Express / optical cable conversion board 10 but is used as information for adjusting the frequency of the first clock generated by the clock source 14. On the Express / optical cable conversion board 10 side, it is only necessary to be able to determine the frequency value of the second clock, so that some waveform disturbance does not cause a problem.

  As described above, the first embodiment and the second embodiment have been specifically described as an application example of the present invention. However, the present invention is not limited to the above-described embodiment as it is, but is in an implementation stage. Thus, various modifications and changes can be made without departing from the scope of the invention. For example, in the above-described embodiment, the configuration on the printer 400 side has been briefly described. However, the same card adapter (communication unit) as the PCI Express / optical cable conversion board 10 mounted on the server 200 is also mounted on the printer 400 side. May be. In this case, in one of the card adapters on the server 200 side and the printer 400 side, the clock isolation of the PCI Express bridge chip 13, the supply of the first clock from the clock source 14, and the first clock by the frequency adjustment unit 15 The frequency may be adjusted. In this case, the functions of both the frequency divider 460 and the multiplier 18 described in the second embodiment are provided on the card adapter, and the clock transmitting side (second clock) and the receiving side are provided. What is necessary is just to use the frequency dividing part 460 and the multiplication part 18 properly by the side to perform.

  The communication system that performs optical communication using the optical active cable 300 has been described above. However, the present invention is not limited to optical communication, and can be widely applied to communication systems of various communication forms. For example, instead of using the optical active cable 300, the present invention is also effective for a communication system that performs communication using a copper wire cable conforming to the PCI Express standard or another cable capable of transmitting a high-speed differential signal. It is applicable to. Moreover, although the said embodiment demonstrated the case where the information communication based on PCI Express specification was performed, it is not limited to this.

10 PCI Express / Optical Cable Conversion Board 11 PCI Express Card Edge Connector 12 Optical Cable Connector 13 PCI Express Bridge Chip 14 Clock Source 15 Frequency Adjustment Unit 16 Clock Transmission Cable Connector 18 Multiplication Unit 200 Server 210 Motherboard 250 Clock Source 300 Optical Active Cable 350 Clock transmission cable 400 Printer 450 Clock source 460 Divider

JP 2010-45763 A

Claims (8)

A communication unit mounted on a first device and configured to connect the first device to a second device so as to be communicable,
A clock source for generating a first clock;
Data transfer means for receiving transfer data from the second device to the first device based on the first clock and transmitting the transfer data from the first device to the second device When,
Clock acquisition means for acquiring a second clock that is a clock of the second device from the second device;
And a clock frequency adjusting means for adjusting the frequency of the first clock so as to match the frequency of the second clock. A card edge connector connected to the motherboard of the first device;
A cable connector to which a communication cable used as a communication medium with the second device is attached;
The data transfer means is supplied with transfer data received from the second device based on the first clock at the port on the cable connector side from the port on the card edge connector side. Output to the first device based on the third clock and the transfer data input from the first device based on the third clock at the port on the card edge connector side. 2. The communication unit according to claim 1, wherein transmission is performed from the port on the connector side to the second device based on the first clock.   The communication unit according to claim 2, wherein the card edge connector is a PCI Express card edge connector conforming to a PCI Express standard.   The communication unit according to claim 2, wherein the communication cable is an optical active cable having an electrical / optical conversion function. The second clock is transmitted from the second device via a clock transmission cable,
The communication unit according to any one of claims 1 to 4, wherein the clock acquisition unit includes a clock transmission cable connector to which the clock transmission cable is attached. The second clock is divided by a predetermined ratio and transmitted from the second device via the clock transmission cable.
6. The communication unit according to claim 5, further comprising a multiplying unit that multiplies and restores the second clock acquired by the clock acquiring unit at the predetermined ratio. A first device, a second device, and a first device that is attached to the first device and connected to the second device via a communication cable and between the first device and the second device A communication unit that relays the communication of
The communication unit is
A clock source for generating a first clock;
Data transfer means for receiving transfer data from the second device to the first device based on the first clock and transmitting the transfer data from the first device to the second device When,
Clock acquisition means for acquiring a second clock that is a clock of the second device from the second device;
And a clock frequency adjusting means for adjusting the frequency of the first clock so as to match the frequency of the second clock. A clock source mounted on the first device and connected to the second device via a communication cable to generate a first clock, and the second device from the second device based on the first clock A method of controlling a communication unit comprising: data transfer means for receiving transfer data to one device and transmitting transfer data from the first device to the second device,
Obtaining a second clock that is a clock of the second device from the second device;
Adjusting the frequency of the first clock so as to coincide with the frequency of the second clock.

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