JP4023203B2 - Signal transmission system - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a signal transmission system that transmits and receives signals between a master node and a plurality of slave nodes via a transmission path.
[0002]
[Prior art]
In recent years, with the improvement of semiconductor integration technology, the data processing speed of LSI has been dramatically increased. Along with this, an improvement in signal transmission capability is required for a wiring board on which a semiconductor integrated circuit is mounted. In particular, recently, a so-called parallel processing architecture including a plurality of high-speed CPU chips has been adopted in a personal computer as well, in a server type system corresponding to a higher model. The parallel processing architecture technology is described in, for example, “Hideharu Amano, Parallel Computer, Shosodo, pp. 6-13”. According to this, when configuring a system including a plurality of modules that perform data processing such as a CPU, the coupling method between modules is classified into a bus coupling type, a switch coupling type, and a coupling network type. Of these, the bus coupling type is not suitable for coupling a large number of modules, but has advantages such as a simple structure, a small amount of hardware, and excellent extensibility compared to other modules. It is widely used in commercial computers such as personal computers and computer application products such as page printers.
[0003]
The mounting of the inter-module coupling part of the parallel processing system requires a large number of connection connectors and wirings, so that the communication capacity and wiring density have been improved by multilayering and miniaturization of the wirings. However, the limit is being reached due to signal delay and transmission waveform distortion caused by inter-wiring capacitance and connection wiring resistance. In addition, electromagnetic noise (EMI: Electromagnetic Interference) becomes a serious problem due to an increase in operating speed.
[0004]
As described above, the processing capability of the data processing apparatus is often limited by the transmission capability of the wiring board bus. In order to overcome the limitations of electric buses, the use of an in-system optical connection technology called optical interconnection has been studied. The outline of the optical interconnection technology is as follows. .33, pp. 81-86, 1994 ”,“ Osamu Wada, April 1993 Electronics, pp. 52-55 ”, various forms have been proposed depending on the contents of the system configuration. . According to this technology, it is possible to reduce electromagnetic noise while being able to operate at a higher frequency than electric, eliminating the need for physical connection of bus signal lines, and transmission bandwidth by multiplexing using wavelength, strength, etc. Can be expanded, and simultaneous bi-directional communication is possible. For example, Japanese Patent Application Laid-Open No. 10-98439 discloses an optical fiber using this type of technology.
[0005]
On the other hand, unlike the optical fiber transmission technology, the spatial light transmission technology enables simultaneous communication between multiple ports, and therefore has good consistency with the above-described bus-coupled parallel processing architecture. A related technique is described in JP-A-10-123350. This technology realizes optical communication between ports installed on the end face of a flat light guide, and diffuses incident signal light and transmits it to the opposite end face to realize broadcast communication. By using multiple transmissions, multiple independent broadcast communications are performed simultaneously.
[0006]
As a signal transmission system technology that applies such spatial light transmission, in order to alleviate the problem of transmission skew between signals and reduce the number of transmission lines, a plurality of electric signal lines are converted in parallel and serially. A system has been proposed in which a serial signal is converted into an optical signal and transmitted via a spatial light transmission medium. In particular, here, only a data signal and a frame signal are transmitted from the transmission node to the reception node, and a clock signal is not transmitted. The frame signal represents the transmission frequency of the electric signal line, and the clock signal represents the transmission frequency of the serial signal obtained after parallel-serial conversion. The clock signal is necessary for latching the serial signal at the receiving node. Here, the frequency is multiplied from the received frame signal by means such as a PLL (Phase Locked Loop) circuit to automatically generate the clock signal. As a result, it is not necessary to transmit a clock signal having a high frequency particularly in optical transmission, and a transmission band necessary for optical parts and circuit parts constituting the transmission path can be narrowed, and a transmission system can be easily realized.
[0007]
[Problems to be solved by the invention]
In this type of signal transmission system, when a master node and a plurality of slave nodes are connected via a high-speed serial transmission path, timing adjustment is performed in order to transmit and receive data between both nodes. At this time, timing adjustment is individually performed between the master node and each slave node, and switching of the slave node requires a time on the order of milliseconds, and there is a problem that the switching is too slow.
[0008]
An object of the present invention is to provide a signal transmission system that can smoothly adjust timing between nodes connected by a transmission path.
[0009]
[Means for Solving the Problems]
The above object is a signal transmission system in which a master node and a plurality of slave nodes are connected via a transmission line, and a timing adjustment sequence that is slower than data transmission is used when adjusting timing between the master node and slave nodes. Achieved by a signal transmission system.
Here, the timing adjustment sequence can include a low-speed timing adjustment command transmitted prior to the high-speed timing adjustment pattern data. The timing adjustment command can be sent to the same transmission path as the timing adjustment pattern data, and can be accompanied by the frequency of the source signal before being multiplied during data transmission.
[0010]
The timing adjustment method according to the present invention is a timing adjustment method between a master node and a slave node connected via a transmission line, and introduces a timing adjustment operation that introduces a timing adjustment sequence that is slower than data transmission. Is to do.
With this configuration, it is possible to smoothly adjust the timing between the nodes connected by the transmission path.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a diagram illustrating a configuration example of a signal transmission system to which the present invention is applied. In this example, a master node 10 and a plurality of slave nodes 1, 2, and 3 are connected via a transmission line 4 as shown in the figure. The transmission path 4 is configured using, for example, an optical fiber, and an optical demultiplexer 5 and an optical multiplexer 6 are arranged in the transmission path.
[0012]
The master node 10 includes a transmission unit 11 that transmits an optical signal and a reception unit 12 that receives the optical signal. Similarly, the slave node 1 includes a transmitter 13 that transmits an optical signal and a receiver 14 that receives the optical signal. Each of the slave nodes 2 and 3 has the same configuration as that of the slave node 1.
[0013]
The optical demultiplexer 5 has one optical signal incident port and three output ports. The light guide is configured so that an optical signal having the same amount of light can be obtained at each exit port when an optical signal enters from the entrance port. As the optical demultiplexer 5, for example, a star coupler or the like can be used, and an optical bus described in JP-A-10-123350 and JP-A-10-123374 can also be used. These optical buses obtain signal light having a uniform light intensity level at the exit end face by diffusing the signal light inside the sheet-like optical transmission medium or at the entrance end face.
[0014]
The optical multiplexer 6 includes three optical signal incident ports and one outgoing port. The light guide is configured so that an optical signal having a similar light quantity can be obtained at the exit port regardless of which optical signal is incident from any of the entrance ports. As the optical multiplexer 6, a star coupler or an optical bus can be used as in the optical demultiplexer 5 described above.
[0015]
As a more specific example of the optical demultiplexer 5, a 1 × 8 optical spectrometer is shown in FIG. For example, the optical demultiplexer 5 has an incident light diffusion angle of 0.2 at one end of a translucent light sheet 51 having a thickness of 0.5 mm, a width of 4 mm, a length of 20 mm, and a refractive index of 1.49. A × 40 ° transmission diffusing section 52 is provided, which includes one plastic on the input side and eight plastic or quartz optical fibers 56 (φ0.5 mm, NA0.5) on the output side, metal such as aluminum, It arrange | positions and is comprised as shown in figure on board | substrate 53, such as an acryl. With such an arrangement, it is possible to input and output signals from the same direction, and thus the size of the apparatus can be reduced. Here, when the connection between the optical fiber 56 and the light sheet 51 or the light diffusing unit 52 is configured by abutment of the fiber, variations occur in the fiber protrusion amounts at the end faces of the plurality of optical fibers. For this reason, the gap between the optical sheet or the end face of the diffusing portion and each optical fiber varies, and there is a fear that the transmission loss in the optical fiber having a wide gap increases. For this reason, it is desirable to fill the gap with a light-transmitting resin, and an ultraviolet curable or thermosetting epoxy resin or a soft elastic light-transmitting resin can be used. Note that the periphery of the gap, the entire sheet, or the entire substrate may be sealed. At this time, it is desirable to select a resin whose refractive index is matched to the optical fiber and the optical sheet. The optical multiplexer can be applied as the optical multiplexer 6 by providing the input side of the present optical demultiplexer as the output side, the output side as the input side, and providing the light diffusing section on the incident port side end surface of the light sheet 51.
[0016]
In the signal transmission system configured as described above, when high-speed data transmission is performed between a master node and a slave node, timing adjustment is performed between both nodes. In the timing adjustment in this case, the present invention uses a timing adjustment sequence that is slower than the data transmission. In this timing adjustment sequence, a low-speed timing adjustment command is sent from the master node 10 to the slave node side via the transmission path. Subsequently, the high-speed timing adjustment pattern data and the frame signal are transmitted through the same transmission path. The timing adjustment command sent here is low speed and has the frequency of the source signal before being multiplied during data transmission. For example, when the source signal is 50 MHz and parallel 10-bit input is performed, since the serial transmission speed multiplied by 10 is 500 MHz, a command is transmitted at a low speed of 50 MHz when adjusting timing.
Hereinafter, the timing adjustment operation according to the present invention will be described in more detail.
[0017]
FIG. 3 is a flowchart showing an example of the timing adjustment operation on the slave node side. As shown in the figure, immediately after the start of timing adjustment on the slave node side, slave node ID = 0 is set at step 31. In step 32, ID = ID + 1 is set, and for example, the slave node 1 is selected as a timing adjustment target node. The slave node 1 receives a low-speed command from the master node 10 in step 33, establishes a communication state with the master node 10, and then receives high-speed pattern data in step 34. Similarly, timing adjustment is performed in step 35 at low speed using the received frame signal. If the adjustment cannot be made at once, the timing adjustment is repeated. This timing adjustment is performed as follows, for example.
[0018]
FIG. 4 is a diagram illustrating an example in which timing adjustment is performed by shifting the phase of a frame signal, where (a) shows pattern data, (b) shows a clock signal, and (c) shows a frame signal. The slave node 1 shifts the frame signal that is slower than the clock signal in the direction of the arrow in the figure, for example, in units of 100 ps, and selects an optimum phase so that the pattern data can be correctly received. That is, the reception status of the pattern data is tried for all of the eight phase divisions, the best timing is taken, and the phase is fixed.
[0019]
If the timing adjustment can be taken, it is determined in step 36 whether the slave node ID for which the timing adjustment has been performed matches the set value. If the ID does not match the set value, the process returns to step 32 to return to another setting. Timing adjustment similar to the above is performed for the slave node ID. If the ID matches the set value, the process ends.
[0020]
FIG. 5 is a flowchart showing an example of the timing adjustment operation on the master node side. As shown in the figure, the timing adjustment on the master node side is set to slave node ID = 0 in step 41 immediately after the start. In step 42, ID = ID + 1 is set, and for example, the slave node 1 is selected as the timing adjustment target node. The master node 10 sends a low-speed command to the slave node 1 in step 43, establishes a communication state with the slave node 1, and then sends high-speed pattern data in step 44. Then, in order to determine whether or not the timing has been obtained in step 45, an attempt is made to receive pattern data from the slave node 1. As a result, if the pattern data can be received in step 46, OK is returned, and if it cannot be received, NG is returned to the slave node 1. This timing adjustment is performed in step 47 as follows, for example.
[0021]
FIG. 6 is a diagram illustrating an example in which timing adjustment is performed by shifting the phase of pattern data. (A) shows pattern data, (b) shows a clock signal, and (c) shows a frame signal. The slave node 1 shifts the phase of the pattern data in the direction of the arrow in the figure and transmits it to the master node 10. In order to perform this for all of the eight phase divisions, for example, the process returns from step 47 to step 43 to repeat the above processing. The slave node 1 records the phase when OK is received from the master node 10. When these processes are finished for the slave node 1, the process subsequently returns from step 48 to step 42, and the timing adjustment similar to the above is performed for the other slave nodes 2, 3. When these processes are completed for all slave nodes, this timing adjustment operation ends.
[0022]
If there is no response for a certain time after the master node 10 sends the timing adjustment command, or if timing adjustment cannot be performed, an error is output to the upper chip.
[0023]
As described above, in the present invention, a sequence for timing adjustment at a low speed (for example, 50 MHz) at which low-speed transmission can be established between a master node and a slave node capable of high-speed transmission (for example, 500 MHz) is introduced in advance. Timing adjustment is performed between the master node and the slave node. When switching to another slave node after high-speed communication is possible, it can be configured so that another slave node performs transmission in accordance with the timing established by the previous slave node without adjusting the timing. . This is because the clock signal is branched into a plurality of optical demultiplexers such as so-called optical sheet buses, so that subsequent slave nodes can know the timing established in the previous slave node. is there. Therefore, there is no need to individually adjust the timing between the master node and each slave node as in the prior art, and the slave node can be switched at high speed. In addition, it can be executed without securing a new transmission path for timing adjustment.
[0024]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the signal transmission system which can perform the timing adjustment smoothly between the nodes connected by the transmission line can be obtained.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration example of a signal transmission system to which the present invention is applied.
FIG. 2 is a diagram illustrating an example of an optical demultiplexer.
FIG. 3 is a flowchart illustrating an example of a timing adjustment operation on the slave node side.
4A and 4B are diagrams illustrating an example in which timing adjustment is performed by shifting the phase of a frame signal, where FIG. 4A illustrates pattern data, FIG. 4B illustrates a clock signal, and FIG. 4C illustrates a frame signal.
FIG. 5 is a flowchart showing an example of a timing adjustment operation on the master node side.
6A and 6B are diagrams illustrating an example in which timing adjustment is performed by shifting the phase of pattern data. FIG. 6A illustrates pattern data, FIG. 6B illustrates a clock signal, and FIG. 6C illustrates a frame signal.
[Explanation of symbols]
1-3 Slave node 4 Transmission path 5 Optical demultiplexer 6 Optical multiplexer 10 Master node

Claims (3)

A signal transmission system in which a master node and a plurality of slave nodes are connected via a transmission line including an optical demultiplexer for transmitting an optical signal, and when adjusting the timing between the master node and the slave node, compared to when transmitting data A low-speed timing adjustment sequence in which transmission can be established without adjustment is used . In the timing adjustment sequence, a low-speed timing adjustment command is sent from the master node to the slave node via a transmission path, and then a high-speed timing is transmitted. The adjustment pattern data and the frame signal are transmitted via the same transmission path, and the slave node receives the low-speed timing adjustment command from the master node and establishes a communication state with the master node, and then the high-speed The timing adjustment pattern data of Signal transmission system which is characterized in that the timing adjustment using the frame signal signal. Wherein the timing adjustment command, the signal transmission system according to claim 1, wherein the associated frequency of the previous source signal multiplied at the time of data transmission. A timing adjustment method between a master node and a slave node connected via a transmission line including an optical demultiplexer that transmits an optical signal, and a low-speed timing adjustment sequence in which transmission can be established without adjustment compared to data transmission In the timing adjustment sequence, a low-speed timing adjustment command is sent from the master node to the slave node via the transmission line, and then the high-speed timing adjustment pattern data and the frame signal are transmitted through the same transmission line. The slave node receives the low-speed timing adjustment command from the master node and establishes a communication state with the master node, and then receives the high-speed timing adjustment pattern data and also receives it. to make the timing adjustment using the frame signal The timing adjusting method for the butterflies.

Images