Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Utility Patent
1998-10-14
2001-01-02
Patel, Ajit (Department: 2738)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C370S467000, C370S279000
Utility Patent
active
06169746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a signal transmission apparatus for transmitting and receiving digital data related to video signals, audio signals and so on, and more particularly to a signal transmission apparatus to which standard specification of a high speed serial bus is applied.
2. Description of the Background Art
IEEE 1394-1995 (which represents IEEE Standard for a High Performance Serial Bus IEEE Std IEEE 1394-1995, hereinafter simply referred to as “1394”) is a specification of a serial bus for high speed data transmission in serial manner. Transmission rates of 100 Mbps, 200 Mbps and 400 Mbps (“bps” stands for bit/sec) are specified in 1394, and various corresponding controller LSIs have been commercially available.
Different from the conventional networks such as Ethernet, the feature of 1394 resides in that it specifies a scheme for synchronous transfer suitable for real time information transfer required especially in the field of motion pictures and music. The standard specification 1394 is applied for a digital camera, allowing transfer of video data recorded in digital manner. At present, application not only to the digital camera but also to a digital tuner, a digital video disk (DVD), a personal computer, a hard disk and a printer has been studied.
FIGS. 14A and 14B
show appearances of conventional 6-pin plug and 4-pin plug specified in 1394.
FIGS. 15A
to
15
C show the shape of the plug of FIG.
14
B. These figures are excerpts from IEEE Standard for a High Performance Serial Bus IEEE Std IEEE1394-1995.
FIGS. 15A
to
15
C represents the top, side and a contact surface with the jack of the plug shown in
FIG. 14B
, respectively. As the plug has 6 electrodes P
1
to P
6
, it is difficult to reduce the size thereof.
The 1394 standard is for transferring two types of signals, that is, data and strobe, by using two pairs, that is, a total of four lines by differentiation, utilizing electric signals (when 6 pins are provided, remaining two are used for transmitting power), and operation over a length of 4.5 m is specified. As an extended specification of the standard, a specification defining an operation at a high speed of 800 Mbps of higher over a long distance of 50 m, for example, has been studied, and in order to implement the operation in accordance with the extended specification, a method of transmission utilizing light has been proposed. This method of transmission utilizes two optical fibers, one allotted for outgoing and the other allotted for incoming signals independently from each other for transmission.
FIG. 16
shows shapes of conventionally proposed optical jack and plug (RECEPTACLE).
FIG. 17
represents state of signals flowing through a cable at the time of data transmission in accordance with 1394 standard in a prior art example and an embodiment of the present invention. In this figure, the portion denoted by “arb” requires bidirectional simultaneous communication. Referring to
FIG. 1
, the plug connects to optical fibers. The respective optical fibers allow the simultaneous bidirectional communication corresponding to the portion denoted by “arb” of
FIG. 17
, by a combination of unidirectional signal lines which serve to input and output signals.
Japanese Patent Laying-Open No. 10-164107 discloses a method of application of an optical fiber in accordance with 1394 standard. The technique disclosed in this laid-open application is silent about the number of optical fibers used. However, it is impossible by the described method to reduce the number of optical fibers to be used to only one, simply by converting a code notifying transmission rate used in accordance with 1394 standard to a digital symbol. The reason is as follows. If only such a simple conversion is performed and two controllers (referred to as nodes) in accordance with 1394 standard connected by the optical fiber transmit digital signals over the optical fiber in asynchronous manner, it becomes necessary for each node to emit light by an LED or laser for signal transmission and, at the same time, to receive optical signal at a light receiving element the optical signal transmitted from the counterpart node. In other words, light emission and light reception must be done simultaneously by one same node. If this is realized by one optical fiber, the light emitted from the node of itself is reflected at an end surface of the optical fiber or the like and returns superposed on the optical signal transmitted from the counterpart node, which returning light eventually appearing as noise on the received signal. Because of this noise, signal transmission is impossible when the number of optical fibers is simply reduced to one.
As described above, the technique for increasing the transmission rate and to elongate the transmission path has been under development, in which technique signal transmission is performed by applying optical fibers to 1394 standard.
When 1394 standard employing two optical fibers, one for outgoing and the other for incoming signals, is applied to an information equipment, however, connectors and cables including the plug occupy large space in the information equipment, hindering reduction in size of the information equipment. Accordingly, the use at present of 1394 standard employing two optical fibers for the outgoing and incoming signals is limited to one in that the jack is embedded in a wall for transferring data between rooms.
When a method of signal transfer utilizing two optical fibers is applied as it is to signal transfer using only one optical fiber, normal signal transmission operation cannot be ensured, as light emitted from one node and reflected interferes with the light receiving operation of the node itself.
Further, according to 1394 standard, the shapes of the plug and the jack constituting a connector are determined, at least four metal lines are necessary for electrical connection of four signal lines, and a shield is necessary for suppressing generation of radio wave noise derived from high speed operation. Therefore, it is difficult in accordance with this standard to reduce the size of the cable or the connector.
Further, among information equipments, there has already been ones provided with a jack for digital audio optical transmission (EIAJ CP-1201 digital audio interface), as an optical interface. If such an information equipment is additionally provided with the interface function in accordance with 1394 standard, two different types of jacks are necessary for digital transmission/reception, hindering reduction in size of the equipment.
SUMMARY OF THE INVENTION
Therefore, an object of the present invention is to provide a signal transmission apparatus which allows reduction in sizes of a cable, a jack and a plug related to signal transmission path, reduction in electric noise and in power consumption.
The above described objects can be attained by the signal transmission apparatus for transmitting data in serial manner by mutual communication with another apparatus, including a cable connected to one end of the signal transmission apparatus, handling data as two types of signals for bidirectional simultaneous transmission; a communication path connected to the other end of the signal transmission apparatus for communication with the aforementioned another signal transmission apparatus; a first converting unit receiving data from the cable, converting the received data to one type of signal and outputting it to the communication path in data transmission; a second converting unit receiving one type of signal from the communication path, converting the received signal to data and outputting it to the cable, in data transmission; and a control unit for controlling the communication operation of the signal transmission apparatus in data transmission. The control unit grants transmission priority alternately to the signal transmission apparatuses in a control sequence of communication operation using the communication path.
Therefore, the data consisting of two types of signals
Nishimura Takashi
Sumi Kazuyuki
Ueda Toru
Wakai Hirohisa
Conlin David G.
Dike Bronstein, Roberts & Cushman LLP
Nguyen Hanh
Patel Ajit
Sharp Kabushiki Kaisha
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