JP2865810B2 - Bus control device for CATV receiver - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bus control apparatus for a CATV receiver, and more particularly to a hub control apparatus for converting a multi-channel optical multiplex television signal transmitted from a CATV head end into a 4-channel hub. A bus that connects a BS tuner and an encoder in a CATV system in which a TV signal is selected and distributed to each subscriber's BS tuner, and a channel selection signal from the BS tuner is transmitted from the encoder to the hub via the bus. CATV like controlling
The present invention relates to a bus control device for a receiver.

[Related Art] In urban CATV including independent broadcasting and two-way transmission, there is a strong demand for multi-channel and high-quality video signals.
Further, recently, as a transmission medium, an optical fiber having excellent characteristics such as a wide band, low loss, and non-dielectric properties as compared with a coaxial cable has been increasingly used.

As an example of CATV using optical fiber as a transmission medium, FM multiplex HDTV light by demand access method
A CATV system (Research Report of the Institute of Electronics, Information and Communication Engineers, OCS89-51, pp. 7-12, 1989) has been proposed.

FIG. 5 is a schematic block diagram showing the overall configuration of the above-mentioned proposed optical CATV system. In FIG. 5, the optical CA
The TV system includes an optical CATV headend 1, a hub 2, and a subscriber 3. The CATV headend 1 is installed in a CATV broadcasting station, and a camera or VTR that is the source of the MUSE signal
The television signal for 34 channels from the like is FM-modulated by the FM modulator at different carrier frequencies, multiplexed and converted into an optical signal by the electric / optical (E / O) converter 12, and the main optical fiber cable 4 Is transmitted to the hub 2.

The hub 2 is installed on a telephone pole or the like in the vicinity of a plurality of subscribers 3 and, in response to a request from the subscribers 3, four channels out of 34 multiplexed FM multiplexed signals transmitted from the optical CATV headend 1. Is distributed to each subscriber 3. That is, in the hub 2, the optical multiplexed signal transmitted from the trunk optical fiber cable 4 is supplied to an optical / electrical (O / E) converter 21, converted into an electric signal, and supplied to a four-channel selection circuit 22. . The four-channel selection circuit 22 selects a four-channel television signal from the thirty-four-channel television signal according to a control signal provided from the local control circuit 23. The selected four-channel television signal is converted into an optical signal by the E / O converter 24 and transmitted to each subscriber 3 via the optical fiber 5 through the optical combiner 26.

In the subscriber 3, the optical signal is converted into an electric signal for each channel by the O / E converter 32 via the optical combiner 31, and the television signal of each channel is received by the BS tuner 33. When a command for selecting any of the BS channels is given by the channel selection remote controller 34, a channel selection signal is given from the BS tuner 33 to the encoder 35. Channel selection signals supplied from the four BS tuners 33 are multiplexed by an encoder 35, converted into optical signals by an E / O converter 36, and transmitted through an optical combiner 31, a subscriber optical fiber cable 5, and an optical combiner 26. O / E converter 2
After being given to 5 and converted into an electric signal, it is given to the local control circuit 23. The local control circuit 23 supplies a control signal corresponding to the channel selection signal to the four-channel selection circuit 22. The four-channel selection circuit 22 selects a television signal of a desired channel according to the control signal.

6 and 7 are diagrams showing examples of connection between the four BS tuners shown in FIG. 5 and encoders.

The four BS tuners 33a, 33b, 33c and 3 shown in FIG.
When the 3d and the encoder 35 are connected, as shown in FIG. 6, a method of connecting each of the BS tuners 33a to 33d and the encoder 35 in a bus format, and as shown in FIG.
There is a star connection method in which a to 33d and the encoder 35 are individually connected.

[Problems to be Solved by the Invention] By the way, for example, four BS tuners 33a
When installing ~ 33d, for example, one is installed in the living room,
One may be installed in the same living room for recording the back program, and the other BS tuner may be installed in the children's room. In such a case, in the bus connection method shown in FIG. 6, the wiring of the cable becomes long depending on the place where the encoder 35 is installed, and in the star connection shown in FIG. Need to be wired to the encoder 35, resulting in wasteful wiring.

Moreover, the channel selection signals output from the BS tuners 33a to 33d are multiplexed by the encoder 35 and
However, if the channel selection signals are output simultaneously from each of the BS tuners 33a to 33d when they are connected in a bus shape as shown in FIG. It is impossible to determine whether the channel selection signal has been output from the BS tuner.

Further, in the example shown in FIG.
It suffices to terminate at 33d, but in the example shown in FIG. 7, it is necessary to terminate at each of the BS tuners 33a to 33d, and the method of termination differs depending on the connection method. .

Therefore, a main object of the present invention is to provide a bus connection system, a star connection system, and a CATV reception system which can easily connect a BS tuner to an encoder without causing a conflict in a channel selection signal even when both are mixed. The purpose is to provide a bus control device for the machine.

Means for Solving the Problems The present invention relates to a CATV receiver including a plurality of receivers and an encoder which receives a channel selection signal output from each receiver via a bus and outputs the signal to a transmission side. Bus control device for controlling each of the receivers, prohibiting each receiver from outputting its own channel selection signal in response to determining that one of the other receivers is outputting the channel selection signal. And a control unit that outputs its own channel selection signal in response to determining that none of the other receivers has output a channel selection signal.

Each encoder is provided corresponding to each of the receivers, and receives input / output means for receiving a channel selection signal sent from the corresponding receiver, and outputs a channel selection signal sent from one of the input / output means. The gate means for outputting to the transmitting side, and one of the input / output means determines that the channel selection signal has been received, and the input / output means other than the input / output means which has received the channel selection signal sends the other buses to the respective buses. Output control means for outputting a signal indicating that the bus is outputting a channel selection signal.

[Operation] The bus control device of the CATV receiver according to the present invention, when a channel selection signal is output from any one of the receivers, detects the channel selection signal with the encoder, and outputs the channel selection signal from another receiver. A signal indicating that the signal has been output is output to the bus, and the other receivers are inhibited from outputting the channel selection signal by the signal, so that the channel selection signal does not conflict. Therefore, even if each receiver and encoder are connected in a bus-like connection system, a star-like connection system, or both, the encoder can easily determine that the channel selection signal has been output from any of the receivers.

[Embodiment of the Invention] Fig. 1 is a diagram showing an example in which four BS tuners and encoders are connected in a mixture of a bus shape and a star shape using one embodiment of the present invention. In FIG. 1, the BS tuners 33a and 33b are connected to the encoder 35 in a bus shape, and the BS tuners 33c and 33d are connected to the encoder 35 in a star shape.

FIG. 2 is a schematic block diagram of a BS tuner in one embodiment of the present invention, and FIG. 3 is a block diagram of an encoder and an I / O control circuit.

The BS tuner 33 receives the signal from the O / E converter 32 shown in FIG.
An F signal is provided, and this RF signal is mixed with a local oscillation signal output from a local oscillator 333 by a mixer 332 included in a tuning unit 331, and an intermediate frequency signal is output. This intermediate frequency signal is provided to a demodulator 335 via a filter 334 and demodulated into a video signal.

In the example shown in FIG. 5, one of the 34 channel television signals can be selected. In this embodiment, however, any one channel television signal can be selected from the 40 channel television signals. Can be selected.
The selection of one channel television signal from the 40 channel television signals is performed by a channel selection remote controller 34 provided corresponding to the BS tuner 33. The channel selection signal from the channel selection remote controller 34 is received by the remote controller reception circuit 336 and is given to the CPU 337. CPU33
7 is the selection signal decoding circuit 338 and the channel display control circuit 339 and I
/ O control circuit 340. The selection signal decoding circuit 338 decodes the selection signal and supplies it to the I / O control circuit 340 and also to the channel display control circuit 339 to cause the display 341 to display the selected channel number. The channel selection signal is also supplied to the local oscillator 333, and a local oscillation signal corresponding to the selected channel number is supplied to the mixer 332.

The I / O interface circuit 36 is connected to the I / O control circuit 340. The interface circuit 36 includes a driver 37, a receiver 38, and resistors R1 to R4. The driver 37 outputs the channel selection signal output from the I / O control circuit 340 to the encoder 35.
Output to The receiver 38 supplies a channel selection signal output from another BS tuner to the CPU 337. When a channel selection signal is given from another BS tuner via the receiver 38, the CPU 337 temporarily puts the driver 37 in a standby state, prohibits the output of the channel selection signal to the encoder 35, and prevents the channel selection signals from conflicting with each other. To control.

A resistor R1 is connected between the input side of the receiver 38 and the power supply, resistors R2 and R3 are connected in series between the input of the receiver 38 and the bus, and a resistor R4 is connected between the input side and the ground. You.
These resistors R1 to R4 change the output of the driver 37 to "L" level when the bus is in a high impedance state, and are selected to be negligible when the bus is active.

Next, referring to FIG. 3, on the input side of the concoder 35, interface circuits 39a to 39d are provided corresponding to the respective BS tuners 33a to 33d.
Connected to BS tuners 33a-33d. Interface circuit
39a is configured similarly to the interface circuit 36 of the BS tuner 33 shown in FIG.
And resistors R1 to R4. However, the input end of the driver 41a is grounded, and a terminating resistor Rm is connected between the two inputs of the receiver 40a. The terminating resistor Rm is for impedance matching of the bus, and is generally selected to have a value of about 100Ω.

The encoder 35 has output enable controllers 41a to 41d corresponding to the respective BS tuners 33a to 33d.
Is provided. The output enable controllers 41a to 41d have input terminals 0 to 3 corresponding to the four BS tuners 33a to 33d, respectively.
3, the input terminal of the corresponding BS tuner is grounded.

The output of the interface circuit 39a is connected to the input terminals 0 of the output enable controllers 41b, 41c, 41d, and is also connected to one input terminals of the input detection circuit 43 and the OR circuit 44. The output of the interface circuit 39b is connected to the input terminal 1 of the output enable controller 41a, 41c, 41d, and is also connected to one input terminal of the input detection circuit 43 and one input terminal of the OR circuit 44. The output of the interface circuit 39c is connected to the input terminal 2 of the output enable controllers 41a, 41b, 41d, and is also connected to one input terminal of the input detection circuit 43 and one input terminal of the OR circuit 44. Interface circuit
39d output is output enable controller 41a, 4
1b, 41c connected to the input terminal 3 and an input detection circuit
43 and one input terminal of the OR circuit 44.

The output enable controller 42a controls a driver 41a of the interface circuit 39a, and the output enable controllers 42b to 42d are provided for controlling drivers of other interface circuits 39b to 39d. That is, the output enable controllers 42a to 42d
When a channel selection signal is input to any of the interface circuits 39a to 39d, a signal indicating that the bus can be used for an interface circuit other than the input interface circuit is output. In the example shown in FIG. 3, the bus is "L".
Even when the level is active, the interface circuit to which the channel selection signal is input is also output an "L" level signal to other interface circuits even when the interface circuit is at the "L" level. When the bus is in a high impedance state.

The output of the receiver 38 of the BS tuner 33 shown in FIG.
When the bus is at “L” level, it goes to “H” level,
Since the "L" level signal is output at the time of the level and the high impedance, if the output of the receiver 38 is at the "H" level, that is, the bus is at the "L" level, it is determined that the bus is in an active state. Then, transmission of the channel selection signal is temporarily waited, and after waiting for the bus to be free, the channel selection signal is transmitted. When the output to the receiver 38 is at the “L” level, it cannot be determined whether the bus is in the active state at the “H” level or high impedance (non-active state). Therefore, the output of the "H" level and the output of the "L" level are repeated in the above pattern, so that the BS tuner 33 can determine the state of the bus based on the state.

FIG. 4 is a timing chart for explaining the operation of one embodiment of the present invention.

Next, a specific operation of one embodiment of the present invention will be described with reference to FIGS. Here, it is assumed that a channel selection signal has previously been output from the BS tuner 33c and input to the interface circuit 39c, and the inputs of the interface circuits 39a to 39d are currently in a high impedance state. At this time, the output enable controllers 42a to 42d have been switched to the input terminal 2. Therefore, the output of the interface circuits 39a to 39d, the output of the input detection circuit 43, and the output of the output enable controllers 42a to 42d are in the state of the time chart shown in FIG.

Next, for example, when an “L” level signal is output from the BS tuner 33a, the interface circuit 39 of the encoder 35
The output of the driver 40a of "a" becomes "H" level. When the input detection circuit 43 detects that an input has been made to the interface circuit 39a, the output enable controllers 42a to 42a-4
2d is switched to the input terminal 0 side. Since the input terminal 0 of the output enable controller 42a is grounded, an "L" level control signal is supplied to the driver 41a of the interface circuit 39a. Therefore, the output of the driver 41a enters a high impedance state.

On the other hand, output enable controllers 42b to 42d
Are switched to the input terminal 0 side, and the output of the receiver 40a of the interface circuit 33a is
39b-39d. While the output of the receiver 40a of the interface circuit 39a is at the “H” level, the enable signal is output to each of the output enable controllers 42b, 42c and 42d.
To the respective drivers of the interface circuits 39b, 39c and 39d, and brought into an active state. Since the input of the driver of each of the interface circuits 39b, 39c and 39d is grounded, an "L" level signal is output to the bus as shown in the timing of FIG. 4, and the bus becomes active.

Next, when an “H” level signal is input to the interface circuit 39a, the output enable controller 42b
The outputs of .about.42d go to "L" level, and as shown in the timing of FIG. 4, the inputs of the drivers of the interface circuits 39b to 39d become high impedance. By repeating this, the BS tuner 3 corresponding to the interface circuit 39a is
When the output of the channel selection signal from 3a is completed, as shown in the timing of FIG.
.About.39d are in a high impedance state, and this state is maintained until the next output from the BS tuner.

As described above, according to this embodiment, the BS tuner 33a
When a channel selection signal is output from any one of ~ 33d, the encoder 35 detects this channel selection signal, outputs a signal indicating that the channel selection signal has been output from another BS tuner to the bus, and outputs Since the BS tuner inhibits the output of the channel selection signal based on the signal, the channel selection signals do not compete with each other.

Moreover, each interface circuit 39a to 3 of the encoder 35
Since the terminating resistor Rm is connected to each bus input side of 9d, no reflection occurs even if the distance between the BS tuners 33a to 33d and the encoder 35 is long. Further, even if the connection is made in a star shape or a bus shape, it is not necessary to change the mounting position of the terminating resistor Rm each time. That is, in the example shown in FIG. 1, the BS tuners 33a and 33b connected in a bus shape are terminated at the input end 5a of the encoder 5, and are respectively connected to the BS tuners 33c and 33d connected in a star shape. On the other hand, they are individually terminated at the input terminals 5c and 5d of the encoder 5.

[Effects of the Invention] As described above, according to the present invention, each receiver inhibits output of its own channel selection signal if any of the other receivers outputs a channel selection signal, If the other receiver does not output the channel selection signal, output its own channel selection signal, and the encoder supports other receivers if the channel selection signal is output from any receiver Since a signal indicating that the channel selection signal is being output is output from the input means to each bus, it is possible to prevent the channel selection signals from competing with each other.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example in which four BS tuners and encoders are connected in a mixture of a bus shape and a star shape using one embodiment of the present invention. FIG. 2 is a schematic block diagram of a BS tuner according to one embodiment of the present invention. FIG. 3 is a schematic block diagram of an encoder. FIG. 4 is a timing chart for explaining the operation of one embodiment of the present invention. FIG. 5 is a schematic block diagram showing the overall configuration of an optical CATV system to which the present invention is applied. 6 and 7 are diagrams showing examples of connection between the four BS tuners shown in FIG. 5 and encoders. In the figure, 33a to 33d are BS tuners, 35 is an encoder,
36, 39a to 39d are interface circuits, 37 and 41a are drivers, 38 and 40a are receivers, 42a to 42d are output enable controllers, 43 is an input detection circuit, 44 is an OR circuit, 33
7 denotes a CPU, 338 denotes a selection signal decoding circuit, and 340 denotes an I / O control circuit.

Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 7/16 H04B 9/00 C (72) Inventor Mikio Maeda 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside Japan Broadcasting Corporation Broadcasting Research Institute ( 72) Inventor Kazumi Utsumi 1-10-11 Kinuta, Setagaya-ku, Tokyo Inside the Japan Broadcasting Corporation Research Institute of Broadcasting Technology (58) Field surveyed (Int. Cl. ⁶ , DB name) H04N 7/10, 7/14- 7 / 173,7 / 20-7/22

Claims (1)

(57) [Claims] 1. A bus control device for controlling a bus in a CATV receiver including a plurality of receivers and an encoder which receives a channel selection signal output from each receiver via a bus and outputs the signal to a transmission side. In each of the receivers, in response to determining that any of the other receivers is outputting a channel selection signal, prohibits outputting its own channel selection signal, In response to determining that none of the receivers output a channel selection signal, the receiver includes control means for outputting its own channel selection signal, and the encoder is provided corresponding to each of the receivers Input / output means for receiving a channel selection signal sent from a corresponding receiver, a gate means for outputting a channel selection signal sent from any of the input / output means to the transmission side, And determining that any one of the input / output means has received the channel selection signal. A bus control device for a CATV receiver, comprising: output control means for outputting a signal indicating that a selection signal is being output.