JPH0438091A - Channel selection signal contention controller for catv receiver - Google Patents

Abstract

PURPOSE:To prevent the contention of selection signals by transmitting a channel selection signal while turning a bus to a using state after passing time adding different discrimination numbers set in respective receivers and a waiting time set in advance when the bus is decided in an idle state. CONSTITUTION:A CPU 337 applies a control signal to a driver 37 from an I/O control circuit 340, and the bus is turned to be high impedance by the driver 37. The CPU 337 decides whether the channel selection signal is transmitted or not, waits when the channel selection signal is not transmitted, and sets the time of (T+nt) to a timer when to be transmitted. When a BS tuner 33a completes the transmission of the channel selection signal and the bus becomes a non-active state, the CPU 337 decides whether the timer firaishes counting of the time of (T+nt) or not, decides the state of the bus again when it is not finished, and transmits the channel selection signal to turn the bus to high impedance when the timer finishes counting the time of (T+nt).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a channel selection signal contention control device for a CATV receiver, and more particularly, to a channel selection signal contention control device for a CATV receiver, and more particularly, to a channel selection signal contention control device for controlling a channel selection signal contention at a hub from a multi-channel optical multiplexed television signal transmitted from a CATV head end. In a CATV system in which a TV signal of a channel is selected and distributed to each subscriber's BS tuner, and a channel selection signal from the BS tuner is transmitted from an encoder to a hub via a bus, the signal that is output from each BS tuner to the encoder is CAT such as controlling contention of channel selection signals
The present invention relates to a channel selection signal contention control device for a V receiver.

[Prior Art] In urban CATV including independent broadcasting and two-way transmission, there is a strong demand for multi-channel video signals and higher quality. Furthermore, recently, optical fibers, which have superior characteristics such as broadband, low loss, and non-dielectric properties, have been increasingly used as transmission media compared to coaxial cables.

As an example of CATV that uses optical fiber as a transmission medium, an FM multiplex high-definition optical CATV system using a demand access method (IEICE Research Report 0C8)
89-51, pages 7 to 12, 1989).

FIG. 6 is a schematic block diagram showing the overall configuration of the above-mentioned proposed optical CATV system. In FIG. 6, the optical CATV system is composed of an optical CATV head end 1, a hub 2, and a subscriber 3. The CATV headend 1 is installed at a CATV broadcasting station, where 34 channels of TV signals from cameras, VTRs, etc., which are the sources of MUSE signals, are converted to FM using an FM modulator at different carrier frequencies.
Modulated and multiplexed into electrical/optical (Elo) converter 12
The signal is converted into an optical signal and transmitted to the hub 2 via the trunk optical fiber cable 4.

The hub 2 is installed on a telephone pole etc. near multiple subscribers 3,
In response to a request from the subscriber 3, four channels of FM multiplexed signals from the 34 channels transmitted from the optical CATV head end 1 are distributed to each subscriber 3. That is, in the hub 2, the optical multiplexed signal transmitted from the trunk optical fiber cable 4 is given to the optical/electrical (0/E) converter 21, converted into an electrical signal, and then sent to the 4-channel selection circuit 2.
given to 2. The 4-channel selection circuit 22 selects 4-channel television signals from among the 34-channel television signals according to a control signal given from the local control circuit 23. The selected 4 channel TV signal is E10
The signal is converted into an optical signal by the converter 24, and transmitted to each subscriber 3 via the optical combiner 26 via the subscriber system optical fiber 5.

At the subscriber 3, the optical signal is converted into an electrical signal for each channel by the O/E converter 32 via the optical combiner 31, and the television signal of each channel is sent to the BS tuner 33.
received by. When a command to select an arbitrary channel among the BS channels is given using the channel selection remote control 34, a channel selection signal is given from the BS tuner 33 to the encoder 35. Channel selection signals given from the four BS tuners 33 are sent to the encoder 3.
5, is converted into an optical signal by an E10 converter 36, and is sent to an optical combiner 31. Subscriber optical fiber cable 5
．． is given to the O/E converter 25 via the photosynthesizer 26,
After being converted into an electrical signal, it is applied to the local control circuit 23. The local control circuit 23 provides the four-channel selection circuit 22 with a control signal corresponding to the channel selection signal.

The 4-channel selection circuit 22 selects a desired channel of television signal according to the control signal.

[Problems to be Solved by the Invention] Incidentally, in the optical CATV system described above, channel selection signals are individually transmitted from the BS tuners 33a to 33d shown in FIG. 6 and given to the encoder 35. When the encoder 35 receives channel selection signals from the BS tuners 33a to 33d at different timings, it can easily determine which BS tuner has transmitted the channel selection signal. However, if the channel selection signals are simultaneously output from the BS tuners 33a to 33d, for example, competition will occur, and the encoder 35 will not be able to determine which BS tuner has transmitted the channel selection signal.

Therefore, in order to avoid such conflicts, either B
When the S tuner is transmitting a channel selection signal, competition control is performed so that channel selection signals are not transmitted from other BS tuners.

FIG. 7 is a timing diagram for explaining competition control of channel selection signals. In FIG. 7, for example, in a state where the BS tuner 33a is outputting a channel selection signal, the BS tuner 33b transmits a channel selection signal at timing ta, and the BS tuner 33b transmits a channel selection signal at timing tb.
Even if an attempt is made to transmit a channel selection signal from the S tuner 33C, since the BS tuner 33a is in the process of transmitting the channel selection signal, the BS tuner 33b, 3
3c is put on standby. After the BS tuner 33a finishes transmitting the channel selection signal and a time period T has elapsed, the standby state of the BS tuners 33a and 33b is released. Then, channel selection signals are transmitted from both the BS tininas 33b and 33c at timing tc, causing a problem in that a conflict condition occurs at this timing.

Therefore, a primary object of the present invention is to control the channel selection of a CATV receiver capable of controlling contention so that when one receiver finishes transmitting a channel selection signal, channel selection signals are not transmitted simultaneously from other receivers. An object of the present invention is to provide a selection signal contention control device.

[Means for Solving the Problems] The present invention provides a CATV receiver including a plurality of receivers and an encoder that receives a channel selection signal output from each receiver via a bus and outputs it to a transmitting side. A channel selection signal contention control device that controls contention of channel selection signals output from receivers, in which each receiver is assigned a different identification number, and is used to determine whether a bus is free or not. a discriminating means for discriminating, and inhibiting output of a channel selection signal in response to the discriminating means determining that the bus is not in an idle state, and inhibiting output of a channel selection signal in response to determining that the bus is in an idle state; and a control means for putting the bus in use and outputting a channel selection signal after the elapse of a time added to a predetermined time.

[Operation] The channel selection signal competition control device for CATV receivers according to the present invention prohibits the output of the channel selection signal when it is determined that the bus is not in an empty state, and if the bus is in an empty state, the output of the channel selection signal is prohibited for each receiver. Since the bus is put into use and the channel selection signal is output after the time that has elapsed is the sum of the identification number specified in , when each receiver outputs a channel selection signal, each receiver applies the channel selection signal after a different amount of time has elapsed, so multiple receivers will not output channel selection signals at the same time and there will be no conflict. do not have.

[Embodiment of the invention] Figure 2 shows an encoder and BS in an embodiment of the invention.
FIG. 3 is a diagram showing a connection state with a tuner.

In the example shown in FIG. 2, for example, three BS tuners 33a, 33b, and 33c are connected to the encoder 35 in the form of a bus. Note that the BS tuners 33a to 33c are not limited to this, and a so-called star connection method may be used in which the BS tuners 33a to 33c are individually connected to the encoder 35.

FIG. 3 is a schematic block diagram of a BS tuner in one embodiment of the present invention.

The BS tuner 33 includes an O/E converter 3 shown in FIG.
The RF multiplied signal is given from 2, and this RF multiplied signal tuning section 33
By the mixer 332 included in the local oscillator 333
The intermediate frequency signal is mixed with the local oscillation signal output from the oscillator, and an intermediate frequency signal is output. This intermediate frequency signal is applied to a demodulator 335 via a filter 334 and demodulated into a video signal.

In addition, in the example shown in FIG. 6, 3-! Although it is possible to select one of the iL channel television signals, in this embodiment, 4C-! - It is assumed that any one channel of TV signals can be selected from the TV signals of Yanel. Selecting one channel of television signals from 40 channels of television signals is performed by a channel selection remote control 34 provided corresponding to the BS tuner 33.

The channel selection signal from the channel selection remote control 34 is received by the remote control reception circuit 336 and sent to the CPU 33.
7 is given. The CPU 337 is the selection signal decoding circuit 33
8, channel display control circuit 339 and I10 control circuit 34
Including 0. The selection signal decoding circuit 338 decodes the selection signal and supplies it to the I10 control circuit 340 as well as to 33 channel display control circuits to display the selected channel number on the display 341. The channel selection signal is also given to the local oscillator 333, and a local oscillation signal corresponding to the selected channel number is given to the mixer 332.

An I10 interface circuit 36 is connected to the I10 control circuit 340. 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 I10 control circuit 340 to the encoder 35. Receiver 38
provides the CPU 337 with a channel selection signal output from another BS tuner. When the CPU 337 receives a channel selection signal from another BS tuner via the receiver 38, the CPU 337 puts the driver 37 into a temporary standby state and prohibits outputting the channel selection signal to the encoder 35 to prevent channel selection signals from competing with each other. control.

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

FIG. 4 is a waveform diagram showing an example of a channel selection signal.

In FIG. 4, the channel selection signal can be regarded as one packet containing necessary information, and a header section is provided at the beginning of the packet, followed by an identification number and a request information section. It is provided. The packet shown in FIG. 4 is an example, and its structure can be arbitrary. One packet is a pulse train that can be expressed by two values, an active state and an inactive state of an electrical signal, and the beginning of one packet can be defined as the first time the signal state becomes active, and the end is defined as the time when the signal state becomes active for the last time. It can be defined as when

The longest period during which the signal is inactive from the beginning to the end of one packet is defined as T. This is a unique value once the data structure of the packet is determined.

For example, there is a widely used signal format for infrared remote control called "rNEC format", and in the format of this embodiment, the value of T is set to 4.5m5ec.

FIG. 1 is a flow diagram for explaining the operation of an embodiment of the invention, and FIG. 5 is a timing diagram for explaining competition control in an embodiment of the invention.

Next, with reference to FIGS. 1 to 5, a specific operation of an embodiment of the present invention will be described.

The CPO 337 shown in FIG. 3 provides a control signal from the I10 control circuit 340 to the driver 37, and the driver 37 makes the bus high impedance.

The CPU 337 determines whether or not to transmit a channel selection signal. If the channel selection signal is not to be transmitted, it waits; if it is to be transmitted, it sets a timer of T+nt.

As shown in FIG. 4 above, the time T+nt is the longest period between the start and end of one packet, during which the signal is inactive. n is each BS tuner 3
3a to 33c, for example, rOJ for the BS tuner 33a, rlJ for the BS tuner 33b, and "2" for the BS tuner 33C.
” is determined. t is the time resolution when observing the state of the bus. Note that the timer is a software timer that counts time when the CPU 337 executes a program.

The CPU 337 inputs the bus status, determines whether the bus is active or not, and if it is active, sets the timer to T+nt again and inputs the bus status again.

This operation is repeated until the bus becomes inactive. For example, when the BS tuner 33a finishes transmitting the channel selection signal and the bus becomes inactive, the CPU 337 determines whether the timer has finished counting the time T+nt,
If the timer has not finished counting, the state of the bus is determined again, and if the timer has finished counting the time T0nt, a channel selection signal is transmitted and the bus is set to high impedance.

Therefore, as shown in FIG. 5, for example, while the BS tuner 33a is transmitting the channel selection signal,
S tuner 33b is t'a and BS tuner 33c
When the BS tuners 33b and 33c attempt to transmit channel selection signals at respective timings t'b, the BS tuners 33b and 33c are in a standby state because the bus is in an active state.

When the BS tuner 33a finishes transmitting the channel selection signal, the BS tuner 33b transmits the channel selection signal after a time period of T+t, and the BSS unit 33c attempts to transmit a channel selection signal after a time period of T+2t.
Since the BS tuner 33b has already transmitted the channel selection signal at that time, the BS tuner 33C is again in a standby state, and no contention occurs at timing t'c. After the BS tuner 33b finishes transmitting the channel selection signal, the BS tuner 33C transmits the channel selection signal after a time period of T+2t has elapsed.

[Effects of the Invention] As described above, according to the present invention, when it is determined that a bus is vacant, different identification numbers set for each receiver and a predetermined time are added together. Since the bus is put into use after a certain period of time and the channel selection signal is transmitted, when the receiver finishes transmitting the channel selection signal, there is no risk that other receivers will transmit the channel selection signal at the same time. Conflicts can be prevented.

[Brief explanation of the drawing]

FIG. 1 is a flowchart for explaining the specific operation of an embodiment of the present invention. FIG. 2 is a diagram showing a connection state between an encoder and a BS tuner in an embodiment of the present invention. FIG. 3 is a schematic block diagram of a BS tuner in one embodiment of the present invention. FIG. 4 is a waveform diagram showing an example of a channel selection signal. FIG. 5 is a timing diagram for explaining a race condition in an embodiment of the present invention. FIG. 6 is a schematic block diagram showing the overall configuration of an optical CATV system to which the present invention is applied. FIG. 7 is a timing diagram for explaining the contention state of channel selection signals in the optical CATV system shown in FIG. 6. In the figure, 1 is an optical CATV head end, 2 is a hub,
3 is a subscriber, 33a to 33C are BS tuners, 35 is an encoder, 36 is an interface, 37 is a driver, 3
8 is a receiver, 337 is a CPU, and 340 is an I10 control circuit. Figure 1

Claims (1)

[Claims] In a CATV receiver including a plurality of receivers and an encoder that receives a channel selection signal output from each receiver via a bus and outputs it to the transmitting side, A channel selection signal contention control device for controlling contention of channel selection signals, wherein each of the receivers is assigned a different identification number, and a determining means for determining whether or not the bus is in an idle state. ,
and inhibits the output of the channel selection signal in response to the determining means determining that the bus is not in an idle state, and in response to determining that the bus is in an idle state, in response to determining that the bus is in an idle state, A CATV, comprising a control means for putting the bus into use after a time obtained by adding the number and a predetermined time has elapsed, and outputting the channel selection signal.
Receiver channel selection signal contention control device.