JPH0531993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Field of Industrial Application" The present invention is useful in the case where, for example, a plurality of AV devices are connected in one building by one transmission line, The channel is detected, the modulation frequency of the AV signal is set to the empty channel, and the channel number etc. is transmitted in the baseband through the above-mentioned one transmission line, and the receiving side decodes the self-address information and selects the specific channel. The present invention relates to a home bus device that allows for channel selection and mutual transmission and reception of signals between devices.

``Conventional technology'' Conventional home bus systems include a method that uses power lines to control TV receivers, air conditioners, etc. in each room, and a standardized method for using a home bus within a building or local area. It was hot.

``Problems to be solved by the invention'' Methods using power lines only turn devices on and off, and transmission of AV signals was either impossible or extremely difficult. Furthermore, although it is possible to transmit AV signals using a method based on home bus standardization, there are problems in terms of economy.

"Means for Solving the Problems" The present invention was made in order to solve the problems mentioned above. In a device coupled by a transmission line, there is a means for detecting an empty channel in a TV broadcast wave band, a modulation frequency of an AV signal is set in the empty channel by the empty channel detection means, and a channel of the selected empty channel is set. A transmission means that superimposes a number or a number corresponding to the number as self-address information on the transmission line at the baseband, and a receiver side that decodes the self-address information from this transmission means.
and a means for causing the PLL tuner to select a designated channel.

"Operation" PLL sweep is performed on the transmitting side of FM/TV broadcast wave receiving antennas and mixers, and certain AV equipment.
Search each channel one by one and determine unused tuning frequencies using the beat method. Digital data is transmitted using the baseband using the determined conversion channel number as self-address information. Since the receiving side of the other AV equipment is equipped with a PLL channeler, processing is performed when the other party's address matches its own address. In this way, an empty channel is detected and a transmission channel is determined, so that AV signals can be transmitted without the need for a special tuner.

"Example" An embodiment of the present invention will be described below.

1 is an antenna and mixer for receiving FM/TV broadcast waves, and a transmission line 2 made of a coaxial cable is coupled to this antenna and mixer 1. Specifically, this transmission line 2 has a maximum length of 200 m, and has multiple tap-offs 3a for signal branching along the way...
VA devices 4a...4n are coupled via 3n.

The antenna and mixer 1 and each of the AV devices 4a...4n include means for detecting an empty channel in the TV broadcast wave band, and setting the modulation frequency of the AV signal in the empty channel by the empty channel detection means. The transmission line 2 uses the channel number of the empty channel or the number corresponding thereto as self-address information in the baseband.
and a transmission means superimposed on the. Further, the AV equipment 4a...4n includes a monitor TV, a tuner,
The device may be any device such as a door camera or a VTR, but it is equipped with at least a means for decoding the self-address information from the transmission means and causing the internal PLL channel to select a designated channel, and specifically, for communication control. It includes an IFU 5, a logic circuit section 6, a modulator/demodulator 7, and an AV signal processing section 8.

Next, the operation of the above configuration will be explained.
The transmission line 2 is a single coaxial cable, and devices 4a...4n having distributed processing functions are connected to this to form a bus system. Also, home bus 2
The control signals of the devices 4a...4n connected to the terminal and the various information signals handled are frequency division multiplexed as shown in FIG. The baseband region up to 10MHz is allocated to bidirectional transmission paths for control signals and low-speed information, and the broadband region above 10MHz is used for the transmission of high-speed data, analog information, and video signals, as well as the FM band suitable for home communal listening systems. and TV broadcasting bands will be allocated.

The control signal is transmitted to bus 2 by the bucket communication method.
It is bidirectionally transmitted between the devices 4a...4n connected to the
Multiple Access with Collision Detection) access control method is adopted.

A specific transmission waveform of the control signal transmitted in the baseband region is shown in FIG. Each device 4a...
The 4n control signal transmission circuit is connected to bus 2, which is connected to the power supply via a resistor, in an open collector format using wired AND (sometimes called wired OR, but since it is a positive AND logic, it is wired).
AND) is connected, and the transmission speed is 9600 bits/
Transmits a 5V amplitude NRZ signal with positive logic. Therefore, direct current and alternating current power supplies are not superimposed (power fed) on the bus, and logic "0" of the control signal on the bus can be transmitted preferentially over logic "1".

As mentioned above, the access control method is CSMA/
A CD is adopted, and the logic "0" on the bus 2 is monitored as a carrier, and if the carrier is not detected for a certain period of time (11 bit time), signal transmission is started. Even if multiple devices 4a...4n start transmitting to the bus at almost the same time, logic "0" takes priority on the bus, so they have to compare their own transmitted signals and the received signals from the bus bit by bit. Therefore, collisions on the bus can be detected. Since a device that detects a collision immediately shifts to receiving operation, only one device with a high priority can transmit until the end. After the transmission is completed, the device that interrupted transmission due to collision detection retransmits after confirming that no carrier detection is performed for a certain period of time.

As shown in FIG. 3, the synchronization method and bucket configuration are a start-stop synchronization method in units of 8 bits per byte. The transmitting side transmits 2 stop bits, and the receiving side recognizes up to 1 stop bit.
The remaining 1 bit time is allocated to internal processing time. A bucket is constructed using this 1-byte transmission as a basic unit, and the bucket format as shown in FIG. 4 is adopted as a whole. The first part of the bucket is the address of the device to send (self address), followed by the address of the device to receive (destination address), control code, data length, data up to 256 bytes, and frame check for error detection.・Continued with code. Device addresses are normally 8 bits, but can be extended to 16 bits by considering a single byte following a specific address as an address.

Error detection on the receiving side is performed using a byte-by-byte validity bit and a frame check code. Even-numbered validity is added to the validity bit, and the frame check code is a two's complement of the sum from the self address to the final byte of data, and a checksum error detection method is adopted.
If a response request is specified in the control code on the transmitting side, depending on the error detection result on the receiving side,
A 1-byte response code, ACK or NAK, is returned within 4 to 8 bits after the previous packet has been received. The sending side determines that the bucket transmission is complete only when it receives an ACK response code, but if it receives a NAK code or receives no response, it retransmits the required number of times.

The bucket priority is determined by the bucket transmission interval and
Two types of self-addresses are specified. The bucket transmission interval is 11+N (N=0, 1, 2, 3) bit times and determines four levels of priority. The priority order of buckets at the same level is determined by the first byte of the bucket, that is, the self address of the device sending the bucket. Specifically, a bucket message transmitted from a device with a self-address 00 having a bucket transmission interval of N=0 has the highest priority.

As shown in Figure 2, in addition to the existing FM bands and TV broadcast bands being allocated as is, transmission channels for high-speed data, audio signals, and video signals will be provided within subbands from 10MHz to 75MHz. The reason why all frequency bands are not allocated is to avoid interference from other devices such as amateur radios and interference with other home devices such as TV intermediate frequencies.

Digital data is transmitted and received as described above, but in order to detect an empty channel according to the present invention, the transmission side of the AV equipment 4a...4n performs a PLL sweep, searches each channel one by one, and selects an unused channel frequency. Determined by beat method. Digital data is transmitted using the baseband using the determined conversion channel number as self-address information. Other AVs
Since the receiving side of the devices 4a...4n is equipped with a PLL tuner, processing is performed when the other party's address matches its own address. In this way,
Since the transmission channel is determined by detecting an empty channel, AV can be used without the need for a special tuner.
A signal is transmitted.

"Effects of the Invention" Since the present invention is configured as described above, each AV device can easily detect an empty channel and determine a transmission channel. Therefore, if the receiving side is equipped with a PLL tuner that is already prepared for TV reception, a large number of AV signals can be transmitted without the need for a special tuner.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the home bus device according to the present invention, Fig. 2 is an explanatory diagram of frequency allocation, Fig. 3 is a transmission waveform diagram of control signals, and Fig. 4 is a packet flow diagram of digital data. It's Matsuto. 1...FM/TV broadcast wave receiving antenna and mixer, 2...1 transmission line (coaxial cable), 3a to 3m...dap-off for signal branching, 4
a~4n...AV equipment, 5...Communication control IFU, 6
...Logic circuit section, 7...Modulator/demodulator, 8...AV signal processing section.

Claims (1)

[Claims] 1. Means for detecting an empty channel in the TV broadcast wave band in a device in which an FM/TV broadcast wave receiving antenna and mixer are coupled with a plurality of AV devices via a single transmission line, and a method for detecting the empty channel. a transmission means for setting a modulation frequency of an AV signal on an empty channel by a means, and superimposing a channel number of the selected empty channel or a number corresponding thereto on the transmission line at baseband as self-address information; 1. A home bus device comprising means for decoding self-address information from a receiver and causing a receiving side PLL tuner to tune to a specified channel.