JPH04332275A - Channel selecter for television - Google Patents

Abstract

PURPOSE:To operate a channel selection in an almost as short time as convention, and to reduce the data amount to be stored. CONSTITUTION:As for the channel selecter of a television, equipped with a microcomputer 10 which operates an AFT operation based on the reference PLL data of a selected channel, and a tuner 2 which takes out a desired channel selection signal based on the PLL data of this microcomputer 10, plural reference offset data to which a mode number is added are prepared, the mode number of the reference offset data closest to the offset data at the time of the just tuning of each channel is stored, the mode number of the selected channel is read out at the time of channel selection, the reference offset data of this mode number are added to the reference PLL data, and the data are outputted.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television channel selection device using a PLL (phase locked loop) frequency synthesizer system.

0002

2. Description of the Related Art In a PLL frequency synthesizer system, an AFT (automatic frequency tuning) operation is performed so that even a signal offset from a regular frequency can be tuned. This AFT operation takes time (1 to 2 seconds) in proportion to the magnitude of the offset amount, and the tuning time is much longer than when receiving a signal without offset.

[0003] Conventionally, therefore, the offset amount for each channel is stored in a memory, and when a channel is selected, PLL data with the stored offset amount taken into account is output to the tuner to shorten the tuning time. I'm trying.

0004

However, the conventional configuration has the disadvantage that the amount of data is large and a large capacity memory is required because the offset amount for each channel is stored.

For example, in order to be able to receive up to a ±2.0 MHZ offset signal with respect to a regular signal, if the resolution of the tuner (PLL) is 31.25 KHZ, there will be 128 steps, and 8 bits of data per channel. is necessary. If all channels 1 to 63 in Japan have this data, 63 bytes will be required. This is 1/2 or 1/2 of the normally used non-volatile memory capacity of 128 bytes or 256 bytes.
This amount corresponds to 4, and the capacity of the nonvolatile memory will be insufficient.

Accordingly, the present invention provides a television channel selection device that can perform channel selection in a time that does not differ significantly from the human senses, although it takes a little longer to select a channel than the conventional one, and which reduces the amount of data to be stored. The task is to do so.

[0007]

[Means for Solving the Problems] To achieve the above-mentioned problems, a television channel selection device according to the present invention includes a channel selection section capable of selecting a channel and outputting selected channel data, and a channel selection section corresponding to each channel data. Standard PLL
A tuning control unit that calculates data and performs automatic frequency tuning by outputting PLL data obtained by adding offset data to reference PLL data when not performing just tuning, and a PL that varies the oscillation frequency based on the PLL data.
In a TV channel selection device having an L circuit and a tuner that uses the output of this PLL circuit as a local oscillation signal and mixes it with a received signal to extract a channel selection signal, a plurality of reference offset data with mode numbers are stored. and a mode number memory that stores the mode number of the reference offset data that is closest to the offset data at the time of just tuning of each channel, and the channel data is output from the channel selection section. and the channel selection control unit reads the mode number of this channel from the mode number memory, reads reference offset data of the read mode number from the reference offset data memory, and adds the read reference offset data to the reference PLL data. This value is output as PLL data to perform an automatic frequency tuning operation.

[0008]

[Operation] When an arbitrary channel is selected in the channel selection section, the tuning control section outputs PLL data in which reference offset data is added to the reference PLL data of the selected channel to the tuner's PLL circuit, and the tuner's tuning signal is Since the automatic frequency tuning operation is performed from a nearby point, it does not take much time to select a station, and the reference offset data memory stores several pieces of reference offset data, and the mode number memory stores the mode number for each channel. The amount of data to be stored is small because all you need to do is

[0009]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. An embodiment of the present invention is shown in FIGS. 1-4.

FIG. 1 shows a circuit block diagram of the main parts of a television. In FIG. 1, an antenna 1 receives a VHF band or UHF band signal, and this received signal is supplied to a tuner 2.

The tuner 2 includes a mixer that mixes a local oscillation signal with a received signal to extract a signal of a desired frequency, and a PLL (phase locked loop) circuit 3 that generates the local oscillation signal. The PLL circuit 3 varies the frequency of the local oscillation signal by varying the PLL data applied to its variable frequency divider.

The intermediate frequency signal output from the tuner 2 is guided to an intermediate frequency processing section 4, where it is subjected to processing such as amplification and detection. The output of the intermediate frequency processing section 4 is guided to the CRT 6 via the amplification section 5. Further, the V synchronization signal and the H synchronization signal are separated in the synchronization separation circuit 7, and the deflection circuit 8 varies the deflection current based on these signals.

On the other hand, the operation section 9 is provided with a channel selection section. The channel selection section is configured to be able to select channels from 1ch to 64ch, and the selected channel data is output to the microcomputer 10.

The microcomputer 10 has a channel selection control section, and when channel data is outputted, it calculates reference PLL data corresponding to this channel data.

Further, the microcomputer 10 has a built-in reference offset data memory 11, and this reference offset data memory 11 stores five types of reference offset data to which mode numbers are assigned.

As shown in FIG. 2, assuming that a signal of frequency f0 can be extracted using the reference PLL data, the reference offset data of mode number 1 is designed to extract a signal shifted by -0.2 MHZ with respect to frequency f0. It is set. The reference offset data for mode numbers 2 to 5 are also set to extract signals shifted by the values shown in FIG. 2, respectively.

Furthermore, the microcomputer 10 controls reading and writing of the mode number memory 12. The mode number memory 12 is a non-volatile memory with a data width of 8 bits.
It has a capacity of This mode number memory 12 stores information such as the mode number for each channel data, and as shown in FIG. The lower 4 bits of the address and odd numbered channel data are stored in the upper 4 bits of the address.

The data to be stored has the meaning shown in the table below. For example, if the mode number of 1ch is 1, data "1" is stored in the upper 4 bits of memory address "00".

[0019]

[Table 1]

The microcomputer 10 also includes an intermediate frequency processing section 4.
The AFT signal of the synchronization separation circuit 7 and the H synchronization signal of the synchronization separation circuit 7 are guided, and when the state of these signals is detected and just tuning is not performed, an automatic frequency tuning (AFT) operation is performed.

FIG. 4 shows a flowchart executed by the microcomputer 10, and the operation will be explained with reference to this flowchart.

When a desired channel is selected using the channel selection section of the operation section 9, the selected channel data is output to the microcomputer 10. The microcomputer 10 calculates reference PLL data corresponding to this channel data and reads out the mode number of the channel data from the mode number memory 12.

[0023] At the time of the first channel selection, data of "F" is stored in the mode number memory 12, so in this case, the reference offset data of mode number 1 is added to the reference PLL data. The value is output to the tuner 2 as PLL data to execute the AFT operation. This AFT
If the just tuning by operation is within a certain period of time, there is a channel selection signal near the point based on this PLL data, so data "1" indicating this mode number 1 is written in the storage area of the corresponding channel data of the mode number memory 12.

In addition, with reference offset data for mode number 1, if just tuning is not done within a certain time, the mode number will be incremented and AFT operation will be performed, and if just tuning is done within a certain time, the mode number will be displayed in the same way as above. Writes data, and in all cases, if just tuning is not done within a certain time, "F" is written.

On the other hand, since the mode number memory 12 generally stores data "1" to "5" during the second and subsequent channel selections, in this case, the mode number "1" read out in the reference PLL data is The value obtained by adding the reference offset data of ``1'' to ``5'' is output to the tuner 2 as PLL data to execute the AFT operation.

[0026] Since the point based on this PLL data is near the tuning signal, just tuning can be performed in a short time (within about 0.4 seconds).

That is, according to this embodiment, although it takes some time for the first channel selection, the time for second and subsequent channel selections is greatly reduced. Moreover, conventionally, 8
However, in this embodiment, the width is 4 bits, which is half of that width, so the amount of stored data is half.

In this embodiment, 5 pieces of reference offset data are used, so 3-bit width is sufficient for each channel, but 3-bit width is difficult to process as data for the microcomputer 10, so 4-bit width data is used. . 16 states can be expressed with 4-bit width data, so if it is not set, 1
If the state is used, a maximum of 15 pieces of reference offset data can be used.

[0029]

As described above, according to the present invention, the channel selection unit and the reference PLL of the selected channel data
TV channel selection equipped with a tuning control section that performs automatic frequency tuning operation based on data, and a tuner that varies the frequency of a local oscillation signal to extract a desired tuning signal based on the PLL data of the tuning control section. The device prepares a plurality of reference offset data with mode numbers, stores the mode number of the reference offset data that is closest to the offset data during just tuning of each channel, and stores the mode number of the selected channel when selecting a channel. Since the automatic frequency tuning operation is performed by reading out the standard offset data of this mode number in addition to the standard PLL data and performing the automatic frequency tuning operation, the tuning time is short and the standard offset data is Since it is only necessary to store the data and the mode number for each channel, the amount of stored data can be reduced.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram of the main parts of a television (embodiment).

FIG. 2 is a diagram (example) showing the shift amount of each reference offset data with respect to the normal frequency (f0).

FIG. 3 is a diagram (embodiment) showing memory addresses and their data contents in a mode number memory.

FIG. 4 is a flowchart diagram (example).

[Explanation of symbols]

2...Tuner, 3...PLL circuit, 9...Operation section (channel selection section), 10...Microcomputer (channel selection control section), 11...Reference offset data memory, 12...Mode number memory.

Claims (1)

[Claims] 1. A channel selector that can select a channel and outputs selected channel data, and a PLL that calculates reference PLL data corresponding to each channel data and adds offset data to the reference PLL data when not performing just tuning. It has a tuning control section that outputs data and performs an automatic frequency tuning operation, and a PLL circuit that varies the oscillation frequency based on the PLL data, and uses the output of this PLL circuit as a local oscillation signal and mixes it with the received signal for selection. In a television channel selection device equipped with a tuner for extracting station signals, a reference offset data memory stores a plurality of reference offset data with mode numbers attached;
and a mode number memory that stores the mode number of the reference offset data that is closest to the offset data at the time of just tuning of each channel, and when the channel data is output from the channel selection section, the channel selection control section The mode number of this channel is read from the mode number memory, the reference offset data of this read mode number is read from the reference offset data memory, and the value obtained by adding this read reference offset data to the reference PLL data is output as PLL data. A television channel selection device characterized in that it performs an automatic frequency tuning operation.