NL9500100A - Tuning circuit - Google Patents

Abstract

Circuit device for tuning to a television signal from a number of radio signals which can be received on a television receiver, connected to a display device, provided with a processing unit, and means for feeding coded input data to the processing unit. The circuit device has a character-generating device which is controlled by the processing unit and is connected to the display device in order to generate and display α-numeric characters. Furthermore, the tuning circuit has a control device, comprising a number of push-buttons or keys for transmitting the coded input data to the processing unit, and the circuit device has a device for changing the code, used for coding data, obtained from a number of the aforementioned buttons or keys, in order to obtain a greater number of functions than the number of aforementioned buttons or keys. <IMAGE>

Description

Tuning chain.

The invention relates to a circuit device for tuning a television signal from a number of radioelectric signals, which can be received on a television receiver, connected to a display device, provided with a processing unit, and means for supplying coded input data to the processing unit.

The tuning system commonly used in television receivers for tuning to the desired channels is the so-called frequency "synthesizer" system. With this system, a number of advantages can be achieved by using integrated circuits over the other known systems such as the conventional mechanical memory systems with potentiometer, which were common until not so long ago, and also compared to the more recent so-called voltage synthesizer. systems. The frequency build-up "synthesizer" system is fully electronic, allowing each channel to be queried directly by the user, who indicates the channel number on a keyboard or other operating means. The system usually consists of a quartz-controlled reference oscillator, a phase lock loop, a programmable divider, and a computer, which feeds the number to the programmable divider in response to the channel number set by the user.

The phase lock loop for each channel number set by the user maintains the frequency of the receiver's local oscillator so stably and precisely that the receiver is perfectly matched to the corresponding channel signal. For more detailed information on frequency building tuning systems, see the article "A frequency synthesizer for television receivers" by E.G. Breeze, published in November 1974 in "Transactions BTR magazine", and after L. Penner's article "Digital television tuner uses MOS LSI and non volatile memory", published April 1, 1976 in "Electronics".

The frequency build system lends itself well to a number of different television channel tuning modes: - direct dialing by specifying the required channel number (according to the European standard, the VHF band channels are numbered from 2 to 12 and the UHF band channels from 21 to 69, while according to the US standard the VHF channels from 2 to 13 and the UHF channels from 14 to 83); - memory selection: each of a certain group of keys corresponds to the given channel, which has been selected and previously stored in memory; - automatic scanning of all channels of a given standard or all channels, stored in the memory, or continuous scanning of all available frequency bands.

In the former case, a direct choice can be made of each of the channels of the respective standard (in Europe 60 and in America 82).

In the second case, one of a limited number of preferred channels can be detected more quickly.

In the third case, a quick simple way is provided for figuring out which standard channels can be received, which channels are stored in memory, while further checking whether other broadcasting stations are present at non-standard frequencies such as private broadcasting stations in Italy (of which there are currently more than 100 are employed).

Frequency building systems operating according to the above three options are known from German patent applications 26.45.833 and 26.52.185 and in particular from Italian patent application 69.950-A / 77, filed December 30, 1977 by the applicant.

All of these modes of operation, which are particularly useful in areas where a number of broadcasting stations can be received, require a very complicated control device, which is difficult to operate for many users. This is especially true when, in addition to the necessary controls for setting the transmitter selection and the standard receiver (volume, brightness, color, etc.), provision is also made for additional associated functions such as a digital clock, which require additional adjustment controls. Furthermore, in the event of power interruptions, it should be possible to retain channel information stored in memory. This can be done in the known manner by using a permanent external memory (battery-powered low-power CMOS memory or permanent MNOS memory). Nevertheless, it has been found that some of the information in the memory can be lost during the transition state between power failure and power back.

The object of the invention is to provide a chain construction for a television receiver, with which the above-mentioned many functions can be performed in a simple and inexpensive manner with as few operating problems as possible for the user. More particularly, the invention provides means to increase the number of possible functions.

To this end, according to the invention, a chain device as described in the preamble is characterized in that the chain device has a character generator member, controlled by the processing unit and connected to the display device for generating and displaying ct-numeric characters, that the tuning circuit further has a control element, consisting of a plurality of pushbuttons or keys, for transmitting the encoded input data to the processing unit, and that chain device has a means for changing the code used to encode data obtained from a number of said pushbuttons or keys, in order to obtain a higher number of functions than the number of said push buttons or buttons. The embodiment can herein be such that by means of said code changing member numbers or letters are respectively associated with a given number of other push buttons or keys.

An embodiment is particularly advantageous in which the code-changing member is a special push button or button, which is connected to an electrical or mechanical memory member for bistable operation. This allows, depending on the state of the bistable push button or key, the processing unit to provide the character generator with signals for detecting the state, in order to inform the user that the code used to encode the input data , is changed.

The invention will be explained in more detail below with reference to the drawing, which shows by way of example a favorable embodiment of the chain construction according to the invention. Herein shows:

Fig. 1 is a block diagram of the relevant part of a television receiver according to the invention, and

Fig. 2 is a logic diagram of the operating mode and relative designation selection of the processing unit 11 in FIG. 1.

As shown in Fig. 1, a receiving antenna 1 is connected to a capacitance diode tuner 2, at the output of which a converted intermediate frequency signal is output.

The tuner is of the known type and consists essentially of a selective amplifier stage, a mixing circuit, and a local oscillator circuit.

One output of the local oscillator circuit is connected to a first frequency divider circuit 3, in which a division by a constant number value N1 is performed and the output of which is connected to the signal input of a second divider 4, in which a division is performed by a variable number value N with 12-bit programming, which means that this divisor can divide by any number from 1 to 212.

The output of the divider 4 is connected to a first input of a phase frequency comparator circuit 5, the second input of which receives a differential signal from a quartz generator 6 via a third frequency divider circuit 7. The output of the comparator circuit 5 is connected to the capacitance diode voltage control input of a tuner. amplifier and filter chain 8.

There is also an operating unit 10, which consists of a keyboard, which, in addition to the operating keys not shown in detail, such as for the on / off functions, volume, brightness, contrast and color adjustment, also contains ten number keys, marked with 0 to 9 ( or letter keys, marked with A, B, C, D, E, F, G, Η, I, L), as well as seven auxiliary keys, marked with +, T, C, OR, M, CT (or +, Rl , R2, R3, R4, CT).

This operating unit 10 is connected to a first group of eight input-output terminals of the processing circuit 11 and to the address inputs of the memory chain 12. The processing circuit further comprises a second group of eight input-output terminals, which are connected to the information input output contacts of the memory circuit 12 and the inputs of the character generator circuit 16. This in turn is connected to the display device 9 (which comprises the display tube on the receiver), while a third group of sixteen connection contacts is connected to: - twelve programming inputs of a 12-bit divider 4; - two band switching inputs (U and BUI) of the tuner 2; - a control input of the character generator chain 16; - a first entry of the combining chain 14.

The memory circuit 12 further includes control input terminals connected to the output of the combining circuit 14, which receives a signal from the circuit 11 at a second input and a signal from an on-detector circuit 15 at a third input. The circuit 15 receives a signal from the power supply to which the television receiver is connected, and its output is connected to a reset input of the circuit 11.

The memory 12 and the low current-consuming CMOS combining circuit 14 are connected to a local battery power source 13.

The operation of the above-described chain construction will be explained in more detail below.

The circuits 3, 4, 5 and 8, together with the capacitance diode-driven local oscillator (VCO) in the tuner 2 form a phase lock loop, which is controlled by the reference signal supplied by the quartz generator 6 and divided in a known manner by the divider 7 .

The divider 3 serves to reduce the frequencies involved in more easily processable levels, while the programmable divider 4 can establish the interlock for a number of local oscillator frequencies, i.e.

works as a frequency building chain.

After the division number N has been chosen for the divider circuit 4, the phase frequency comparator 5, the tuning circuit 2 is supplied via the amplifier 8 with a voltage to satisfy the state equations:

f2 = P.N. (2) where f2 is the oscillation frequency of the local oscillator chain in the tuner 2, f6 is the oscillation frequency of the reference oscillator circuit 6, N2> Νχ and N sub-ratios of dividers 3, 6 and 4 and P = f6, respectively - with which the system frequency variation i.e. the extent to which the local oscillation frequency varies with respect to variations of the numerical value N.

The receiver must be capable of being tuned to broadcast stations of a given transmission standard, for example CCIR / BG with a channel format as agreed at the European Radio Broadcasting Conference in Stockholm in 1961, i.e. broadcast stations at one-step intervals between adjacent channels of 7 MHz on the (VHF) bands I and III and channels of 8 MHz on the (UHF) bands IV and V at a video signal bandwidth of 5 MHz. These broadcasting stations fall within television channels 2 and 69 (video carrier frequencies of 48.25 and 855.25 MHz, respectively) at an intermediate frequency of 38.9 MHz. This means that the local oscillator of the tuner must be able to control frequency in the range of 87.15 to 894.15 MHz. When a frequency variation degree P = 0.25 MHz is selected, substitution of this value in the above equation (2) will yield the following values in the above channels:

By varying the numerical value N between this maximum and minimum, you can tune in to any television channel on the VHF and UHF bands with a maximum error of 125 KHz.

This frequency range cannot be used in its entirety, so that the tuner is provided with two band switch inputs U (UHF / VHF) and B (BIII / BI) to ensure that only active bands are covered. Divider 3 is of the very fast emitter-coupled logic (ECL) type, which is divided by 64 (SP 8750). The divider 4 is of the programmable transistor transistor logic (TTL) type, which can operate up to frequencies of about 15 MHz (3 x SN74LS191). Chains 5, 6 and 7 consist of an integrated circuit SP8760 with a quartz crystal frequency of 250 KHz and a dividing ratio N2 = 64, so that comparator 5 operates at a frequency of 3906.25 Hz, which corresponds to a quarter of the line frequency . The amplifier and filter circuit 8 serves to adjust the output level of comparator 5 (maximum 5 V) according to the modes of tuner 2 (maximum 30 V) and ensures the best possible filtering and closing speed.

The circuit 11, which consists of a microprocessor unit, serves, inter alia, to provide numerical values N and band switching signals for tuning to certain television broadcast stations based on information relating to the signals to be tuned as determined by the user from the operating keyboard 10. The circuit 11 can further supply or receive signals from memory 12 and output signals to the character generator 16.

The numerical value N is calculated with the relation: N = (K.F + C). 4 + S (3)

The operations shown are performed by a series of basic operations by the calculation logic unit (ALU) on the basis of commands contained in the permanent program memory, which is part of the operation chain 11, in this case using an F8- microprocessor. The constant correction C and the factor F depend on the chosen band. K is the channel number according to the said standard and the variable S can be changed by making fine tuning corrections.

If the channel number K is changed, only the frequencies corresponding to the standard channels are given a frequency change rate equal to F (8 MHz for the UHF band and 7 MHz for the VHF band), while a variation of one unit of S causes a frequency shift of 0.25 MHz.

With appropriate operation from the keyboard, various modes of tuning to a given broadcasting station are possible, making partial use of known methods.

Each time one of the keys is pressed, the processing unit 11 issues an ISO-encoded 48-character string to the character generator 16, which is usually displayed on the television screen as a three-line string of 16 characters each.

This series always contains a time indication (hours, minutes, seconds). The remainder of this sequence consists partly of fixed data from the permanent program memory (for example, "channel" and "key" shown in Fig. 1) and partly variable data depending on the operations accomplished by the user and the resulting state , which is stored in a memory buffer in the unit 11 (for example, the letter T in the mode of operation indicated in the upper right-hand corner of FIG. 1, the numbers 21-01, also shown in FIG. 1, following the "channel" - indication, which shows the channel number and tuning correction).

The time display is automatically corrected every second, even if no key has been pressed in the meantime.

When one of the keys T, c, OR or M is pressed, the corresponding mode of operation is set and stored in the memory buffer of the processing unit 11. At the same time, one or more question marks are entered into the buffer at appropriate points to guide the user in the next operation. The contents of the buffer are then transferred to the character generator and displayed on the television screen.

Some examples are given below for clarification.

When the T key is pressed, the picture shows: 00: MM: SS T KEY?

In this way, the user is notified that he has selected the T (memory selection) mode of operation and that a number key is expected to be pressed (this is an emitter memory number key). In the example above, N.B .: 00: MM: SS represents the time indication (hours, minutes, seconds).

When the C key is pressed, the picture shows: 00: MM: SS C CHANNEL ??

In this way, the user is notified that he has selected the C mode (direct selection) and two keyboards are expected to be pressed (channel number required).

If the number indicated on these two keys corresponds to a channel in the standard, this number will be displayed instead of the two question marks next to the "CHANNEL" indication. Conversely, if the channel number does not correspond to one in the standard, the figure will show: 00: MM: SS C CHANNEL ?? 88

In this way, the user is informed that the operation setting (channel 88 not covered by the C.C.I.R.standard) has not been made and further instructions are awaited.

When the OR key is pressed, the figure shows:

??: ??: ?? T CHANNEL 21 + 01 KEY 0 OR

From this, the user can conclude that the television receiver is still set to the operating mode T, i.e., tuned to channel 21 with a tuning correction corresponding to one scale shift over 250 KHz, stored in memory with the key 0, and six number keys are expected to be pressed consecutively, corresponding to hours, minutes and seconds, to which the clock must be reset.

When the said six keys are pressed, the corresponding number will be displayed in place of the OR designation and pairs of numbers will replace the symbol ??, which corresponds to hours, minutes and seconds, provided that the numbers are acceptable.

In essence, the device will check the group of numbers and if the hour number is above 23 or the number corresponding to tens of minutes or seconds is above 5, the two numbers (hours, minutes or seconds) are rejected and the two question marks remain displayed to notify the user that the device is waiting for another pair of acceptable numbers to be set. After the operation has taken place, the clock will start counting from the time set by the user.

The arrangement is such that, following a power supply interruption, a series of zeros is displayed for the hours, minutes and seconds and the clock remains in this state to notify the user that the power supply has been temporarily interrupted.

When the M key is pressed, the picture will show: 00: MM: SS T CHANNEL 21 + 01 KEY #? Μ

This informs the user that the television is still in operating mode T, that is, tuned to channel 21 with +01 tuning, and that it is waiting for a number key to be pressed to select the channel being tuned, to keep in memory. For example, if the 0 key is pressed, the image shown in Figure 1 will appear and the channel will be coupled with the 0 key for memory selection.

When the + key is pressed the display will show: 00: MM: SS T CHANNEL 21 + 02 KEY 0

This informs the user that the television is still set to the T mode and that additional tuning corrections are made, i.e. in the direction of the sound beam of the received video signal.

Obviously, due to the presence of the programmable divider chain cell, the chain 11, a suitably modified number N is issued and this tuning state is automatically associated with the key 0 in memory. Similar operation occurs when the "-" button is pressed except for the directions of the tuning setting (toward the video). Once a nominal tuning is reached, the "+" sign and the next number can be cleared, while for more imperfect tuning states, the "" sign appears, followed by the number of moves performed. The system is designed to limit maximum variations to the range from -16 to +15.Of course, the tuning correction can be performed in the same way, even when the unit is in the direct selection operating mode C. In this case, the operation is not accompanied by an automatic memory storage. channel and the obtained tuning state, which are to be stored in memory, press the M button followed by a number button.

When the key (keyboard switch) CT is pressed, the following image appears: 00: MM: SS * T *

CHANNEL 21 + 01 KEY O

The symbol indicates the working position display. This notifies the user that the device is set to perform a further set of functions corresponding to the second indication on each key. In this operation, the processing unit 11 will output to the drawing generator 16 a switching signal for switching the color of the inscription on the screen or the background color in order to make it more clear to the user that the operations available from this point on correspond to the second key instructions (this of course applies to color television receivers).

if one of the keys A to L is pressed, the picture will show: ΟΟίΜΜ: SS * C *

CHANNEL A

This informs the user that the television is set to the operating mode C, but in this case the channels can be selected directly according to the Italian standard by pressing a single key indicating the received channel.

When one of the keys R1, R2, R3 or R4 is pressed, the picture shows for example: 00: MM: SS * 1 * CHANNEL 21 + 01

KEY O RA

This informs the user that the device is performing an automatic scanning operation, for example of type 1, or that all channels in the memory are being scanned.

Scanning will continue automatically every two seconds with instructions from the keyboard and associated channel. At the same time, the processing circuit 11 supplies the relative N numbers for receiving the channel. Scanning is stopped when another key is pressed. If the "+" or "key is pressed, the unit remains set to perform forward or reverse operation steps manually (each time the" + "key is pressed, the key number is increased and each time the key is pressed, the channel number is reduced.) If the CT key is pressed, the unit switches back to the first keyboard and waits for further commands, in particular for tuning correction operations to memory storage. Likewise, if the R2 key is pressed after dialing of the second keyboard using the CT key, a type 2 scan operation is pressed to scan all standard channels (one switch per second) This can be terminated in the same way as the type 1 scan operation.

When the R3 key is pressed, it initiates the continuous scanning of the frequency band in 1 MHz steps, i.e. four fine tuning switches per second, to detect the operation of a transmitter over non-standard frequencies. The same type of scanning operation, although at a reduced speed (one switch every 2 seconds) is initiated by pressing the R4 key.

The indication "KEY" is not displayed during the scanning operations of types 2, 3 and 4.

The display or omission of the fixed channel and key indicia depends on whether the indication or blank sectors of the permanent memory are used. The circuit 11 further includes a timer 15 seconds after the last key is operated, outputting a switching signal (bit 6 port 1) to the character generator 16, which reduces the image by one line and also reduces the height of these characters (7 instead of 14 television lines) in order to reduce picture interference. This switching signal is of course not supplied during the automatic scanning or clock setting.

In order to prevent information stored in memory from being lost during a power interruption, a battery-powered external memory access device is provided. Whenever a memory operation is performed, the processing unit 11 will update the information in the immediately accessible memory. When the power supply is restored, the processing unit 11 will again request the information stored in the directly accessible memory.

The "ON RESET" circuit 15 and combining circuit 14 secure the information stored in the freely accessible memory 12 during transition states between power failure and recovery.

The operating program of the processing unit 11 is represented in the logic diagrams according to Figs. 2, 3 and 4, of which Fig. 2 shows the operating mode and relative indication selection, Fig. 3 the updating of the information in the external freely accessible memory 12, and Fig. 2. 4 represents the requesting of the information from the external, freely accessible memory 12, which follows the recovery of the power supply.

In Fig. 2, a timing circuit 20 is set by a timer 20, the output of which is usually fed to block 23, from which an RTI signal is supplied to block 21, in which the controls set on the keypad are read. A signal is supplied from block 21 via a switch 22 to block 23, which confirms the presence of a new command. The "no" output provides the RTI signal, which energizes the read block 21, while the "yes" output energizes the block 24, which determines whether the key pressed was an operating mode key. The "no" output of the block 24 energizes the block 25, which examines the selected mode of operation and in turn energizes the block 26, which, depending on the selected mode of operation, combines and feeds the designation sequence to be displayed. Block 26 then energizes a block 27, which examines the pressed number keys and activates block 28, which determines whether the corresponding sequence is possible.

The "no" output from block 28 (operation not possible, e.g. the number does not correspond to a standard number channel) energizes a subsequent block 34, which inputs question marks into the buffer at appropriate points to inform the user that the operation is not possible and supplies these question marks to the character generator 16 (fig. 1). Block 34 then supplies an RTI signal to block 21, which reads the keyboard again while waiting for further commands.

The "yes" output of the block 28 energizes the block 29, which outputs the channel number to the buffer, usually numbers of the received sequence, supplies the numbers to the character generator, and finally energizes the block 30, reaching the number N according to apply the above equation (3) and this number to a programmable divider 4 (Fig. 1) to obtain the desired tuning Finally, the RTI signal is output from the block 21 to the block 21.

With the "yes" output of block 24, the block 36 is energized, with which the prompts and question marks are input into the buffer and transferred to the character generator (as already described). The block 36 then supplies RTI signal to the block 21. After a set period of time (approx. 4 milliseconds) depending on the circuit 20, the switch 22 will be set with its output to the counter chain 31, which after a set number pulses (about 250) per second outputs a signal to block 32, which updates the clock numbers in the buffer and energizes block 33, which outputs the information stored in the buffer to the character generator and then outputs an RTI signal to block 21.

Although the above exemplary embodiments used a particular type of 8-bit microprocessor system with a separate central processing unit and permanent memory, it is also possible and sometimes advantageous to use other types of microprocessors and high numbers of internally accessible memory registers (for example 128) or to use a so-called monochip, which contains, in addition to permanent memory, an internally directly accessible memory and a timing chain, or a 16-bit microprocessor. It may also be useful to provide the receiver with a remote control. In this case, a keyboard, as described, is combined on a portable transmitter part or remote control system. In order to avoid duplication of the operating keyboard, a number of electrical contacts can also be arranged in the receiver housing for a connection to the transmitter part in order to operate the local control.

It will be clear that the invention is in no way limited to the above-described embodiments, but that many modified embodiments can be developed without departing from the scope of the invention.

Claims (4)

Chain arrangement for tuning a television signal from a number of radioelectric signals which can be received on a television receiver, connected to a display device, provided with a processing unit, and means for supplying coded input data to the processing unit, characterized in that the chain device has a character generator, controlled by the processing unit and connected to the display device for generating and displaying α-numeric characters, the tuning chain further having a controller, consisting of a number of push buttons or keys, for transmitting the coded input data to the processing unit, and that circuit device has a means for changing the code used to encode data obtained from a number of said push buttons or keys, in order to obtain a higher number of functions than the number of said push buttons or - tests. 2. Chain device according to claim 1, characterized in that by means of said code-changing member numbers or letters are respectively associated with a given number of other push buttons or keys. Chain device according to claim 1, characterized in that the code changing member is a special push button or button, which is connected to an electrical or mechanical memory device for bistable operation. Chain device according to claim 3, characterized in that, depending on the state of the bistable push button or key, the processing unit supplies the character generator with signals for detecting the state, in order to inform the user that the code used for the coding of the input data has changed.