Abstract:
Apparatus for automatically restoring information concerning a plurality of broadcast station frequencies in a microprocessor type tuning system when such information is inadvertently lost from a volatile memory.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to that described and claimed in application Ser. No. 932,141 filed Aug. 9, 1978 and assigned to the same assignee as this application. 
     The forementioned application describes a microprocessor control system for affecting channel selection and function level adjustments. The system uses an electrically alterable ROM to store television broadcast station or channel information which is retrieved by the microprocessor and converted by a digital-to-analog converter into voltages for use by a varactor tuner to tune in channels on a television receiver. Should the electrically alterable ROM lose some or all of the channel information stored in it, a repairman would have to reinsert that information manually in order for the receiver to be able to be tuned to the channels corresponding to the lost information. Alternatively the microprocessor could have stored in its internal ROMs all of the channel information which was also stored in the electrically alterable ROM. Neither of these alternatives is acceptable. The former because it would require the repairman to expend an inordinate amount of time in order to insert this information manually into the ROM. The latter because the duplication would use up too much of the capacity of the internal ROMs. 
     SUMMARY OF THE INVENTION 
     In accordance with the invention, a program and selective channel information is stored in the microprocessor by which approximate channel information for the electrically alterable ROM can be reconstructed by the microprocessor and restored to the electrically alterable ROM automatically. This relieves the repairman of the need of having to do all of this manually. It also uses much less capacity of the internal ROMs than would be used if all of the channel information for the electrically alterable ROM was also to be stored in the internal ROMs. 
    
    
     DESCRIPTION OF THE FIGURES 
     FIG. 1 is a schematic drawing of the apparatus by which the invention is practiced. 
     FIG. 2 is a flow diagram of the program for practicing the invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows apparatus which is also shown in FIG. 2 of the forementioned application Ser. No. 932,141. Rather than duplicate the description of that apparatus contained therein that application is incorporated entirely herein by reference. 
     From the flow chart of FIG. 2 and the program which follows as listed, a skilled programmer could duplicate the constructed embodiment of the invention and practice it in accordance with the preferred manner. In the constructed embodiment, there was stored in the internal ROMs of microprocessor 25 binary information identifying the voltage levels required across the varactor tuner in order to tune to each of the VHF channels 2 through 13. The following table shows the voltage levels for each of these channels for the particular varactors employed in the tuner of the constructed embodiment. 
     
         ______________________________________              Tuning VoltageChannel            Volts______________________________________VHF2                  4.53                  6.84                  9.35                  14.76                  22.07                  11.08                  12.19                  13.110                 14.411                 15.812                 18.013                 22.0UHF10                 1.520                 3.830                 6.240                 9.050                 11.860                 14.270                 17.180                 22.0______________________________________ 
    
     The apparent ambiguities in the voltages for the VHF channels in this table exist because the inductance of the tuner is changed depending upon whether channels 2 through 6 are being tuned or whether channels 7 through 13 are being tuned. The particular tuner used employs less inductance when tuning channels 7 through 13 than when tuning channels 2 through 6. This decreased inductance in the tuned circuits automatically raises their resonant frequencies and lowers the voltage which is needed across the varactors to tune channels 7 through 13. 
     Also stored in digital form in the internal ROMs of microprocessor 25 is information identifying predetermined ones of the UHF channels. The foregoing table shows the voltage levels for tuning each one of the selected UHF channels whose identifying information is stored in the internal ROMs. From these voltage levels it can be seen that the varactor tuner used for the UHF channels is different from that used for the VHF channels. It can also be seen that information identifying a channel 10 in the UHF band was stored. Of course there is no channel 10 in the UHF band. Information which would be equivalent to a channel 10 in the UHF band was stored however, in order to simplify the program by which the information identifying each of the UHF channels is reconstructed. The other selected UHF channels are those which start each of the decades in the UHF spectrum, namely, channels 20, 30, 40, 50, 60, 70 and 80. 
     From the foregoing table it can be seen that the UHF channel at the start of each decade in the spectrum is separated from the UHF channel at the start of the next highest decade by a known voltage. It can also be seen that each of these voltage separations is not the same. By dividing each of these voltage separations by ten an increment is obtained which approximately represents the difference between each adjacent UHF channel in each decade. Information in digital form representing each of these increments is also stored in the internal ROM of the microprocessor. 
     In practicing the invention a particular entry would be made in keyboard 20. Thereupon microprocessor 25 would start the program as listed. During the course of that program microprocessor 25 would retrieve from the storage means comprising its internal ROMs the digital information identifying each of the VHF channels and would store that information in particular locations in the electrically alterable ROM 21. After completing that retrieval and storage operation, microprocessor 25 would then retrieve the digital information corresponding to UHF channel 10 from the appropriate location in its internal ROM. This information would be stored in a temporary register. The 10s decade increment would then be retrieved from the internal ROM. After multiplying this increment by 4 the resulting binary number would be added to the digital information identifying UHF channel 10 and that result would at least, approximately identify UHF channel 14. This identifying information would then be stored in an appropriate location in electrically alterable ROM 21. The digital information, at least approximately identifying the channels in each of the decades is similarly reconstructed from the identifying information of the channel at the start of the associated decade and the associated increment until all 70 UHF channels are stored in electrically alterable ROM 21. 
     Although the stored information for the most part will only approximate that identifying the UHF channels it is accurate enough to enable each of the channels to be tuned in closely enough to permit the receiver&#39;s automatic fine tuning control to tune in each channel accurately once selected. Microprocessor 25 then updates the information for that station in electrically alterable ROM 21. 
     Changes in the above embodiment are possible without departing from the scope of the invention. Consequently it is intended that all matter contained in the above or shown in the accompanying drawings be interpreted as illustrative and not in any sense limiting. ##SPC1## ##SPC2##