Apparatus for synchronizing the operation of a microprocessor with a television synchronization signal useful in generating an on-screen character display
First Claim
1. Apparatus comprising:
- computing means operating in response to stored program instructions generated in timed relationship to instruction cycles occurring at a rate synchronously related to a clock signal;
clock signal generating means for generating said clock signal and for controlling the phase and frequency of said clock signal in response to a control signal;
a source of a reference frequency signal having a reference frequency;
said computing means being programmed to generate a comparison signal each time a predetermined number of instruction cycles have occurred; and
comparison means for comparing the phase and frequency of said comparison signal and said reference signal and generating said control signal in response thereto.
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Accused Products
Abstract
A microprocessor embodied in an integrated circuit has a clock signal generator comprising an inverter in the integrated circuit and a frequency determining network external to the integrated circuit connected to the inverter through terminals. The clock signal generator generates a clock signal which determines the frequency of the instruction cycles of the microprocessor. The operation of the microprocessor is synchronized with a television horizontal rate signal by programming it to generate a comparison signal each time a predetermined number of instruction cycles, selected so that the comparison signal has the same nominal frequency as the horizontal rate signal have occurred. The simple wired AND gate serves as coincidence detector for the horizontal rate signal and the comparison signal and generates a pulse error signal representing the phase and frequency deviations between its two input signals. The error signal is filtered and coupled to the inverter to control the phase and frequency of the clock signal. This microprocessor synchronization arrangement is used to form characters on the screen of a picture tube without the need of an additional character generator.
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Citations
23 Claims
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1. Apparatus comprising:
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computing means operating in response to stored program instructions generated in timed relationship to instruction cycles occurring at a rate synchronously related to a clock signal; clock signal generating means for generating said clock signal and for controlling the phase and frequency of said clock signal in response to a control signal; a source of a reference frequency signal having a reference frequency; said computing means being programmed to generate a comparison signal each time a predetermined number of instruction cycles have occurred; and comparison means for comparing the phase and frequency of said comparison signal and said reference signal and generating said control signal in response thereto. - View Dependent Claims (2, 3, 4, 5, 6)
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7. In a television system, apparatus comprising:
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computing means operating in response to program instructions generated in timed relationship to instruction cycles occurring at a rate synchronously related to a clock signal; clock signal generating means for generating said clock signal and for controlling the phase and frequency of said clock signal in response to a control signal; a source of a television horizontal rate signal defining the rate at which horizontal scanning intervals occur; said computing means being programmed to generate a comparison signal each time a first predetermined number of instruction cycles have occurred; comparison means for comparing the phase and frequency of said comparison signal and said horizontal rate signal and generating said control signal in response thereto; and said computing means being programmed to perform a predetermined operation at a second predetermined number of instruction cycles after the generation of said comparison signals in any of said scanning intervals. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. Apparatus comprising:
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a microprocessor embodied in an integrated circuit and operating in response to programmed instructions generated in timed relationship to instruction cycles occurring at a rate synchronously related to a clock signal; clock signal generating means for generating said clock signal and for controlling the phase and frequency of said clock signal in response to a control signal, said clock signal generating means comprising an amplifying device included within said integrated circuit having an input and an output connected to first and second terminals of said integrated circuit, respectively, and a frequency determining network connected in a feedback network between said input and said output of said amplifying device through said terminals; a source of a reference frequency signal having a reference frequency; said microprocessor being programmed to generate a comparison signal at a third terminal of said integrated circuit each time a predetermined number of instruction cycles have occurred; and coincidence detector means coupled to said source and said third terminal for generating a pulse at a circuit point when said reference frequency signal and said comparison signal are coincident; and filter means coupled between said circuit point and said first terminal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21)
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22. In a television system for forming an image on an image display device which is scanned in lines during line scanning intervals, apparatus comprising:
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a microprocessor embodied in an integrated circuit and operating in response to programmed instructions generated in time relationship to instruction cycles which occur in time relationship to a clock signal; clock signal generating means for generating said clock signal and for controlling its phase and frequency in response to a control signal; a source of a television synchronization signal defining the rate at which said line scanning intervals occur; synchronization means responsive to said clock signal and to said television synchronization signal for generating said control signal so as to synchronize said clock signal and thereby said instruction cycles with said television synchronization signal; a source of data signals corresponding to a character; said microprocessor being programmed for generating character pulses at a rate proportional to that of said instruction cycles during ones of said line scanning intervals; coupling means for coupling said character pulses to said image display device, said image display device being responsive to said pulses to display slices of said character. - View Dependent Claims (23)
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Specification