EFM encoder and DSV calculator
First Claim
1. An EFM (Eight to Fourteen Modulation) encoder comprising:
- a merging-bit selector for selecting merging-bit data which connects to each other any adjacent two of a plurality of frame signals sequentially inputted,said merging-bit selector having a DSV calculator for calculating DSV (Digital Sum Variation) as an index for selecting the optimum merging-bit data for each frame signal and for each merging-bit data;
said merging-bit selector further comprising;
a merging-bit generator for generating, for each of the inputted frame signals, the merging-bit data which connects said frame signal as a first frame signal to a second frame signal immediately preceding the first frame signal;
said DSV calculator having a function of receiving frame-signal DSV data representing a value of DSV of the first frame signal, a frame-signal polarity signal indicating whether or not polarity inversion has occurred in a leading bit or final bit of the first frame signal, cumulative DSV data representing a value of DSV up to the second frame signal, and a cumulative polarity signal indicating a polarity in a final bit of the second frame signal, calculating DSV based on said frame-signal DSV data, on said frame-signal polarity signal, on said cumulative DSV data, on said cumulative polarity signal, and on the merging-bit data generated by said merging-bit generator, generating new cumulative DSV data representing a value of DSV up to the first frame signal and a new cumulative polarity signal indicating a polarity in the final bit of the first frame signal, and outputting them;
said DSV calculator further comprising;
a merging-bit DSV calculator which receives said merging-bit data and said cumulative polarity signal and outputs merging-bit DSV data representing a value of DSV of said merging-bit data and a provisional cumulative polarity signal indicating a polarity in a final bit of said merging-bit data when said merging-bit data is connected to the second frame signal;
a frame-signal DSV/polarity evaluator which receives said frame-signal DSV data, said frame-signal polarity signal, and said provisional cumulative polarity signal outputted from said merging-bit DSV calculator, substitutes frame-signal DSV data after polarity evaluation for said frame-signal DSV data in consideration of a polarity of said provisional cumulative polarity signal, and outputs the frame-signal DSV data after evaluation, while outputting, as said new cumulative polarity signal, a signal indicating a polarity in the final bit of the first frame signal when said frame signal is connected to the second frame signal via said merging-bit data;
adding means for adding up said cumulative DSV data, said merging-bit DSV data outputted from said merging-bit DSV calculator, and said frame-signal DSV data after polarity evaluation outputted from said frame-signal DSV/polarity evaluator so as to output a result of addition as said new cumulative DSV data; and
an overflow/underflow processor which judges whether or not overflow or underflow has occurred in the new cumulative DSV data outputted from said adding means and performs exception handling with respect to said new cumulative DSV data when overflow or underflow has occurred therein.
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Accused Products
Abstract
There is provided an EFM encoder comprising a DSV calculator which is smaller in circuit scale than a conventional DSV calculator. The above DSV calculator has a merging-bit DSV calculator, a frame-signal DSV/polarity evaluator, adding means, and an overflow/underflow processor. The merging-bit DSV calculator calculates merging-bit DSV data based on merging bits and on a cumulative polarity signal. The frame-signal DSV/polarity evaluator outputs frame-signal DSV data in consideration of the polarity in the final bit of the merging bits. The adding means adds up the cumulative DSV data, the merging-bit DSV data, and the frame-signal DSV data so as to calculate DSV. The overflow/underflow processor performs, when overflow or underflow has occurred in the result of calculation from the adding means, exception handling with respect to the calculation result and outputs the calculation result that has undergone the exception handling as new cumulative DSV data. Even when overflow or underflow has occurred in the obtained cumulative DSV data, the accuracy of DSV calculation performed by the DSV calculator is not reduced.
23 Citations
13 Claims
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1. An EFM (Eight to Fourteen Modulation) encoder comprising:
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a merging-bit selector for selecting merging-bit data which connects to each other any adjacent two of a plurality of frame signals sequentially inputted, said merging-bit selector having a DSV calculator for calculating DSV (Digital Sum Variation) as an index for selecting the optimum merging-bit data for each frame signal and for each merging-bit data; said merging-bit selector further comprising; a merging-bit generator for generating, for each of the inputted frame signals, the merging-bit data which connects said frame signal as a first frame signal to a second frame signal immediately preceding the first frame signal; said DSV calculator having a function of receiving frame-signal DSV data representing a value of DSV of the first frame signal, a frame-signal polarity signal indicating whether or not polarity inversion has occurred in a leading bit or final bit of the first frame signal, cumulative DSV data representing a value of DSV up to the second frame signal, and a cumulative polarity signal indicating a polarity in a final bit of the second frame signal, calculating DSV based on said frame-signal DSV data, on said frame-signal polarity signal, on said cumulative DSV data, on said cumulative polarity signal, and on the merging-bit data generated by said merging-bit generator, generating new cumulative DSV data representing a value of DSV up to the first frame signal and a new cumulative polarity signal indicating a polarity in the final bit of the first frame signal, and outputting them; said DSV calculator further comprising; a merging-bit DSV calculator which receives said merging-bit data and said cumulative polarity signal and outputs merging-bit DSV data representing a value of DSV of said merging-bit data and a provisional cumulative polarity signal indicating a polarity in a final bit of said merging-bit data when said merging-bit data is connected to the second frame signal; a frame-signal DSV/polarity evaluator which receives said frame-signal DSV data, said frame-signal polarity signal, and said provisional cumulative polarity signal outputted from said merging-bit DSV calculator, substitutes frame-signal DSV data after polarity evaluation for said frame-signal DSV data in consideration of a polarity of said provisional cumulative polarity signal, and outputs the frame-signal DSV data after evaluation, while outputting, as said new cumulative polarity signal, a signal indicating a polarity in the final bit of the first frame signal when said frame signal is connected to the second frame signal via said merging-bit data; adding means for adding up said cumulative DSV data, said merging-bit DSV data outputted from said merging-bit DSV calculator, and said frame-signal DSV data after polarity evaluation outputted from said frame-signal DSV/polarity evaluator so as to output a result of addition as said new cumulative DSV data; and an overflow/underflow processor which judges whether or not overflow or underflow has occurred in the new cumulative DSV data outputted from said adding means and performs exception handling with respect to said new cumulative DSV data when overflow or underflow has occurred therein. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A DSV calculator for calculating, upon receiving each frame signal, DSV as an index for selecting merging-bit data which connects modulated frame signals to each other, said DSV calculator comprising:
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adding means for adding up cumulative DSV data representing a value of DSV up to the frame signal immediately preceding said frame signal, frame-signal DSV data representing a value of DSV of said frame signal, and merging-bit DSV data representing a value of DSV of the merging-bit data which connects said frame signal to the immediately preceding frame signal so as to output a result of addition; and an overflow/underflow processor for judging whether or not overflow or underflow has occurred in the addition result outputted from said adding means, performing exception handling with respect to said addition result when overflow or underflow has occurred therein, and outputting said addition result that has undergone the exception handling as new cumulative DSV data, wherein said overflow/underflow processor has a function of holding, when overflow has occurred in the addition result outputted from said adding means, a difference between said addition result and a maximum value of said cumulative DSV data and adding, when overflow has not occurred in said addition result outputted from said adding means, the held difference to said addition result, while holding, when underflow has occurred in the addition result outputted from said adding means, a difference between said addition result and a minimum value of said cumulative DSV data and adding, when underflow has not occurred in the addition result outputted from said adding means, the held difference to said addition result. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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Specification