| 摘要 |
PURPOSE:To detect signal quality margin correctly without being affected with a shape of a SQM decision area by squaring equalization correction quantities of registers respectively, comparing them with a prescribed value so as to detect the spread of a '1' output at a ROM. CONSTITUTION:Values of elements 2a-2e of a register storing an equalization correction quantity are formed into values compensating the inter-code interference caused by the distortion of a data line. When the distortion of a line is increase, the content of the register 2 changes, its output is squared by square devices 7a-7e, the square output is compared with a prescribed value at comparators 8a-8e, and when a square output is larger, a level '1' is outputted and becomes an address input to a ROM circuit 9. Then an area where the output of the comparator is at '1' is moved from the elements 2b, 2d to the elements 2a, 2e, then the decrease in the signal quality margin is decided. The output is increased in the ROM 9 corresponding to the spread of '1' in advance and when the output is larger, it is decided that the signal quality margin is less when the output is larger.
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