| 摘要 |
PURPOSE: A device for controlling an address in accordance with data compression and expansion is provided to generate a corresponding address according to a ratio conversion while compressing or expanding data, so as to simplify hardware and remove data errors caused by a conversion of input/output ratios. CONSTITUTION: A ratio conversion controller comprises as follows. A subtracter(11) subtracts an input ratio and an output ratio. The first comparator(12) selectively inputs and outputs input/output ratios according to a maximum valid bit of binary data. The first latch(14) latches the input/output ratios one to one, and outputs the latched ratios. The second comparator(13) selectively outputs one of the input/output ratios of the latch(14) and reversed input/output ratios, according to the maximum valid bit. An address generator comprises as follows. The first adder(20) adds the input/output ratios to a previous address value. The second adder(21) adds the added value to the input/output ratios of the ratio conversion controller, and outputs a maximum valid bit value. The third comparator(18) inputs the added value of the first adder(20) and the second adder(21), and selectively outputs the added value according to the maximum valid bit value. The second latch(15) latches an output value of the third comparator(18) to output an address value, and feeds a previous address value back to the first adder(20).
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