| 摘要 |
A combined binary and binary coded decimal (BCD) arithmetic logic unit (binary/BCD ALU) having a binary adder adapted to perform decimal operations on BCD data without impacting the performance of binary operations. The combined binary/BCD ALU has a look-ahead carry binary adder for generating the binary sum or logical combination of inputs to the binary adder to an output (Y), the Y output being arranged in groups of four bits. The binary adder additionally provides carry outputs Coi of the binary additions from each of the groups of four bits of the Y output. A decimal correction unit, responsive to the Y and Coi outputs from the binary adder [ALU means], corrects the binary sum from the binary adder when performing BCD arithmetic. A multiplexer selects the Y output from the binary adder to a result output when performing operations on binary data. Alternately, the multiplexer selects the output from the decimal correction unit to the result output performing operations on BCD data.
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