Data processor performing a decimal multiply operation using a read only memory
AssigneeHoneywell Information Systems Inc.
InventorsVirendra S. Negi, Steven A. Tague
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Abstract
A data processor performs a decimal multiply operation using apparatus including a register for storing multiplier decimal digits, a register for storing a multiplicand operand of decimal digits, a register for storing partial products and arithmetic logic units, and a read only memory for storing the units and tens product digits. The multiplier digit and a selected multiplicand digit are applied to the address terminals of the read only memory. On successive cycles, the units product digit and the tens product digit are added respectively to selected partial product digits and the sum replaces the selected partial product digits.
Claims16
A decimal multiplying system for multiplying a multiplicand by successive decimal digits of a multiplier comprising:
- first register means for storing decimal digits of said multiplicand;
- second register means for storing said multiplier decimal digits;
- multiply register means coupled to said second register means for storing each of said successive multiplier decimal digits;
- said second register means coupled to said first register means for storing said multiplicand decimal digits after said each of said successive multiplier decimal digits are stored in said multiply register means;
- read only memory means coupled to said multiply register means and said second register means and responsive to a selected multiplier decimal digit and each of said multiplicand decimal digits for generating a units product decimal digit on a first cycle of operation and a tens product decimal digit on a second cycle of operation for said each multiplicand decimal digit;
- third register means for storing partial product decimal digits;
- adder means coupled to said read only memory means and said third register means and responsive to each of said units product decimal digit and a corresponding first partial product decimal digit during each of said first cycles of operation for generating a first sum decimal digit for replacing said first corresponding partial product digit in said third register means,
- and responsive to each of said tens unit product decimal digit and a second corresponding partial product decimal digit during each of said second cycles of operation for generating a second sum decimal digit for replacing said second corresponding partial product digit in said third register means.
Multiplier apparatus for a data processing system which operates by applying successive multiplicand decimal digits for each decimal digit of a multiplier to a read only memory storing units product decimal digits and tens product decimal digits comprising:
- (A) first storing means for storing said multiplier and said multiplicand decimal digits;
- (B) multiply means coupled to said first storing means for receiving said multiplier and said multiplicand decimal digits including,
- multiply register means for storing each of said multiplier decimal digits,
- said read only memory coupled to said multiply register means and responsive to one of said each of said multiplier decimal digits and each of said multiplicand decimal digits for generating a units product decimal digit and a tens product decimal digit for said each of said multiplicand decimal digits, said read only memory further generating a plurality of said units product decimal digits and a plurality of said tens product decimal digits for said each of said multiplicand decimal digits when said each of said multiplier decimal digits stored in said multiply register means is applied to said read only memory;
- (C) second storing means for storing partial product decimal digits;
- (D) adder means coupled to said second storing means and said multiply means for adding said plurality of units product decimal digits and said plurality of tens product decimal digits to their respective partial product decimal digits for generating final product decimal digits for storage in said second storing means.
Dependencies are inferred from the claim text.