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US 5,327,364 AGranted
Arithmetic logic unit for microprocessor with sign bit extended
AssigneeChips and Technologies, Inc.
InventorsMorris E. Jones, Jr., James A. Picard
Life of this patent
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AssigneeChips and Technologies, Inc.
InventorsMorris E. Jones, Jr., James A. Picard
Estimating the term…
An arithmetic logic unit for a microprocessor is shown and described for use in a 24-bit data path where the ALU includes three separate ALU portions, one for each byte of the data path, and three separate control signals, one for each portion of the ALU. The ALU provides a variety of arithmetic and logic functions for application to 24-bit operands, but also includes a capability of manipulating such operands in accordance with sign extended opcodes without actually physically executing a sign extend operation within the microprocessor. In this manner, the ALU executes the necessary logic functions to provide the same ultimate result as sign bit extension, but does not require a separate sign bit extension step within the microprocessor to convert signed byte operand into a signed word operand.
A circuit for operating upon in one cycle a signed byte operand "A" and a signed byte operand "B" responsive to a control signal "C", to produce a result signal, said control signal "C" indicating a particular arithmetic-logical operation and including sign extension op code indicia, each of said operands "A" and "B" having a low operand byte, a middle operand byte, and a high operand byte, said control signal having a low control byte, a middle control byte and a high control byte, said circuit including:
A circuit for performing arithmetic and logic functions having an "A" operand input, a "B" operand input, a control signal input "C", and a result output, the result output being a function of the values of the "A" operand, the "B" operand and control signal inputs, each of said A operand, "B" operand, control signal "C" and result having a low order byte, a middle order byte and a high order byte, said circuit comprising:
Dependencies are inferred from the claim text.