This project contains all the files for a 8-bit arithmetic-logic unit made in the Digital simulator. It is made of only basic gates (this mainly means that I did not use any more complicated things like sumators or multipliers) -- almost 3500 of them.
The unit supports the following operations (the arithmetic ones are all signed):
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Addition
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Subtraction
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Multiplication
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Division + modulo
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Shift and rotate in both directions
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AND, OR, XOR, NOT
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PASS (can be used for flags)
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Twos compliment
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INC and DEC
The ALU has three input registers and three output registers. The two input 8-bit registers are used for the two operands and the other 4-bit register is used for selecting the OPT code
There are two output 8-bit registers, usually only one is used but for multiplication they connect into one 16-bit register. For DIV/MOD one of them is for division result and one for modulo result. There is also a 6-bit flag register with the following flags about the result:
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Overflow (OF)
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Zero (Z)
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Less than zero (LZ)
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Greater than zero (GZ)
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Parity (PAR)
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Error (ERR) -- only used for division by 0
You need to have Digital installed. Then you can either open the demo.dig file for easy usage of the ALU or any of the other files to see some smaller components used in the ALU. The alu.dig file contains the ALU itself.