One Bit ALU supporting:
===========================
• AND / NAND (1000000 / 0100011)
• OR / NOR (0100000 / 1000011)
• XOR / XNOR
(0010000 / 0010010 or 0010001)
• A+B / A-B (0001000 / 0000100)
Inputs (counted top to bottom):
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1-7 = OP-Code (see in brackets above
or description below)
8 = A
9 = B
10 = Ci (Carry IN / Sign IN)
Outputs (LEDs on the right side):
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Green LED (upper) = R (Result)
Yellow LED (lower) = Co
(Carry OUT / Sign)
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The 5 logic gates in the upper right corner along with the 7-segment display don't belong to the ALU, they just decode positive and negative carry / sign bits.
The decimal dot shows that the result is a negative number.
OP-Code 0000000 means NOP (No Operation), valid OP-Codes see above, all other bit combinations are not defined.
The OP-Code bits 1-7 mean:
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1 = AND
2 = OR
3 = XOR
4 = ADD
5 = SUBTRACT B from A
6 = Negate A
7 = Negate B
Hence:
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NAND = NotA OR NotB
NOR = NotA AND NotB
XNOR = NotA XOR B --or-- A XOR NotB
