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project02: Comments/cleanup

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This commit is contained in:
Sean O'Connor
2025-09-03 22:55:08 -04:00
parent 934f1ad2f5
commit e1c0b091a8
2 changed files with 9 additions and 6 deletions
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12
02/ALU.hdl
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@@ -65,16 +65,16 @@ CHIP ALU {
Not16(in=fout, out=notfout);
Mux16(a=fout, b=notfout, sel=no, out=out, out[0..7]=outLow, out[8..15]=outHigh, out[15]=sign);
// compute zr (zero flag)
// compute zr (zero flag): set if output is all zeros
// check if any bits in low 8 are set
Or8Way(in=outLow, out=tmp1);
Or8Way(in=outLow, out=lowOnes);
// check if any bits in high 8 are set
Or8Way(in=outHigh, out=tmp2);
Or8Way(in=outHigh, out=highOnes);
// combine both halves (true if any bit is set)
Or(a=tmp1, b=tmp2, out=notzr);
// zr = true if no bits are set (output is zero)
Or(a=lowOnes, b=highOnes, out=notzr);
// zr set if no bits are set (output is zero)
Not(in=notzr, out=zr);
// compute ng (negative flag)
// compute ng (negative flag): set if leftmost bit is 1 (two's complement)
And(a=sign, b=true, out=ng);
}