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Update ALU comments

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This commit is contained in:
Sean O'Connor
2025-09-03 10:18:19 -04:00
parent c2cea97f87
commit 22e0b42305
1 changed files with 4 additions and 0 deletions
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02/ALU.hdl
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@@ -66,9 +66,13 @@ CHIP ALU {
Mux16(a=fout, b=notfout, sel=no, out=out, out[0..7]=outLow, out[8..15]=outHigh, out[15]=sign); 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)
// check if any bits in low 8 are set
Or8Way(in=outLow, out=tmp1); Or8Way(in=outLow, out=tmp1);
// check if any bits in high 8 are set
Or8Way(in=outHigh, out=tmp2); Or8Way(in=outHigh, out=tmp2);
// combine both halves (true if any bit is set)
Or(a=tmp1, b=tmp2, out=notzr); Or(a=tmp1, b=tmp2, out=notzr);
// zr = true if no bits are set (output is zero)
Not(in=notzr, out=zr); Not(in=notzr, out=zr);
// compute ng (negative flag) // compute ng (negative flag)