Dedicated top of carry pin is sourced from O[Y_WIDTH].

SymbiFlow / yosys

SymbiFlow WIP changes for Yosys Open SYnthesis Suite

http://www.clifford.at/yosys/

ISC License

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Dedicated top of carry pin is sourced from O[Y_WIDTH]. #29

Closed litghost closed 5 years ago

litghost commented 5 years ago

Previous logic was using CO[Y_WIDTH], which is downstream of another MUXCY. Rather than using CO[Y_WIDTH], O[Y_WIDTH] with S[Y_WIDTH] = 0 works just as well.

For reference:

O[N] = CO[N-1] ^ S[N]

So if S[N] = 0, O[N] === CO[N-1], which is the desired state.

Signed-off-by: Keith Rothman 537074+litghost@users.noreply.github.com

litghost commented 5 years ago

Are there any tests for this?

Tests added.