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| author | Eddie Hung <eddie@fpgeh.com> | 2019-09-26 14:31:02 -0700 |
|---|---|---|
| committer | Eddie Hung <eddie@fpgeh.com> | 2019-09-26 14:31:02 -0700 |
| commit | 26657037b8de3cf09bafb2bca3940515dad96222 (patch) | |
| tree | 19d210112815d097852579691d0840ceb8a0c588 /passes/pmgen/xilinx_dsp.cc | |
| parent | 5b9deef10df2ab958112f6ff55f27776e492f187 (diff) | |
| download | yosys-26657037b8de3cf09bafb2bca3940515dad96222.tar.gz yosys-26657037b8de3cf09bafb2bca3940515dad96222.tar.bz2 yosys-26657037b8de3cf09bafb2bca3940515dad96222.zip | |
Update doc with max cascade chain of 20
Diffstat (limited to 'passes/pmgen/xilinx_dsp.cc')
| -rw-r--r-- | passes/pmgen/xilinx_dsp.cc | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/passes/pmgen/xilinx_dsp.cc b/passes/pmgen/xilinx_dsp.cc index 6ce5f2e16..11c7e5ea8 100644 --- a/passes/pmgen/xilinx_dsp.cc +++ b/passes/pmgen/xilinx_dsp.cc @@ -576,8 +576,10 @@ struct XilinxDspPass : public Pass { log("Use of the dedicated 'PCOUT' -> 'PCIN' cascade path is detected for 'P' -> 'C'\n"); log("connections (optionally, where 'P' is right-shifted by 17-bits and used as an\n"); log("input to the post-adder -- a pattern common for summing partial products to\n"); - log("implement wide multipliers). Initial support also exists for similar cascading\n"); - log("for AREG and BREG using '[AB]OUT' -> '[AB]IN'.\n"); + log("implement wide multipliers). Limited support also exists for similar cascading\n"); + log("for A and B using '[AB]COUT' -> '[AB]CIN'. Currently, cascade chains are limited\n"); + log("to a maximum length of 20 cells, corresponding to the smallest Xilinx 7 Series\n"); + log("device.\n"); log("\n"); log("\n"); log("Experimental feature: addition/subtractions less than 12 or 24 bits with the\n"); |