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authorEddie Hung <eddie@fpgeh.com>2019-08-22 11:52:24 -0700
committerEddie Hung <eddie@fpgeh.com>2019-08-22 11:52:24 -0700
commit6e8fda8bf074ca14c5bd58c0dbafc3a5c8ec8e7f (patch)
treeedad05cc9930d696fd55e74c813a7fcb165d0d24 /passes
parentcabadb85e2520bd07fa5071d553235da3614b462 (diff)
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Add doc
Diffstat (limited to 'passes')
-rw-r--r--passes/pmgen/xilinx_srl.cc15
1 files changed, 14 insertions, 1 deletions
diff --git a/passes/pmgen/xilinx_srl.cc b/passes/pmgen/xilinx_srl.cc
index 45a78a320..22fb93e18 100644
--- a/passes/pmgen/xilinx_srl.cc
+++ b/passes/pmgen/xilinx_srl.cc
@@ -168,7 +168,20 @@ struct XilinxSrlPass : public Pass {
log("\n");
log(" xilinx_srl [options] [selection]\n");
log("\n");
- log("TODO.\n");
+ log("This pass converts chains of built-in flops ($_DFF_[NP]_, $_DFFE_*) as well as\n");
+ log("Xilinx flops (FDRE, FDRE_1) into a $__XILINX_SHREG cell. Chains must be of the\n");
+ log("same type, clock, clock polarity, enable, enable polarity (when relevant).\n");
+ log("Flops with resets cannot be mapped to Xilinx devices and will not be inferred.");
+ log("\n");
+ log(" -minlen N\n");
+ log(" min length of shift register (default = 3)\n");
+ log("\n");
+ log(" -fixed\n");
+ log(" infer fixed-length shift registers.\n");
+ log("\n");
+ log(" -variable\n");
+ log(" infer variable-length shift registers (i.e. fixed-length shifts where\n");
+ log(" each element also fans-out to a $shiftx cell.\n");
log("\n");
}