doc: vpr: cmd: add info on unconnected ports handling in verilog netlist

Signed-off-by: Pawel Czarnecki <[email protected]>

Author: lpawelcz

doc/src/vpr/command_line_usage.rst

@@ -1237,6 +1237,28 @@ Analysis Options
 
     **Default:** ``off``
 
+.. option:: --post_synth_netlist_unconn_inputs { unconnected | nets | gnd | vcc }
+
+    Controls how unconnected input cell ports are handled in the post-synthesis netlist
+      * unconnected: leave unconnected
+      * nets: connect each unconnected input pin to its own separate
+              undriven net named: __vpr__unconn<ID>, where <ID> is index
+              assigned to this occurrence of unconnected port in design
+      * gnd: tie all to ground (1'b0)
+      * vcc: tie all to VCC (1'b1)
+
+    **Default:** ``unconnected``
+
+.. option:: --post_synth_netlist_unconn_outputs { unconnected | nets }
+
+    Controls how unconnected output cell ports are handled in the post-synthesis netlist
+      * unconnected: leave unconnected
+      * nets: connect each unconnected output pin to its own separate
+              undriven net named: __vpr__unconn<ID>, where <ID> is index
+              assigned to this occurrence of unconnected port in design
+
+    **Default:** ``unconnected``
+
 .. option:: --timing_report_npaths <int>
 
     Controls how many timing paths are reported.