updated comments

Author: WhiteNinjaZ

doc/src/arch/reference.rst

@@ -2403,9 +2403,11 @@ The full format is documented below.
 
     :opt_param switch_override:
 
-        Specifies the name of a switch to be used to override the wire_switch of the segments in the ``to`` set. Can be used to create more complicated wire structures such as T and L shaped segments.
+        Specifies the name of a switch to be used to override the wire_switch of the segments in the ``to`` set. 
+        Can be used to create switch patterns where different switches are used for different types of connections. 
+        By using a zero-delay and zero-resistance switch one can also create T and L shaped wire segments.
 
-        **Default:** If no override is specified, the normal interconnect will be used. 
+        **Default:** If no override is specified, the usual wire_switch that drives the ``to`` wire will be used. 
 
     .. arch:tag:: <from type="string" switchpoint="int, int, int, ..."/>
 

libs/libarchfpga/src/parse_switchblocks.cpp

@@ -342,7 +342,7 @@ void read_sb_switchfuncs(pugi::xml_node Node, t_switchblock_inf* sb, const pugiu
 }
 
 static void parse_switch_override(const char* switch_override, t_wireconn_inf& wireconn, const t_arch_switch_inf* switches, int num_switches) {
-    // check to see if user did not specify a switch_override
+    // sentinel value to use default driving switch for the receiving wire type
     if (switch_override == std::string("")) {
         wireconn.switch_override_indx = DEFAULT_SWITCH; //Default
         return;

libs/libarchfpga/src/physical_types.h

@@ -1689,6 +1689,7 @@ struct t_wireconn_inf {
     SwitchPointOrder from_switchpoint_order = SwitchPointOrder::FIXED; //The desired from_switchpoint_set ordering
     SwitchPointOrder to_switchpoint_order = SwitchPointOrder::FIXED;   //The desired to_switchpoint_set ordering
     int switch_override_indx = DEFAULT_SWITCH;                         // index in switch array of the switch used to override wire_switch of the 'to' set.
+                                                                       // DEFAULT_SWITCH is a sentinel value (i.e. the usual driving switch from a wire for the receiving wire will be used)
 
     std::string num_conns_formula; /* Specifies how many connections should be made for this wireconn.
                                     *