diff --git a/nexus/arch.h b/nexus/arch.h
index f787c2b3..29acc5f5 100644
--- a/nexus/arch.h
+++ b/nexus/arch.h
@@ -1271,6 +1271,18 @@ struct Arch : BaseCtx
         int wire = pip_data(pip).to_wire;
         return db->loctypes[chip_info->grid[pip.tile].loc_type].wires[wire].name;
     }
+
+    // -------------------------------------------------
+
+    // Get a map cell type -> pins that can be inverted
+    void get_invertible_pins(std::unordered_map<IdString, std::unordered_set<IdString>> &pins) const;
+    // Get a map cell -> pin -> value _it takes_ if disconnected
+    void get_pins_floating_value(std::unordered_map<IdString, std::unordered_map<IdString, bool>> &pins) const;
+    // Get a map cell -> pin -> value _it must be connected to_ if disconnected
+    // Default value for all pins, if not specified is 0
+    void
+    get_pins_default_value(std::unordered_map<IdString, std::unordered_map<IdString, Property::State>> &pins) const;
+
     // -------------------------------------------------
 
     NeighWireRange neigh_wire_range(WireId wire) const
diff --git a/nexus/pack.cc b/nexus/pack.cc
index 5a18f6d4..c1e3664f 100644
--- a/nexus/pack.cc
+++ b/nexus/pack.cc
@@ -40,6 +40,7 @@ struct NexusPacker
         std::unordered_map<IdString, IdString> param_xform;
         std::vector<std::pair<IdString, std::string>> set_attrs;
         std::vector<std::pair<IdString, Property>> set_params;
+        std::vector<std::pair<IdString, Property>> default_params;
     };
 
     void xform_cell(const std::unordered_map<IdString, XFormRule> &rules, CellInfo *ci)
@@ -87,6 +88,10 @@ struct NexusPacker
         for (auto &attr : rule.set_attrs)
             ci->attrs[attr.first] = attr.second;
 
+        for (auto &param : rule.default_params)
+            if (!ci->params.count(param.first))
+                ci->params[param.first] = param.second;
+
         for (auto &param : rule.set_params)
             ci->params[param.first] = param.second;
     }
@@ -134,6 +139,11 @@ struct NexusPacker
             ff_rules[type].port_xform[id_D] = id_M; // will be rerouted to DI later if applicable
             ff_rules[type].port_xform[id_SP] = id_CE;
             ff_rules[type].port_xform[id_Q] = id_Q;
+
+            ff_rules[id_FD1P3BX].default_params.emplace_back(id_CLKMUX, std::string("CLK"));
+            ff_rules[id_FD1P3BX].default_params.emplace_back(id_CEMUX, std::string("CE"));
+            ff_rules[id_FD1P3BX].default_params.emplace_back(id_LSRMUX, std::string("LSR"));
+            ff_rules[id_FD1P3BX].set_params.emplace_back(id_LSRMODE, std::string("LSR"));
         }
         // Async preload
         ff_rules[id_FD1P3BX].set_params.emplace_back(id_SRMODE, std::string("ASYNC"));
diff --git a/nexus/pins.cc b/nexus/pins.cc
new file mode 100644
index 00000000..5627f557
--- /dev/null
+++ b/nexus/pins.cc
@@ -0,0 +1,53 @@
+/*
+ *  nextpnr -- Next Generation Place and Route
+ *
+ *  Copyright (C) 2020  David Shah <dave@ds0.me>
+ *
+ *
+ *  Permission to use, copy, modify, and/or distribute this software for any
+ *  purpose with or without fee is hereby granted, provided that the above
+ *  copyright notice and this permission notice appear in all copies.
+ *
+ *  THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ *  WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ *  MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ *  ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ *  WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ *  ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ *  OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ *
+ */
+
+#include "nextpnr.h"
+
+NEXTPNR_NAMESPACE_BEGIN
+
+void Arch::get_invertible_pins(std::unordered_map<IdString, std::unordered_set<IdString>> &pins) const
+{
+    pins[id_OXIDE_FF] = {id_CLK, id_LSR, id_CE};
+    pins[id_RAMW] = {id_WCK};
+    pins[id_SEIO18_CORE] = {id_T};
+    pins[id_SEIO33_CORE] = {id_T};
+}
+
+void Arch::get_pins_floating_value(std::unordered_map<IdString, std::unordered_map<IdString, bool>> &pins) const
+{
+    pins[id_OXIDE_COMB] = {{id_A, true}, {id_B, true}, {id_C, true}, {id_D, true}, {id_SEL, true}};
+    pins[id_OXIDE_FF] = {{id_CLK, false}, {id_LSR, true}, {id_CE, true}};
+    pins[id_SEIO18_CORE] = {{id_T, true}};
+    pins[id_SEIO33_CORE] = {{id_T, true}};
+}
+
+void Arch::get_pins_default_value(
+        std::unordered_map<IdString, std::unordered_map<IdString, Property::State>> &pins) const
+{
+    pins[id_OXIDE_COMB] = {{id_A, Property::S1},    {id_B, Property::S1},    {id_C, Property::S1},
+                           {id_D, Property::S1},    {id_SEL, Property::S1},  {id_WAD0, Property::Sx},
+                           {id_WAD1, Property::Sx}, {id_WAD2, Property::Sx}, {id_WAD3, Property::Sx},
+                           {id_WCK, Property::Sx},  {id_WRE, Property::Sx},  {id_WD, Property::Sx}};
+    pins[id_OXIDE_FF] = {{id_CE, Property::S1}, {id_DI, Property::Sx}};
+    pins[id_SEIO18_CORE] = {{id_T, Property::S1}};
+    pins[id_SEIO33_CORE] = {{id_T, Property::S1}};
+}
+
+NEXTPNR_NAMESPACE_END
\ No newline at end of file