diff --git a/supervisor/session/rtu.lua b/supervisor/session/rtu.lua
index 4f04a1e..dea4eb2 100644
--- a/supervisor/session/rtu.lua
+++ b/supervisor/session/rtu.lua
@@ -140,13 +140,15 @@ function rtu.new_session(id, s_addr, i_seq_num, in_queue, out_queue, timeout, ad
 
                         -- link this to any subsystems this RTU provides connections for
                         if type(unit) ~= "nil" then
-                            for assignment, _ in pairs(unit_advert.rs_conns) do
-                                if assignment == 0 then
-                                    facility.add_redstone(unit)
-                                elseif assignment > 0 and assignment < #self.fac_units then
-                                    self.fac_units[assignment].add_redstone(unit)
-                                else
-                                    log.warning(util.c(log_tag, "_handle_advertisement(): unrecognized redstone RTU assignment ", assignment, " ", type_string))
+                            for assignment, conns in pairs(unit_advert.rs_conns) do
+                                if #conns > 0 then
+                                    if assignment == 0 then
+                                        facility.add_redstone(unit)
+                                    elseif assignment > 0 and assignment <= #self.fac_units then
+                                        self.fac_units[assignment].add_redstone(unit)
+                                    else
+                                        log.warning(util.c(log_tag, "_handle_advertisement(): unrecognized redstone RTU assignment ", assignment, " ", type_string))
+                                    end
                                 end
                             end
                         end
diff --git a/supervisor/session/rtu/redstone.lua b/supervisor/session/rtu/redstone.lua
index 7b91dc3..2cd2856 100644
--- a/supervisor/session/rtu/redstone.lua
+++ b/supervisor/session/rtu/redstone.lua
@@ -127,7 +127,7 @@ function redstone.new(session_id, unit_id, advert, out_queue)
                         write = function () end
                     }
 
-                    self.db.io[port] = io_f
+                    self.db.io[bank][port] = io_f
                 elseif mode == IO_MODE.DIGITAL_OUT then
                     self.has_do = true
                     table.insert(self.io_map.digital_out, io_entry)
@@ -145,7 +145,7 @@ function redstone.new(session_id, unit_id, advert, out_queue)
                         end
                     }
 
-                    self.db.io[port] = io_f
+                    self.db.io[bank][port] = io_f
                 elseif mode == IO_MODE.ANALOG_IN then
                     self.has_ai = true
                     table.insert(self.io_map.analog_in, io_entry)
@@ -160,7 +160,7 @@ function redstone.new(session_id, unit_id, advert, out_queue)
                         write = function () end
                     }
 
-                    self.db.io[port] = io_f
+                    self.db.io[bank][port] = io_f
                 elseif mode == IO_MODE.ANALOG_OUT then
                     self.has_ao = true
                     table.insert(self.io_map.analog_out, io_entry)
@@ -180,7 +180,7 @@ function redstone.new(session_id, unit_id, advert, out_queue)
                         end
                     }
 
-                    self.db.io[port] = io_f
+                    self.db.io[bank][port] = io_f
                 else
                     -- should be unreachable code, we already validated ports
                     log.error(util.c(log_tag, "failed to identify advertisement port IO mode (", bank, ":", port, ")"), true)
@@ -396,9 +396,10 @@ function redstone.new(session_id, unit_id, advert, out_queue)
         self.session.post_update()
     end
 
-    -- invalidate build cache
+    -- force a re-read of cached outputs
     function public.invalidate_cache()
-        -- no build cache for this device
+        _read_coils()
+        _read_holding_registers()
     end
 
     -- get the unit session database