diff --git a/ecp5/arch.cc b/ecp5/arch.cc
index d2d62241..4a3e8ef3 100644
--- a/ecp5/arch.cc
+++ b/ecp5/arch.cc
@@ -500,6 +500,12 @@ IdString Arch::getPortClock(const CellInfo *cell, IdString port) const { return
 
 bool Arch::isClockPort(const CellInfo *cell, IdString port) const { return false; }
 
+bool Arch::isIOCell(const CellInfo *cell) const
+{
+    return cell->type == id("TRELLIS_IO");
+}
+
+
 std::vector<std::pair<std::string, std::string>> Arch::getTilesAtLocation(int row, int col)
 {
     std::vector<std::pair<std::string, std::string>> ret;
diff --git a/ecp5/arch.h b/ecp5/arch.h
index e00e111a..fd8d0a13 100644
--- a/ecp5/arch.h
+++ b/ecp5/arch.h
@@ -833,6 +833,8 @@ struct Arch : BaseCtx
     bool isClockPort(const CellInfo *cell, IdString port) const;
     // Return true if a port is a net
     bool isGlobalNet(const NetInfo *net) const;
+    // Return true if a cell is an IO
+    bool isIOCell(const CellInfo *cell) const;
 
     // -------------------------------------------------
     // Placement validity checks
diff --git a/generic/arch.h b/generic/arch.h
index 59fe8d05..e7010885 100644
--- a/generic/arch.h
+++ b/generic/arch.h
@@ -215,6 +215,8 @@ struct Arch : BaseCtx
     bool getCellDelay(const CellInfo *cell, IdString fromPort, IdString toPort, DelayInfo &delay) const;
     IdString getPortClock(const CellInfo *cell, IdString port) const;
     bool isClockPort(const CellInfo *cell, IdString port) const;
+    // Return true if a cell is an IO
+    bool isIOCell(const CellInfo *cell) const;
 
     bool isValidBelForCell(CellInfo *cell, BelId bel) const;
     bool isBelLocationValid(BelId bel) const;