diff --git a/ARCH/openfpga_arch_template/k4_frac_N8_register_scan_chain_caravel_io_skywater130nm_fdhd_cc_openfpga.xml b/ARCH/openfpga_arch_template/k4_frac_N8_register_scan_chain_caravel_io_skywater130nm_fdhd_cc_openfpga.xml
index e85ac4a..50a67de 100644
--- a/ARCH/openfpga_arch_template/k4_frac_N8_register_scan_chain_caravel_io_skywater130nm_fdhd_cc_openfpga.xml
+++ b/ARCH/openfpga_arch_template/k4_frac_N8_register_scan_chain_caravel_io_skywater130nm_fdhd_cc_openfpga.xml
@@ -221,6 +221,7 @@
   <pb_type_annotations>
     <!-- physical pb_type binding in complex block IO -->
     <pb_type name="io" physical_mode_name="physical" idle_mode_name="inpad"/>
+    <!-- IMPORTANT: must set unused I/Os to operating in INPUT mode !!! -->
     <pb_type name="io[physical].iopad" circuit_model_name="EMBEDDED_IO_HD" mode_bits="1"/> 
     <pb_type name="io[inpad].inpad" physical_pb_type_name="io[physical].iopad" mode_bits="1"/> 
     <pb_type name="io[outpad].outpad" physical_pb_type_name="io[physical].iopad" mode_bits="0"/>