diff --git a/fpga_architecture.xsd b/fpga_architecture.xsd
index 6d93afd..a1511ea 100644
--- a/fpga_architecture.xsd
+++ b/fpga_architecture.xsd
@@ -293,31 +293,50 @@
     </xs:restriction>
   </xs:simpleType>
 
-  <xs:simpleType name="pb_io_equivalent">
-    <xs:restriction base="xs:string">
+  <xs:simpleType name="pb_input_equivalent">
+     <xs:restriction base="xs:string">
       <xs:enumeration value="none"/>
       <xs:enumeration value="full"/>
       <xs:enumeration value="instance"/>
-      <xs:enumeration value="false"/>
-      <xs:enumeration value="true"/>
     </xs:restriction>
   </xs:simpleType>
 
   <xs:complexType name="pb_type_input">
     <xs:attribute name="name" type="xs:string" use="required"/>
+    <xs:attribute name="equivalent" type="pb_input_equivalent" default="none"/>
     <xs:attribute name="num_pins" type="xs:int" use="required"/>
-    <xs:attribute name="equivalent" type="pb_io_equivalent" default="false"/>
     <xs:attribute name="is_non_clock_global" type="xs:boolean"/>
     <xs:attribute name="port_class" type="xs:string" />
   </xs:complexType>
 
+  <xs:simpleType name="pb_output_equivalent">
+     <xs:restriction base="xs:string">
+      <xs:enumeration value="none"/>
+      <xs:enumeration value="full"/>
+    </xs:restriction>
+  </xs:simpleType>
+
   <xs:complexType name="pb_type_output">
     <xs:attribute name="name" type="xs:string" use="required"/>
+    <xs:attribute name="equivalent" type="pb_output_equivalent" default="none"/>
     <xs:attribute name="num_pins" type="xs:int" use="required"/>
-    <xs:attribute name="equivalent" type="pb_io_equivalent" default="false"/>
     <xs:attribute name="port_class" type="xs:string" />
   </xs:complexType>
 
+  <xs:simpleType name="pb_clock_equivalent">
+     <xs:restriction base="xs:string">
+      <xs:enumeration value="none"/>
+      <xs:enumeration value="full"/>
+      <xs:enumeration value="instance"/>
+    </xs:restriction>
+  </xs:simpleType>
+
+  <xs:complexType name="pb_type_clock">
+    <xs:attribute name="name" type="xs:string" use="required"/>
+    <xs:attribute name="equivalent" type="pb_clock_equivalent" default="none"/>
+    <xs:attribute name="num_pins" type="xs:int" use="required"/>
+  </xs:complexType>
+
   <xs:simpleType name="delay_matrix_type">
     <xs:restriction base="xs:string">
       <xs:enumeration value="min"/>
@@ -567,7 +586,7 @@
       <xs:element name="pb_type" type="pb_type"/>
       <xs:element name="input" type="pb_type_input"/>
       <xs:element name="output" type="pb_type_output"/>
-      <xs:element name="clock" type="pb_type_output"/>
+      <xs:element name="clock" type="pb_type_clock"/>
       <xs:element name="metadata" type="metadata"/>
       <xs:element name="mode" type="mode"/>
       <xs:element name="interconnect" type="interconnect"/>
@@ -775,4 +794,4 @@
     </xs:complexType>
   </xs:element>
 
-</xs:schema>
\ No newline at end of file
+</xs:schema>