diff --git a/docs/source/manual/arch_lang/circuit_library.rst b/docs/source/manual/arch_lang/circuit_library.rst
index 59e5f055f..e19e3aec5 100644
--- a/docs/source/manual/arch_lang/circuit_library.rst
+++ b/docs/source/manual/arch_lang/circuit_library.rst
@@ -143,7 +143,8 @@ A circuit model may consist of a number of ports. The port list is mandatory in
 
 .. option:: <port type="<string>" prefix="<string>" lib_name="<string>" size="<int>"
   default_val="<int>" circuit_model_name="<string>" mode_select="<bool>"
-  is_global="<bool>" is_set="<bool>" is_reset="<bool>" is_config_enable="<bool>"/>
+  is_global="<bool>" is_set="<bool>" is_reset="<bool>" 
+  is_config_enable="<bool>" is_io="<bool>" is_data_io="<bool>"/>
 
   Define the attributes for a port of a circuit model.
 
@@ -169,10 +170,12 @@ A circuit model may consist of a number of ports. The port list is mandatory in
 
     .. note:: ``circuit_model_name`` is only valid when the type of this port is ``sram``.
 
-  - ``io="true|false"`` Specify if this port should be treated as an I/O port of an FPGA fabric. When this is enabled, this port of each circuit model instanciated in FPGA will be added as an I/O of an FPGA.
+  - ``is_io="true|false"`` Specify if this port should be treated as an I/O port of an FPGA fabric. When this is enabled, this port of each circuit model instanciated in FPGA will be added as an I/O of an FPGA.
 
     .. note:: global ``output`` ports must be ``io`` ports
 
+  - ``is_data_io="true|false"`` Specify if this port should be treated as a mappable FPGA I/O port for users' implementation. When this is enabled, I/Os of user's implementation, e.g., ``.input`` and ``.output`` in ``.blif`` netlist, can be mapped to the port through VPR.
+
   - ``mode_select="true|false"`` Specify if this port controls the mode switching in a configurable logic block. This is due to that a configurable logic block can operate in different modes, which is controlled by SRAM bits.
 
     .. note:: ``mode_select`` is only valid when the type of this port is ``sram``.