replace the block description list with references
diff --git a/user_guide.rst b/user_guide.rst
index 16b3234..de3ff4a 100644
--- a/user_guide.rst
+++ b/user_guide.rst
@@ -204,11 +204,6 @@
Block Architecture Overview
---------------------------
-The following sections describe each of the blocks in detail:
-
-.. contents:: :local:
- :depth: 1
-
Block Description
~~~~~~~~~~~~~~~~~
@@ -221,9 +216,24 @@
and a special I/O (:cell:`sky130_fd_io__sio`), a reference generator (:cell:`sky130_fd_io__refgen`) for providing voltage references to the :cell:`sky130_fd_io__sio` and Power and Ground (PG)
cells that make up the I/O ring.
+The following sections describe each of the blocks in detail:
+
A single table comparison of all features across different IO's is provided in :numref:`io features comparison`.
-.. io-common-features_
+
+* I/O [1]_ Common Features, section :ref:`io-common-features`.
+* :cell:`sky130_fd_io__gpio`, :cell:`sky130_fd_io__gpiosf` Additional Features, section :ref:`sky130_fd_io__gpio-additional-features`.
+* :cell:`sky130_fd_io__gpiov2` Additional Features, section :ref:`sky130_fd_io__gpiov2-additional-features`.
+* :cell:`sky130_fd_io__gpio_ovtv2` Additional Features, section :ref:`sky130_fd_io__gpio_ovtv2-additional-features`.
+* :cell:`sky130_fd_io__sio` Additional Features, :ref:`sky130_fd_io__sio-additional-features`.
+* :cell:`sky130_fd_io__refgen` Features, :ref:`sky130_fd_io__refgen-features`.
+* PG pads (ESD), :ref:`pg-pads`.
+* Overlay Cells, :ref:`overlay-cells`.
+* Power Detectors, :ref:`power-detector`.
+
+
+
+.. _io-common-features:
I/O\ [1]_ Common Features
~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -468,6 +478,7 @@
- Latched means that the input and output enable are latched. This is the same functionality as mentioned in :numref:`io vil vih`.
- Normal refers any mode other than Sleep modes
+.. _sky130_fd_io__gpio-additional-features:
:cell:`sky130_fd_io__gpio` Additional Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -617,6 +628,7 @@
``tie_hi_esd``).
All other :cell:`sky130_fd_io__gpio` cells have their input buffers disabled while XRES is asserted (``enable_inp_h`` is ``tie_lo_esd``).
+.. _sky130_fd_io__gpiov2-additional-features:
:cell:`sky130_fd_io__gpiov2` Additional Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -733,7 +745,7 @@
| | | | | | | * WPD Mode |
+---------+----------+------+-------------------+-------------------+---------------------+---------------------------+
-
+.. _sky130_fd_io__gpio_ovtv2-additional-features:
:cell:`sky130_fd_io__gpio_ovtv2` Additional Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -849,6 +861,7 @@
| | | | | | | * WPD Mode |
+-------+----------+------+--------------+-------------------+-------------------------------------------+---------------+
+.. _sky130_fd_io__sio-additional-features:
:cell:`sky130_fd_io__sio` Additional Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -960,6 +973,7 @@
Notice that the input buffer and output buffer configurations can be selected independently.
For example, the standard single-ended input buffer and the regulated output buffer can be selected.
+.. _sky130_fd_io__refgen-features:
:cell:`sky130_fd_io__refgen` (Reference Generator) Features
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1212,6 +1226,7 @@
two amuxbus's.
When connecting ``amux_a_l`` and ``amux_a_r`` care must be taken to disconnect the mid-node and then close the right and left switch.
+.. _pg-pads:
PG pads (ESD)
~~~~~~~~~~~~~
@@ -1459,6 +1474,7 @@
| Hi-Z | Hi-Z |
+------+-------------+
+.. _overlay-cells:
Overlay Cells
~~~~~~~~~~~~~
@@ -1523,7 +1539,8 @@
| 11 | :cell:`sky130_fd_io__overlay_vssd_hvc` | :cell:`sky130_fd_io__top_ground_hvc_wpad` | VSSD power pad | HV ESD clamp |
+------+-----------------------------------------+-------------------------------------------+-----------------+------------------+
-Power detector
+.. _power-detector:
+Power Detector
~~~~~~~~~~~~~~
This cell is developed to detect vddd and vddio power supplies and to level shift the hv control signals across vddio<->vddd voltage domains.
