SOFA/DOC/source/datasheet/sofa_chd/sofa_chd_timing.rst

.. _sofa_chd_timing:

Timing Annotation
-----------------

.. _sofa_chd_timing_clb:

Configurable Logic Block
^^^^^^^^^^^^^^^^^^^^^^^^

The path delays in :numref:`fig_sofa_chd_fle_arch_timing` are listed in :numref:`table_sofa_chd_fle_arch_timing`.

.. _fig_sofa_chd_fle_arch_timing:

.. figure:: ./figures/sofa_chd_fle_arch_timing.svg
  :scale: 30%
  :alt: Schematic of a logic element used in SOFA CHD FPGA

  Schematic of a logic element used in SOFA CHD FPGA

.. _table_sofa_chd_fle_arch_timing:

.. table:: Path delays of logic element in the SOFA CHD FPGA

  +-------------------------+------------------------------+
  | Path / Delay            | TT (unit: ns)                |
  +=========================+==============================+
  | in0 -> LUT3_out[0] [1]_ | 2.31                         |
  +-------------------------+------------------------------+
  | in1 -> LUT3_out[0] [1]_ | 2.31                         |
  +-------------------------+------------------------------+
  | in2 -> LUT3_out[0] [1]_ | 2.31                         |
  +-------------------------+------------------------------+
  | in0 -> LUT3_out[1] [1]_ | 2.31                         |
  +-------------------------+------------------------------+
  | in1 -> LUT3_out[1] [1]_ | 2.31                         |
  +-------------------------+------------------------------+
  | in2 -> LUT3_out[1] [1]_ | 2.31                         |
  +-------------------------+------------------------------+
  | in0 -> LUT4_out [1]_    | 2.60                         |
  +-------------------------+------------------------------+
  | in1 -> LUT4_out [1]_    | 2.60                         |
  +-------------------------+------------------------------+
  | in2 -> LUT4_out [1]_    | 2.60                         |
  +-------------------------+------------------------------+
  | in3 -> LUT4_out [1]_    | 2.60                         |
  +-------------------------+------------------------------+
  | LUT3_out[0] -> A        | 0.56                         |
  +-------------------------+------------------------------+
  | LUT4_out[0] -> A        | 0.58                         |
  +-------------------------+------------------------------+
  | A -> out[0]             | 0.88                         |
  +-------------------------+------------------------------+
  | A -> FF[0]              | 0.56                         |
  +-------------------------+------------------------------+
  | FF[0] -> out[0]         | 0.88                         |
  +-------------------------+------------------------------+
  | LUT3_out[1] -> out[1]   | 0.89                         |
  +-------------------------+------------------------------+
  | LUT3_out[1] -> FF[1]    | 0.56                         |
  +-------------------------+------------------------------+
  | FF[1] -> out[1]         | 0.89                         |
  +-------------------------+------------------------------+
  | regin -> FF[0]          | 0.58                         |
  +-------------------------+------------------------------+
  | FF[0] -> FF[1]          | 0.56                         |
  +-------------------------+------------------------------+

.. [1] The LUT input-to-output delay should be different as some inputs are close to output. However, we consider a uniform path delay considering the delay from the farest input ``in[0]`` to output. This is because VPR currently does not have LUT rebalancing techniques.

.. _sofa_chd_timing_io:

I/O Block
^^^^^^^^^

The path delays of I/O blocks in SOFA CHD FPGA is same as the SOFA HD FPGA. See details in :ref:`sofa_hd_timing_io`. 

.. _sofa_chd_timing_routing:

Routing Architecture
^^^^^^^^^^^^^^^^^^^^

The path delays in :numref:`fig_sofa_hd_routing_arch` are listed in :numref:`table_sofa_chd_routing_arch_timing`.

.. _table_sofa_chd_routing_arch_timing:

.. table:: Path delays of routing blocks in the SOFA CHD FPGA

  +---------------------------+------------------------------+
  | Path / Delay              | TT (unit: ns)                |
  +===========================+==============================+
  | A -> B                    | 1.44                         |
  +---------------------------+------------------------------+
  | A -> C                    | 1.44                         |
  +---------------------------+------------------------------+
  | A -> D                    | 1.44                         |
  +---------------------------+------------------------------+
  | B -> E                    | 1.38                         |
  +---------------------------+------------------------------+