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Move the last presentation slides

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Krystine Sherwin 2023-08-08 09:50:36 +12:00
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62
docs/source/using_yosys/more_scripting/selections.rst
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@ -199,15 +199,22 @@ tools).
of the circuit.
- :doc:`/cmd/show`.
- :doc:`/cmd/dump`.
- :doc:`/cmd/add` and :doc:`/cmd/delete` can be used to modify and reorganize a
design dynamically.
Reorganizing a module
^^^^^^^^^^^^^^^^^^^^^
Changing design hierarchy
^^^^^^^^^^^^^^^^^^^^^^^^^
Commands such as ``flatten`` and ``submod`` can be used to change the design
hierarchy, i.e. flatten the hierarchy or moving parts of a module to a
submodule. This has applications in synthesis scripts as well as in reverse
engineering and analysis. An example using ``submod`` is shown below for
reorganizing a module in Yosys and checking the resulting circuit.
.. literalinclude:: ../../../resources/PRESENTATION_ExOth/scrambler.v
:language: verilog
:caption: ``docs/resources/PRESENTATION_ExOth/scrambler.v``
.. code:: yoscrypt
read_verilog scrambler.v
@ -225,15 +232,10 @@ Reorganizing a module
.. figure:: ../../../images/res/PRESENTATION_ExOth/scrambler_p02.*
:class: width-helper
Analysis of circuit behavior
^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Analyzing the resulting circuit with :doc:`/cmd/eval`:
.. code:: text
> read_verilog scrambler.v
> hierarchy; proc;; cd scrambler
> submod -name xorshift32 xs %c %ci %D %c %ci:+[D] %D %ci*:-$dff xs %co %ci %d
> cd xorshift32
> rename n2 in
> rename n1 out
@ -249,3 +251,45 @@ Analysis of circuit behavior
-------------------- ---------- ---------- -------------------------------------
\in 745495504 2c6f5bd0 00101100011011110101101111010000
\out 632435482 25b2331a 00100101101100100011001100011010
Behavioral changes
^^^^^^^^^^^^^^^^^^
Commands such as ``techmap`` can be used to make behavioral changes to the
design, for example changing asynchronous resets to synchronous resets. This has
applications in design space exploration (evaluation of various architectures
for one circuit).
The following techmap map file replaces all positive-edge async reset flip-flops
with positive-edge sync reset flip-flops. The code is taken from the example
Yosys script for ASIC synthesis of the Amber ARMv2 CPU.
.. code:: verilog
(* techmap_celltype = "$adff" *)
module adff2dff (CLK, ARST, D, Q);
parameter WIDTH = 1;
parameter CLK_POLARITY = 1;
parameter ARST_POLARITY = 1;
parameter ARST_VALUE = 0;
input CLK, ARST;
input [WIDTH-1:0] D;
output reg [WIDTH-1:0] Q;
wire [1023:0] _TECHMAP_DO_ = "proc";
wire _TECHMAP_FAIL_ = !CLK_POLARITY || !ARST_POLARITY;
always @(posedge CLK)
if (ARST)
Q <= ARST_VALUE;
else
<= D;
endmodule
For more on the ``techmap`` command, see the page on
:doc:`/yosys_internals/techmap` or the
:doc:`techmap command reference document</cmd/techmap>`.