Add tests/various/chparam.sh

[yosys.git] / README.md

diff --git a/README.md b/README.md
index 45577ade23c00d323fc718fe6e0d9faabcef9965..913777f2ee463933d82573fc6de33aed488e8447 100644 (file)
--- a/README.md
+++ b/README.md
@@ -311,12 +311,24 @@ Verilog Attributes and non-standard features
   that have the same ports as the real thing but do not contain information
   on the internal configuration. This modules are only used by the synthesis
   passes to identify input and output ports of cells. The Verilog backend
-  also does not output blackbox modules on default.
+  also does not output blackbox modules on default. ``read_verilog``, unless
+  called with ``-noblackbox`` will automatically set the blackbox attribute
+  on any empty module it reads.
 
-- The ``dynports'' attribute is used by the Verilog front-end to mark modules
+- The ``noblackbox`` attribute set on an empty module prevents ``read_verilog``
+  from automatically setting the blackbox attribute on the module.
+
+- The ``whitebox`` attribute on modules triggers the same behavior as
+  ``blackbox``, but is for whitebox modules, i.e. library modules that
+  contain a behavioral model of the cell type.
+
+- The ``lib_whitebox`` attribute overwrites ``whitebox`` when ``read_verilog``
+  is run in `-lib` mode. Otherwise it's automatically removed.
+
+- The ``dynports`` attribute is used by the Verilog front-end to mark modules
   that have ports with a width that depends on a parameter.
 
-- The ``hdlname'' attribute is used by some passes to document the original
+- The ``hdlname`` attribute is used by some passes to document the original
   (HDL) name of a module when renaming a module.
 
 - The ``keep`` attribute on cells and wires is used to mark objects that should
@@ -358,7 +370,7 @@ Verilog Attributes and non-standard features
 
 - When defining a macro with `define, all text between triple double quotes
   is interpreted as macro body, even if it contains unescaped newlines. The
-  tipple double quotes are removed from the macro body. For example:
+  triple double quotes are removed from the macro body. For example:
 
       `define MY_MACRO(a, b) """
          assign a = 23;
@@ -445,7 +457,7 @@ Non-standard or SystemVerilog features for formal verification
   supported in any clocked block.
 
 - The syntax ``@($global_clock)`` can be used to create FFs that have no
-  explicit clock input ($ff cells). The same can be achieved by using
+  explicit clock input (``$ff`` cells). The same can be achieved by using
   ``@(posedge <netname>)`` or ``@(negedge <netname>)`` when ``<netname>``
   is marked with the ``(* gclk *)`` Verilog attribute.
 
@@ -458,7 +470,7 @@ from SystemVerilog:
 
 - The ``assert`` statement from SystemVerilog is supported in its most basic
   form. In module context: ``assert property (<expression>);`` and within an
-  always block: ``assert(<expression>);``. It is transformed to a $assert cell.
+  always block: ``assert(<expression>);``. It is transformed to an ``$assert`` cell.
 
 - The ``assume``, ``restrict``, and ``cover`` statements from SystemVerilog are
   also supported. The same limitations as with the ``assert`` statement apply.