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Diffstat (limited to 'README.md')
| -rw-r--r-- | README.md | 30 |
1 files changed, 20 insertions, 10 deletions
@@ -257,13 +257,9 @@ for them: - Non-synthesizable language features as defined in IEC 62142(E):2005 / IEEE Std. 1364.1(E):2002 -- The ``tri``, ``triand``, ``trior``, ``wand`` and ``wor`` net types +- The ``tri``, ``triand`` and ``trior`` net types -- The ``config`` keyword and library map files - -- The ``disable``, ``primitive`` and ``specify`` statements - -- Latched logic (is synthesized as logic with feedback loops) +- The ``config`` and ``disable`` keywords and library map files Verilog Attributes and non-standard features @@ -354,6 +350,14 @@ Verilog Attributes and non-standard features through the synthesis. When entities are combined, a new |-separated string is created that contains all the string from the original entities. +- The ``defaultvalue`` attribute is used to store default values for + module inputs. The attribute is attached to the input wire by the HDL + front-end when the input is declared with a default value. + +- The ``parameter`` and ``localparam`` attributes are used to mark wires + that represent module parameters or localparams (when the HDL front-end + is run in -pwires mode). + - In addition to the ``(* ... *)`` attribute syntax, Yosys supports the non-standard ``{* ... *}`` attribute syntax to set default attributes for everything that comes after the ``{* ... *}`` statement. (Reset @@ -417,12 +421,18 @@ Verilog Attributes and non-standard features $ yosys -p 'plugin -a foo -i /lib/libm.so; read_verilog dpitest.v' - Sized constants (the syntax ``<size>'s?[bodh]<value>``) support constant - expressions as <size>. If the expression is not a simple identifier, it + expressions as ``<size>``. If the expression is not a simple identifier, it must be put in parentheses. Examples: ``WIDTH'd42``, ``(4+2)'b101010`` -- The system tasks ``$finish`` and ``$display`` are supported in initial blocks - in an unconditional context (only if/case statements on parameters - and constant values). The intended use for this is synthesis-time DRC. +- The system tasks ``$finish``, ``$stop`` and ``$display`` are supported in + initial blocks in an unconditional context (only if/case statements on + expressions over parameters and constant values are allowed). The intended + use for this is synthesis-time DRC. + +- There is limited support for converting specify .. endspecify statements to + special ``$specify2``, ``$specify3``, and ``$specrule`` cells, for use in + blackboxes and whiteboxes. Use ``read_verilog -specify`` to enable this + functionality. (By default specify .. endspecify blocks are ignored.) Non-standard or SystemVerilog features for formal verification |