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Diffstat (limited to 'doc/references/ImplementationOfVHDL.rst')
| -rw-r--r-- | doc/references/ImplementationOfVHDL.rst | 56 |
1 files changed, 28 insertions, 28 deletions
diff --git a/doc/references/ImplementationOfVHDL.rst b/doc/references/ImplementationOfVHDL.rst index 66246608d..4aa8b3a71 100644 --- a/doc/references/ImplementationOfVHDL.rst +++ b/doc/references/ImplementationOfVHDL.rst @@ -4,7 +4,7 @@ Implementation of VHDL *************************** -This chapter describes several implementation defined aspect of VHDL in GHDL. +This chapter describes several implementation defined aspects of VHDL in GHDL. .. _VHDL_standards: @@ -33,7 +33,7 @@ VHDL standards .. index:: v08 -This is very unfortunate, but there are many versions of the VHDL +Unfortunately, there are many versions of the VHDL language, and they aren't backward compatible. The VHDL language was first standardized in 1987 by IEEE as IEEE 1076-1987, and @@ -64,7 +64,7 @@ standard is not fully backward compatible with VHDL-93, since the type of a shared variable must now be a protected type (there was no such restriction before). -Minors corrections were added by the 2002 revision of the VHDL standard. This +Minor corrections were added by the 2002 revision of the VHDL standard. This revision is not fully backward compatible with VHDL-00 since, for example, the value of the `'instance_name` attribute has slightly changed. @@ -96,12 +96,12 @@ table below: Select VHDL-2000 standard, which adds protected types. 02 - Select VHDL-2002 standard + Select VHDL-2002 standard. 08 Select VHDL-2008 standard (partially implemented). -The 93, 93c, 00 and 02 standards are considered as compatible: you can +The 93, 93c, 00 and 02 standards are considered compatible: you can elaborate a design mixing these standards. However, 87, 93 and 08 are not compatible. @@ -121,7 +121,7 @@ with the `psl` keyword. The keyword must be followed (on the same line) by a PSL keyword such as `assert` or `default`. To continue a PSL statement on the next line, just start a new comment. -A PSL statement is considered as a process. So it is not allowed within +A PSL statement is considered a process, so it's not allowed within a process. All PSL assertions must be clocked (GHDL doesn't support unclocked assertion). @@ -135,7 +135,7 @@ You can either use a default clock like this: -- psl assert always -- a -> eventually! b; -or use a clocked expression (note the use of parenthesis): +or use a clocked expression (note the use of parentheses): .. code-block:: VHDL @@ -150,7 +150,7 @@ Source representation ===================== According to the VHDL standard, design units (i.e. entities, -architectures, packages, package bodies and configurations) may be +architectures, packages, package bodies, and configurations) may be independently analyzed. Several design units may be grouped into a design file. @@ -164,9 +164,9 @@ GHDL does not impose any restriction on the name of a design file (except that the filename may not contain any control character or spaces). -GHDL do not keep a binary representation of the design units analyzed like +GHDL does not keep a binary representation of the design units analyzed like other VHDL analyzers. The sources of the design units are re-read when -needed (for example, an entity is re-read when one of its architecture is +needed (for example, an entity is re-read when one of its architectures is analyzed). Therefore, if you delete or modify a source file of a unit analyzed, GHDL will refuse to use it. @@ -199,7 +199,7 @@ There are some restrictions on the entity being at the apex of a design hierarchy: * The generic must have a default value, and the value of a generic is its - default value; + default value. * The ports type must be constrained. Using vendor libraries @@ -230,7 +230,7 @@ Interfacing to other languages Interfacing with foreign languages is possible only on GNU/Linux systems. You can define a subprogram in a foreign language (such as `C` or -`Ada`) and import it in a VHDL design. +`Ada`) and import it into a VHDL design. Foreign declarations -------------------- @@ -264,7 +264,7 @@ subprogram and must be after it. This is a general rule for specifications. The value of the specification must be a locally static string. Even when a subprogram is foreign, its body must be present. However, since -it won't be called, you can made it empty or simply but an assertion. +it won't be called, you can make it empty or simply put an assertion. The value of the attribute must start with ``VHPIDIRECT`` (an upper-case keyword followed by one or more blanks). The linkage name of the @@ -277,24 +277,24 @@ Restrictions on foreign declarations Any subprogram can be imported. GHDL puts no restrictions on foreign subprograms. However, the representation of a type or of an interface in a -foreign language may be obscure. Most of non-composite types are easily imported: +foreign language may be obscure. Most non-composite types are easily imported: *integer types* - They are represented on a 32 bits word. This generally corresponds to + They are represented by a 32 bit word. This generally corresponds to `int` for `C` or `Integer` for `Ada`. *physical types* - They are represented on a 64 bits word. This generally corresponds to the + They are represented by a 64 bit word. This generally corresponds to the `long long` for `C` or `Long_Long_Integer` for `Ada`. *floating point types* - They are represented on a 64 bits floating point word. This generally + They are represented by a 64 bit floating point word. This generally corresponds to `double` for `C` or `Long_Float` for `Ada`. *enumeration types* - They are represented on 8 bits or 32 bits word, if the number of literals is - greater than 256. There is no corresponding C types, since arguments are + They are represented by an 8 bit word, or, if the number of literals is + greater than 256, by a 32 bit word. There is no corresponding C type, since arguments are not promoted. Non-composite types are passed by value. For the `in` mode, this @@ -310,12 +310,12 @@ to subprograms. Arrays with static bounds are represented like a `C` array, whose length is the number of elements, and are passed by reference to subprograms. -Unconstrained array are represented by a fat pointer. Do not use unconstrained +Unconstrained arrays are represented by a fat pointer. Do not use unconstrained arrays in foreign subprograms. -Accesses to an unconstrained array is a fat pointer. Other accesses correspond to an address and are passed to a subprogram like other non-composite types. +Accesses to an unconstrained array are fat pointers. Other accesses correspond to an address and are passed to a subprogram like other non-composite types. -Files are represented by a 32 bits word, which corresponds to an index +Files are represented by a 32 bit word, which corresponds to an index in a table. .. _Linking_with_foreign_object_files: @@ -324,7 +324,7 @@ Linking with foreign object files --------------------------------- You may add additional files or options during the link using the -*-Wl,* of `GHDL`, as described in :ref:`Elaboration_command`. +*-Wl,* of `GHDL`, as described in ':ref:`Elaboration:command`'. For example:: ghdl -e -Wl,-lm math_tb @@ -386,7 +386,7 @@ design apex is ``design``. $ ghdl --bind design -Finally, compile, bind your `Ada` program at link it with your `VHDL` +Finally, compile, bind your `Ada` program and link it with your `VHDL` design:: $ gnatmake my_prog -largs `ghdl --list-link design` @@ -396,9 +396,9 @@ Using GRT from Ada ------------------ .. warning:: - This topic is only for advanced users knowing how to use `Ada` - and `GNAT`. This is provided only for reference, I have tested - this once before releasing `GHDL` 0.19 but this is not checked at + This topic is only for advanced users who know how to use `Ada` + and `GNAT`. This is provided only for reference; I have tested + this once before releasing `GHDL` 0.19, but this is not checked at each release. The simulator kernel of `GHDL` named :dfn:`GRT` is written in @@ -434,7 +434,7 @@ tested this step. You are now ready to use it. -For example, here is an example, :file:`test_grt.adb` which displays the top +Here is an example, :file:`test_grt.adb` which displays the top level design name. .. code-block:: Ada |