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Document the UDP implementation.

This commit is contained in:
steve 2001-04-25 04:35:05 +00:00
parent 0ab60cd3c3
commit c997c090a1
2 changed files with 73 additions and 4 deletions
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63
vvp/README.txt
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@ -1,7 +1,7 @@
/*
* Copyright (c) 2001 Stephen Williams (steve@icarus.com)
*
* $Id: README.txt,v 1.16 2001/04/18 04:21:23 steve Exp $
* $Id: README.txt,v 1.17 2001/04/25 04:35:05 steve Exp $
*/
VVP SIMULATION ENGINE
@ -99,6 +99,67 @@ Almost all of the structural aspects of a simulation can be
represented by functors, which perform the very basic task of
combining up to four inputs down to one output.
UDP STATEMENTS:
A UDP statement either defines a User Defined Primitive, or
instantiates a previously defined UDP by creating a UDP functor. A
UDP functor has as many inputs as the UDP definition requires.
UDPs come in sequential and combinatorial flavors. Sequential UDPs
carry an output state and can respond to edges at the inputs. The
output of a combinatorial UDPs is a function of its current inputs
only.
The function of a UDP is defined via a table. The rows of the table
are strings which describe input states or edges, and the new output
state. Combinatorial UDPs require one character for each input, and
one character at the end for the output state. Sequential UDPs need
an additional char for the current state, which is the first char of
the row.
Any input transition or the new state must match at most one row (or
all matches must provide the same output state). If no row matches,
the output becomes 1'bx.
The output state can be specified as "0", "1", or "x". Sequential
UDPs may also have "-": no change.
An input or current output state can be "1", "0", "x", or "?" (don't
care). For Sequential UDPs, at most one input state specification may
be replaced by an edge specification. Valid edges are:
"*": (??) "_": (?0) "+": (?1) "%": (?x)
"r": (01) "R": (x1) "f": (10) "F": (x0)
"p": (0?) "n": (1?) "P": (0x) "N": (1x)
A combinatorial UDP is defined like this:
<type> .udp/comb "<name>", <number>, "<row0>", "<row1>", ... ;
<type> is a label that identifies the UDP. <number> is the number of
inputs. "<name>" is there for public identification. Sequential UDPs
need an additional initialization value:
<type> .udp/sequ "<name>", <number>, <init>, "<row0>", "<row1>", ... ;
<init> is the initial value for all instances of the UDP. We do not
provide initial values for individual instances. <init> must be a
number 0, 1, or 2 (for 1'bx).
A UDP functor instance is created so:
<label> .udp <type>, <symbol_list> ;
Where <label> identifies the functor, <type> is the label of a UDP
defined earlier, and <symbol_list> is a list of symbols, one for each
input of the UDP.
ATTN: The "<name>" attribute of the UDP is pretty useless, and may go
away in future versions. It may be useful for diagnostic messages,
though.
VARIABLE STATEMENTS:
A variable is a bit vector that can be written by behavioral code (so

14
vvp/compile.h
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@ -19,7 +19,7 @@
* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
*/
#if !defined(WINNT)
#ident "$Id: compile.h,v 1.17 2001/04/24 02:23:59 steve Exp $"
#ident "$Id: compile.h,v 1.18 2001/04/25 04:35:05 steve Exp $"
#endif
# include <stdio.h>
@ -66,8 +66,13 @@ extern void compile_vpi_symbol(const char*label, vpiHandle obj);
extern vpiHandle compile_vpi_lookup(const char*label);
/*
* The first function creates a UDP, the second function adds table
entries, and the third one instantiates a UDP functor.
* The `compile_udp_def' function creates a UDP. The `table' is a
* NULL terminated array of char*, as assembled by `compile_udp_table'.
* `compile_udp_table' is called with `table'==NULL to create a new
* table, or with an existing table to append to.
*
* `compile_udp_functor' creates a mode-3 functor refering to the
* labeled UDP.
*/
extern void compile_udp_def(int sequ, char*label, char *name,
@ -155,6 +160,9 @@ extern void compile_dump(FILE*fd);
/*
* $Log: compile.h,v $
* Revision 1.18 2001/04/25 04:35:05 steve
* Document the UDP implementation.
*
* Revision 1.17 2001/04/24 02:23:59 steve
* Support for UDP devices in VVP (Stephen Boettcher)
*