175 lines
7.3 KiB
HTML
175 lines
7.3 KiB
HTML
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<!DOCTYPE html>
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<html lang="en" data-content_root="../../../">
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<head>
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<meta charset="utf-8" />
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<meta name="viewport" content="width=device-width, initial-scale=1.0" /><meta name="viewport" content="width=device-width, initial-scale=1" />
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<title>Thread Details — Icarus Verilog documentation</title>
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<link rel="stylesheet" type="text/css" href="../../../_static/pygments.css?v=fa44fd50" />
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<link rel="index" title="Index" href="../../../genindex.html" />
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<link rel="search" title="Search" href="../../../search.html" />
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<link rel="next" title="Debug Aids For VVP" href="debug.html" />
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<link rel="prev" title="VPI Within VVP" href="vpi.html" />
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<meta name="viewport" content="width=device-width, initial-scale=0.9, maximum-scale=0.9" />
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</head><body>
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<div class="document">
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<div class="body" role="main">
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<section id="thread-details">
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<h1>Thread Details<a class="headerlink" href="#thread-details" title="Link to this heading">¶</a></h1>
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<p>Thread objects in vvp are created by <cite>.thread</cite> statements in the
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input source file.</p>
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<p>A thread object includes a program counter and private bit
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registers. The program counter is used to step the processor through
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the code space as it executes instructions. The bit registers each
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hold Verilog-style 4-value bits and are for use by the arithmetic
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operators as they operate.</p>
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<p>The program counter normally increments by one instruction after the
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instruction is fetched. If the instruction is a branching instruction,
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then the execution of the instruction sets a new value for the pc.</p>
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<p>Instructions that use the bit registers have as an operand a <bit>
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value. There is usually space in the instruction for 2 <bit>
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operands. Instructions that work on vectors pull the vector values
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from the bit registers starting with the LSB and up.</p>
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<p>The bit addresses 0, 1, 2 and 3 are special constant bits 0, 1, x and
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z, and are used as read-only immediate values. If the instruction
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takes a single bit operand, then the appropriate value is simply read
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out. If the instruction expects a vector, then a vector of the
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expected width is created by replicating the constant value.</p>
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<p>Bits 4, 5, 6 and 7 are read/write bits but are reserved by many
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instructions for special purposes. Comparison operators, for example,
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use these as comparison flag bits.</p>
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<p>The remaining 64K-8 possible <bit> values are read-write bit registers
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that can be accessed singly or as vectors. This obviously implies that
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a bit address is 16 bits.</p>
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<p>Threads also contain 16 numeric registers. These registers can hold a
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real value or a 64bit integer, and can be used in certain cases where
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numeric values are needed. The thread instruction set includes
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%ix/* instructions to manipulate these registers. The instructions
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that use these registers document which register is used, and what the
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numeric value is used for. Registers 0-3 are often given fixed
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meanings to instructions that need an integer value.</p>
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<div class="highlight-none notranslate"><div class="highlight"><pre><span></span>/*
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* Copyright (c) 2001-2024 Stephen Williams (steve@icarus.com)
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*
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* This source code is free software; you can redistribute it
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* and/or modify it in source code form under the terms of the GNU
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* General Public License as published by the Free Software
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* Foundation; either version 2 of the License, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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</pre></div>
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</div>
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</section>
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</div>
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</div>
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</div>
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<div class="sphinxsidebar" role="navigation" aria-label="main navigation">
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<div class="sphinxsidebarwrapper">
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<h1 class="logo"><a href="../../../index.html">Icarus Verilog</a></h1>
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<h3>Navigation</h3>
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<p class="caption" role="heading"><span class="caption-text">Contents:</span></p>
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<ul class="current">
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<li class="toctree-l1"><a class="reference internal" href="../../../usage/index.html">Icarus Verilog Usage</a></li>
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<li class="toctree-l1"><a class="reference internal" href="../../../targets/index.html">The Icarus Verilog Targets</a></li>
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<li class="toctree-l1 current"><a class="reference internal" href="../../index.html">Icarus Verilog Developer Support</a><ul class="current">
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<li class="toctree-l2"><a class="reference internal" href="../../getting_started.html">Getting Started as a Contributor</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../../regression_tests.html">The Regression Test Suite</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../../version_stamps.html">Files With Version Information</a></li>
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<li class="toctree-l2 current"><a class="reference internal" href="../index.html">Developer Guide</a></li>
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<li class="toctree-l2"><a class="reference internal" href="../../glossary.html">Glossary</a></li>
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</ul>
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</li>
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</ul>
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<div class="relations">
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<h3>Related Topics</h3>
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<ul>
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<li><a href="../../../index.html">Documentation overview</a><ul>
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<li><a href="../../index.html">Icarus Verilog Developer Support</a><ul>
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<li><a href="../index.html">Developer Guide</a><ul>
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<li><a href="index.html">VVP - Verilog Virtual Processor</a><ul>
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<li>Previous: <a href="vpi.html" title="previous chapter">VPI Within VVP</a></li>
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<li>Next: <a href="debug.html" title="next chapter">Debug Aids For VVP</a></li>
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</ul></li>
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</ul></li>
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©2024-2025, Stephen Williams.
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<a href="../../../_sources/developer/guide/vvp/vthread.rst.txt"
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