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108 lines
5.5 KiB
HTML
108 lines
5.5 KiB
HTML
<html>
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<title>MARS 4.5 help contents
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</title>
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<body>
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<center>
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<h3>MARS - Mips Assembly and Runtime Simulator</h3>
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<h4>Release 4.5</h4>
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<h4>August 2014</h4>
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<h4>Cool Capability: Plug-in Tools</h4>
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</center>
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Beginning with Release 2.0, MARS is capable of running externally-developed
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software that interacts with an executing MIPS program and MIPS system
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resources.
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The requirements for such a program are:
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<ol>
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<li>It implements the <tt>mars.tools.MarsTool</tt> interface.
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<li>It is part of the <tt>mars.tools</tt> package.
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<li>It compiles cleanly into a ".class" file, stored in the <tt>mars/tools</tt> directory.
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</ol>
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MARS will detect all qualifying tools upon startup and include them in
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its Tools menu.
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When a tool's menu item is selected, an instance of it will be created using its no-argument
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constructor and its <tt>action()</tt> method will be invoked.
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If no qualifying tools are found at MARS startup, the Tools menu will not
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appear.
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<p>To use such a tool, load and assemble a MIPS program of interest then select the desired tool
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from the Tools menu. The tool's window will open and depending on how it is written it will either
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need to be "connected" to the MIPS program by clicking a button or will already be connected. Run
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the MIPS program as you normally would, to initiate tool interaction with the executing program.
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<p>Beginning with Release 3.2, the abstract class <tt>mars.tools.AbstractMarsToolAndApplication</tt>
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is included in the MARS distribution to provide
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a substantial framework for implementing your own MARS Tool. A subclass that extends it by
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implementing at least its two abstract methods can be run not only from the Tools menu but also
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as a free-standing application that uses the MARS assembler and simulator in the background.
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<p>Several Tools developed by subclassing <tt>AbstractMarsToolAndApplication</tt> are included
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with MARS: an Introduction to Tools, a Data Cache Simulator, a Memory Reference Visualizer, and
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a Floating Point tool. The last one is quite useful even when not connected to a MIPS program
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because it displays binary, hexadecimal and decimal representations for a 32 bit floating point
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value; when any of them is modified the other two are updated as well.
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<p>Release 3.5 includes new tools, most notably a keyboard and display simulator that allows you
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to perform memory-mapped I/O (MMIO) using polled and interrupt-driven techniques as described
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in various references. Click its Help button for more details.
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<p>If you wish to develop your own MARS Tool, you will first need to extract the MARS distribution
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from its JAR file if you have not already done so. All MARS tools must
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be stored in the <tt>mars/tools</tt> directory.
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<p>Follow the Tutorial Materials link on the MARS homepage to find a tutorial
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that covers development of MARS Tools.
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<h4>Cool Capability: Extending the syscall set or reassigning syscall numbers</h4>
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Beginning with Release 3.1, system calls (<tt>syscall</tt> instruction) are implemented using
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a technique similar to that for tools. This permits anyone to add a new syscall by defining
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a new class that meets these requirements:
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<ol>
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<li>It implements the <tt>mars.mips.instructions.syscalls.Syscall</tt> interface, or
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extends the <tt>mars.mips.instructions.syscalls.AbstractSyscall</tt> class (which
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provides default implementations of everything except the <tt>simulate()</tt> method).
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<li>It is part of the <tt>mars.mips.instructions.syscalls</tt> package.
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<li>It compiles cleanly into a ".class" file, stored in the
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<tt>mars/mips/instructions/syscalls</tt> directory.
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</ol>
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MARS will detect all qualifying syscall classes upon startup and the runtime simulator
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will invoke them when the <tt>syscall</tt> instruction is simulated and register <tt>$v0</tt>
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contains the corresponding integer service number.
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<p>Syscalls and syscall number assignments in MARs match those of SPIM for syscalls 1 through 17.
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However if you wish to change syscall number assignments, you may do so by editing the
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<tt>Syscall.properties</tt> file included in the release (this requires extraction from the JAR
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file).
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<p>Follow the Tutorial Materials link on the MARS homepage to find a tutorial
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that covers development of system calls.
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<h4>Cool Capability: Extending the instruction set</h4>
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You can add customized pseudo-instructions to the MIPS instruction set by editing
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the <tt>PseudoOps.txt</tt> file included in the MARS distribution. Instruction
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specification formats are explained in the file itself.
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The specification of a pseudo-instruction is one line long. It consists of
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an example of the instruction, constructed using
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available instruction specification symbols, followed by a tab-separated
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list of the basic MIPS instructions it will expand to. Each is an instruction template
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constructed using
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instruction specification symbols combined with special template
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specification symbols. The latter permit substitution at program
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assembly time of operands from the user's program into the expanded
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pseudo-instruction.
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<p><tt>PseudoOps.txt</tt> is read and processed at MARS startup, and error messages will
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be produced if a specification is not correctly formatted. Note that if you wish to
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edit it you first have to extract it from the JAR file.
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<p>Follow the Tutorial Materials link on the MARS homepage to find a tutorial
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that covers modification of the pseudo-instruction set.
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<p>
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<hr>
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<p>
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This document is available for printing on the MARS home page
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<tt><b>http://www.cs.missouristate.edu/MARS/</b></tt>.
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</body>
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</html> |