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114 lines
4.1 KiB
114 lines
4.1 KiB
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
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<html>
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
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<meta name="GENERATOR" content="Mozilla/4.72 [en] (WinNT; U) [Netscape]">
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<title>The b Command</title>
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</head>
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<body>
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<h1>
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b</h1>
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<!--INDEX "breakpoint number" brkcmd "b command" -->
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<p>The b command sets and displays breakpoints.
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<h2>
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Format</h2>
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<dl>
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<dd> The format for the b command is:</dd>
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<pre><font size="+1">b
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b <i>adr..
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</i>b <i>adr</i> -s <i>str</i></font>
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where:
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</pre>
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<table width="95%">
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<tr bgcolor="#CCCCCC">
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<td ALIGN=LEFT VALIGN=TOP WIDTH="74"><i>adr</i></td>
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<td width="695">specifies an address for the breakpoint. Up to 32 breakpoints
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addresses can be set. </td>
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</tr>
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<tr>
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<td width="74">-s <i>str</i></td>
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<td width="695">executes the command string when the breakpoint is hit. </td>
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</tr>
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</table>
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<p>Invoking the b command with no options causes the <a href="mondef.htm">Monitor</a>
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to print a list of the current breakpoints.
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</dl>
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<h2>
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Functional Description</h2>
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<dl>
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<dd> The b command sets a breakpoint at the specified address or addresses.
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Multiple addresses may be specified. Specified addresses must be word-aligned.</dd>
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<br>
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<p>The <a href="mondef.htm">Monitor</a> automatically assigns a number to each
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breakpoint. <br>
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The <a href="mondef.htm">Monitor</a> allocates the lowest available breakpoint
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number from 0 to 31 to any new breakpoint.
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<p>The <a href="mondef.htm">Monitor</a> reports a new breakpoint's number immediately
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after the breakpoint is set (see the examples at the end of this subsection
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for illustration of this). The assigned numbers can be used in the <a href="c_db.htm">db</a>
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(Delete Breakpoint) command.
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<p><b>The brkcmd Variable</b>
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<p>When a breakpoint is reached, the command list specified in the environment
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variable brkcmd is executed. The default setting for brkcmd is:
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<pre>brkcmd = "l @pc 1"</pre>
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This command "<tt>l @pc 1</tt>", specifies that when the breakpoint occurs,
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the <a href="mondef.htm">Monitor</a> will disassemble one line starting at the
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address of the program counter.
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<p>You can change the breakpoint command variable with the set command. For
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example, you can include additional monitor commands in the brkcmd variable.
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You must separate additional commands on the command line with a semicolon.
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For example, entering the following command lists one line after reaching
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a breakpoint, and then displays all the register values.
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<pre>set brkcmd "l @epc 1;r *"
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</pre>
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By default, breakpoints are cleared when the load command is executed. See the
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section on the load command later in this document for details on how to override
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automatic breakpoint clearing after a download operation.
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<p>Some examples illustrating the use of the b command follow. <br>
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<table width="95%">
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<tr bgcolor="#CCCCCC">
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<td width="231"><tt>PMON> b a002000c </tt></td>
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<td width="538">Set a breakpoint at 0xa002000c. </td>
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</tr>
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<tr>
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<td width="231"><tt>Bpt 1 = a002000c </tt></td>
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</tr>
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<tr bgcolor="#CCCCCC">
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<td width="231"><tt>PMON> b </tt> <br>
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<tt>Bpt 0 = 8002022c</tt> <br>
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<tt>Bpt 1 = a002000c </tt></td>
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<td VALIGN=TOP width="538">Display all breakpoints. </td>
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</tr>
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<tr>
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<td VALIGN=TOP width="231"><tt>PMON> b 80021248 -s "r" </tt></td>
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<td width="538">Set a breakpoint at 0x80021248. Display registers when the
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breakpoint is encountered. </td>
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</tr>
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</table>
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</dl>
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<h2>
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See Also</h2>
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<dl>
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<dd>
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<a href="c_db.htm">db</a> and <a href="c_load.htm">load</a> commands.</dd>
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</dl>
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<hr>
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<p><b>Navigation:</b> <a href="pmon.htm">Document Home</a> | <a href="doctoc.htm">Document
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Contents</a> | <a href="docindex.htm">Document Index</a>
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<p><!--$Id: c_b.htm,v 1.1.1.1 2006/09/14 01:59:06 root Exp $ -->
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</body>
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</html>
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