pmapp.htm

mips架构的bootloader,99左右的版本 但源代码现在没人更新了

	<title>PMON Application</title>
	<h1 align=center>PMON Application</h1>

<!--INDEX "PMON Application" -->

A PMON application (also known as a client), is a program that has
been compiled using the <a href="tools/pmcc.htm">pmcc</a> command and then
downloaded to the target board.<p>

<h2>Client Memory Map</h2>
<!--INDEX "Client Memory Map" -->
<dl><dd>


When the program to be downloaded (client) is linked, the .text, .data,
and .bss sections are all placed one behind the other starting at
0x80020000 (except ATMizer-I).  The heap grows upward from the end of
the .bss section, and the stack grows down from the top of memory. This
stack area is only used by the client. PMON uses a stack that is
located inside its .bss section. Heap overflow is indicated when the
heap pointer crosses the stack pointer.


<pre>
	HIGH MEMORY       +---------------+
			  |               |
			  |   stack  |    |
			  |          v    |
			  |               |
			  +---------------+
			  |		  |
			  |          ^    |
			  |   heap   |    |
			  |		  |
			  +---------------+
			  |      bss      |
			  +---------------+
			  |      data     |
			  +---------------+
	LOW MEMORY	  |      text     |
			  +---------------+
</pre>

</dl>
<h2>PMON I/O operations</h2>
<!--INDEX "PMON I/O operations" -->
<dl><dd>

Downloaded client programs perform all their I/O via PMON (unless they
access the DUART directly). Therefore if you write a program containing
calls to printf. These references will be resolved by a stub of code
in the module lib/crt1.s. This stub uses a vector table, that is 
located at 0x200 bytes from the start of the PMON PROM, to transfer
control to <a href="printf.htm">PMON's printf function</a>.<p>


<pre>
	========> hello.c <========
	main()
	{
	printf("Hello world!\n");
	}

	========> part of crt1.s <========
		.globl printf
		.ent printf
	printf:
		li	t0,TBLBASE+20
		lw	t0,(t0)
		j	t0
		.end printf
</pre>

Where <samp>TBLBASE</samp> is 0xa0c00200 for the ATMizer, and 0xbfc00200 for
all other processors.<p>

The file crt1.s allows a client program to access a number of target-dependent
services provided by the PROM Monitor. The linkage mechanism for all
these services is the <a href="vecttbl.htm">vector table</a>. 

</dl>
</dl><p><hr>
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