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<H2><A NAME="SECTION000417000000000000000">
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3.17 DS390 Memory Models</A>
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</H2>
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<P>
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The only model supported is Flat 24. This generates code for the 24
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bit contiguous addressing mode of the Dallas DS80C390 part. In this
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mode, up to four meg of external RAM or code space can be directly
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addressed. See the data sheets at www.dalsemi.com for further information
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on this part.
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<BR>
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<BR>
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In older versions of the compiler, this option was used with the MCS51
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code generator (<I>-mmcs51</I>). Now, however, the '390 has it's own
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code generator, selected by the <I>-mds390</I> switch.
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<BR>
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<BR>
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Note that the compiler does not generate any code to place the processor
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into 24 bitmode (although <I>tinibios</I> in the ds390 libraries will
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do that for you). If you don't use <I>tinibios</I>, the boot loader
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or similar code must ensure that the processor is in 24 bit contiguous
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addressing mode before calling the SDCC startup code.
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<BR>
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<BR>
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Like the <I>-model-large</I> option, variables will by default be
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placed into the XDATA segment.
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<BR>
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<BR>
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Segments may be placed anywhere in the 4 meg address space using the
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usual -*-loc options. Note that if any segments are located above
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64K, the -r flag must be passed to the linker to generate the proper
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segment relocations, and the Intel HEX output format must be used.
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The -r flag can be passed to the linker by using the option <I>-Wl-r</I>
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on the sdcc command line. However, currently the linker can not handle
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code segments > 64k.
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HREF="node19.html">3. Using SDCC</A>
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HREF="node35.html">3.16 MCS51 Memory Models</A>
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<ADDRESS>
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<I>Johan Knol</I>
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<BR><I>2001-07-13</I>
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