3.18.2 DS390 Memory Model

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3.18.2 DS390 Memory Model

The only model supported is Flat 24. This generates code for the 24 bit contiguous addressing mode of the Dallas DS80C390 part. In this mode, up to four meg of external RAM or code space can be directly addressed. See the data sheets at www.dalsemi.com for further information on this part.
Note that the compiler does not generate any code to place the processor into 24 bitmode (although tinibios in the ds390 libraries will do that for you). If you don't use tinibios, the boot loader or similar code must ensure that the processor is in 24 bit contiguous addressing mode before calling the SDCC startup code.
Like the --model-large option, variables will by default be placed into the XDATA segment.
Segments may be placed anywhere in the 4 meg address space using the usual --*-loc options. Note that if any segments are located above 64K, the -r flag must be passed to the linker to generate the proper segment relocations, and the Intel HEX output format must be used. The -r flag can be passed to the linker by using the option -Wl-r on the SDCC command line. However, currently the linker can not handle code segments > 64k.

Next: 3.19 Pragmas Up: 3.18 Memory Models Previous: 3.18.1 MCS51 Memory Models Contents Index