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234 lines
7.8 KiB
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234 lines
7.8 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Ohio Scientific-specific information for cc65
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<author>
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<url url="mailto:stephan.muehlstrasser@web.de" name="Stephan Mühlstrasser">,<newline>
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<url url="mailto:greg.king5@verizon.net" name="Greg King">
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<date>2015-03-17
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<abstract>
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An overview over the Ohio Scientific runtime system as it is implemented for the cc65 C
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compiler.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<sect>Overview<p>
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This file contains an overview of the Ohio Scientific runtime system as it comes with the
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cc65 C compiler. It describes the memory layout, Ohio Scientific-specific header files,
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and any pitfalls specific to that platform.
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Please note that Ohio Scientific-specific functions are just mentioned here, they are
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described in detail in the separate <url url="funcref.html" name="function
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reference">. Even functions marked as "platform dependent" may be available on
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more than one platform. Please see the function reference for more
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information.
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<sect>Targets<p>
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Currently the target "osic1p" is implemented. This works for the Ohio Scientific
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Challenger 1P machine and for the Briel Superboard /// replica.
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<sect>Program file formats<p>
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<descrip>
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<tag/Binary, then text/
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The standard binary output format generated by the linker for the osic1p
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target is a pure machine language program.
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For uploading into a real machine over its serial port or into an emulator,
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that program must be converted into a text file that can be understood by
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the 65V PROM monitor. For that purpose, the <bf/srec_cat/ program from <url
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url="http://srecord.sourceforge.net/" name="the SRecord tool collection">
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can be used.
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Care must be taken that the <tt/-offset/ and <tt/-execution-start-address/
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options for the <bf/srec_cat/ program correspond to the start address
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of the executable.
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Example for converting an executable "hello" file that was built for the
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default start address $0200 to an uploadable file "hello.c1p":
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<tscreen><verb>
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srec_cat hello -bin -of 0x200 -o hello.c1p -os -esa=0x200
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</verb></tscreen>
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<tag/Hybrid/
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The linker can create an alternate format that contains two parts:
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<enum>
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<item>A text header that is understood by the 65V PROM monitor.
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It is a boot loader that reads the second part.
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<item>The default binary code that is described above.
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</enum>
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You can make the alternate format by adding the option <tt/-u __BOOT__/ to
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<tt/cl65/'s or <tt/ld65/'s command lines.
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This format doesn't need to be converted. It is smaller than the text-only
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format. But, it cannot be loaded by <url
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url="http://www.pcjs.org/docs/c1pjs/" name="C1Pjs">; you must use the
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SRecord-produced text-only format with that emulator. (However, if you know
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that you never will use C1Pjs, then you can edit the
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<tt>cfg/osic1p*.cfg</tt> files; uncomment the lines that import <tt/__BOOT__/.
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Then, you won't need to use <tt/-u __BOOT__/ on your command lines.)
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</descrip>
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<sect>Memory layout<p>
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By default programs compiled for the osic1p target are configured for 32 kB RAM.
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The RAM size can be configured via the symbol <tt/__HIMEM__/.
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Special locations:
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<descrip>
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<tag/Program start address/
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The default start address is $0200. The start address is configurable
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via the linker option <tt/--start-addr/.
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<tag/Stack/
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The C runtime stack is located at the top of RAM and growing downwards.
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The size is configurable via the symbol <tt/__STACKSIZE__/. The default
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stack size is $0400.
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<tag/Heap/
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The C heap is located at the end of the program and grows towards the C
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runtime stack.
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<tag/Video RAM/
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The 1 kB video RAM is located at $D000. On the monitor, only a subset
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of the available video RAM is visible. The address of the upper left corner
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of the visible area is $D085 and corresponds to conio cursor
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position (0, 0).
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</descrip><p>
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Example for building a program with start address $0300, stack size
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$0200 and RAM size $2000:
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<tscreen><verb>
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cl65 --start-addr 0x300 -Wl -D,__HIMEM__=$2000,-D,__STACKSIZE__=$0200 -t osic1p hello.c
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</verb></tscreen>
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<sect>Linker configurations<p>
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The ld65 linker comes with a default config file "osic1p.cfg" for the Ohio Scientific
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Challenger 1P, which is implicitly used via <tt/-t osic1p/. The
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osic1p package comes with additional secondary linker config files, which are
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used via <tt/-t osic1p -C <configfile>/.
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<sect1>Default config file (<tt/osic1p.cfg/)<p>
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The default configuration is tailored to C programs.
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<sect1><tt/osic1p-asm.cfg/<p>
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This configuration is made for assembler programmers who don't need a special
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setup.
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To use this config file, assemble with <tt/-t osic1p/ and link with
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<tt/-C osic1p-asm.cfg/. The former will make sure that correct runtime library
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is used, while the latter supplies the actual config. When using <tt/cl65/,
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use both command line options.
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Sample command lines for <tt/cl65/:
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<tscreen><verb>
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cl65 -t osic1p -C osic1p-asm.cfg -o program source.s
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cl65 -t osic1p -C osic1p-asm.cfg -u __BOOT__ -o program.lod source.s
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</verb></tscreen>
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<sect>Platform-specific header files<p>
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Programs containing Ohio Scientific-specific code may use the <tt/osic1p.h/
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header file.
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<sect1>Ohio Scientific-specific functions<p>
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There are currently no special Ohio Scientific functions.
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<sect1>Hardware access<p>
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There is no specific support for direct hardware access.
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<sect>Loadable drivers<p>
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There are no loadable drivers available.
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<sect>Support for different screen layouts<p>
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By default the conio library uses a 24 columns by 24 lines screen layout
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for the Challenger 1P, like under BASIC. In addition to that there is support
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for other screen layouts with extra modules.
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There is a module <tt/screen-c1p-24x24.o/ in the OSI-specific
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cc65 runtime library that contains all conio functions that depend
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on the screen layout. No further configuration is needed for using the
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default screen layout of the Challenger 1P.
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For other screen layouts additional versions of the screen module are
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available. The linker finds these modules without further configuration
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if they are specified on the compiler or linker command line. The
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extra module then overrides the default module.
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Sample <tt/cl65/ command line to override the default screen
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module with the module <tt/osic1p-screen-s3-32x28.o/:
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<tscreen><verb>
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cl65 -o hello -t osic1p osic1p-screen-s3-32x28.o hello.c
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</verb></tscreen>
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Currently the following extra screen configuration modules are implemented:
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<itemize>
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<item><tt>osic1p-screen-s3-32x28.o</tt>: 32 columns by 28 lines mode
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for Briel Superboard ///</item>
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</itemize>
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<sect>Limitations<p>
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<sect1>stdio implementation<p>
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There is no support for stdio at the moment.
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<sect>Other hints<p>
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<sect1>Passing arguments to the program<p>
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There is currently no support for passing arguments to a program.
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<sect1>Program return code<p>
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The program return code currently has no effect. When the main() function
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finishes, the boot prompt is shown again.
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<sect>License<p>
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This software is provided 'as-is', without any expressed or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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<enum>
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<item> The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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<item> Altered source versions must be plainly marked as such, and must not
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be misrepresented as being the original software.
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<item> This notice may not be removed or altered from any source
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distribution.
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</enum>
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</article>
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