mirror of https://github.com/cc65/cc65.git
500 lines
16 KiB
Plaintext
500 lines
16 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Commodore 64-specific information for cc65
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<author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz"><newline>
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<url url="mailto:greg.king5@verizon.net" name="Greg King">
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<abstract>
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An overview over the C64 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 C64 runtime system as it comes with the
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cc65 C compiler. It describes the memory layout, C64-specific header files,
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available drivers, and any pitfalls specific to that platform.
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Please note that C64-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>Binary format<p>
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The standard binary output format generated by the linker for the C64 target
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is a machine language program with a one line BASIC stub, which calls the
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machine language part via SYS. This means that a program can be loaded as
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BASIC program and started with RUN. It is of course possible to change this
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behaviour by using a modified startup file and linker config.
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<sect>Memory layout<p>
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cc65 generated programs with the default setup run with the I/O area and the
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kernal ROM enabled (memory under the kernal may be used for graphics or as
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extended memory - see the sections about graphics and extended memory
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drivers). The BASIC ROM is disabled, which gives a usable memory range of
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$0800 - $CFFF. This means that kernal entry points may be called
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directly, but using the BASIC ROM is not possible without additional code.
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Special locations:
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<descrip>
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<tag/Text screen/
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The text screen is located at $400 (as in the standard setup).
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<tag/Stack/
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The C runtime stack is located at $CFFF and growing downwards.
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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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</descrip><p>
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<sect>Linker configurations<p>
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The ld65 linker comes with a default config file for the Commodore 64,
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which is used via <tt/-t c64/. The
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c64 package comes with additional secondary linker config files, which are
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used via <tt/-t c64 -C <configfile>/.
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<sect1>default config file (<tt/c64.cfg/)<p>
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The default configuration is tailored to C programs. It supplies the load
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address and a small BASIC stub that starts the compiled program using a SYS
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command.
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<sect1><tt/c64-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. The default start address is $801. It can be changed with the
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linker command line option <tt/--start-addr/. All standard segments with the
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exception of <tt/zeropage/ are written to the output file and a two byte load
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address is prepended.
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To use this config file, assemble with <tt/-t c64/ and link with <tt/-C
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c64-asm.cfg/. The former will make sure that correct character translation is
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in effect, 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 line for <tt/cl65/:
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<tscreen><verb>
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cl65 -o file.prg -t c64 -C c64-asm.cfg source.s
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</verb></tscreen>
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To generate code that loads to $C000:
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<tscreen><verb>
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cl65 -o file.prg --start-addr $C000 -t c64 -C c64-asm.cfg source.s
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</verb></tscreen>
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It is also possible to add a small BASIC header to the program, that uses SYS
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to jump to the program entry point (which is the start of the code segment).
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The advantage is that the program can be started using RUN.
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To generate a program with a BASIC SYS header, use
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<tscreen><verb>
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cl65 -o file.prg -u __EXEHDR__ -t c64 -C c64-asm.cfg source.s
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</verb></tscreen>
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Please note that in this case a changed start address doesn't make sense,
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since the program must be loaded to the BASIC start address.
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<sect>Extras<p>
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<sect1>80 Columns conio driver<p>
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The C64 package comes with an alternative software driven 80 columns
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module <tt/c64-soft80.o/ which uses the memory under I/O between $D000
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and $FF3F.
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In memory constrained situations the memory from $400 to $7FF
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can be made available to a program by calling <tt/_heapadd ((void *) 0x0400, 0x0400);/
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at the beginning of <tt/main()/. Doing so is beneficial even if the program
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doesn't use the heap explicitly because loading a driver uses the heap implicitly.
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Using <tt/c64-soft80.o/ is as simple as placing it on the linker command
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line like this:
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<tscreen><verb>
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cl65 -t c64 myprog.c c64-soft80.o
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</verb></tscreen>
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Note that the soft80 conio driver is incompatible with the
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<tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
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<tt/c64-hi.tgi (c64_hi_tgi)/ graphics driver.
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<sect2>80 Columns conio driver (monochrome)<p>
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In an (even more) memory constrained situation, a size optimized version of the
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software driven 80 columns module may be used, which only supports one common
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text color for the whole screen.
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<tscreen><verb>
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cl65 -t c64 myprog.c c64-soft80mono.o
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</verb></tscreen>
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<sect>Platform-specific header files<p>
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Programs containing C64-specific code may use the <tt/c64.h/ or <tt/cbm.h/
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header files. Using the later may be an option when writing code for more than
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one CBM platform, since it includes <tt/c64.h/ and declares several functions
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common to all CBM platforms.
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<sect1>C64-specific functions<p>
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The functions listed below are special for the C64. See the <url
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url="funcref.html" name="function reference"> for declaration and usage.
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<itemize>
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<item>get_ostype
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</itemize>
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<sect1>C64-specific accelerator functions<p>
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The functions listed below are accelerator functions for the C64. See the <url
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url="funcref.html" name="function reference"> for declaration and usage.
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<itemize>
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<item>detect_c128
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<item>detect_c64dtv
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<item>detect_c65
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<item>detect_chameleon
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<item>detect_scpu
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<item>detect_turbomaster
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<item>get_c128_speed
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<item>get_c64dtv_speed
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<item>get_c65_speed
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<item>get_chameleon_speed
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<item>get_scpu_speed
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<item>get_turbomaster_speed
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<item>set_c128_speed
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<item>set_c64dtv_speed
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<item>set_c65_speed
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<item>set_chameleon_speed
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<item>set_scpu_speed
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<item>set_turbomaster_speed
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</itemize>
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<sect1>CBM-specific functions<p>
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Some functions are available for all (or at least most) of the Commodore
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machines. See the <url url="funcref.html" name="function reference"> for
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declaration and usage.
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<itemize>
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<item>cbm_close
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<item>cbm_closedir
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<item>cbm_k_setlfs
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<item>cbm_k_setnam
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<item>cbm_k_load
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<item>cbm_k_save
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<item>cbm_k_open
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<item>cbm_k_close
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<item>cbm_k_readst
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<item>cbm_k_chkin
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<item>cbm_k_ckout
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<item>cbm_k_basin
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<item>cbm_k_bsout
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<item>cbm_k_clrch
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<item>cbm_k_tksa
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<item>cbm_k_second
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<item>cbm_load
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<item>cbm_open
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<item>cbm_opendir
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<item>cbm_read
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<item>cbm_readdir
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<item>cbm_save
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<item>cbm_write
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<item>get_tv
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<item>waitvsync
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</itemize>
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<sect1>Hardware access<p>
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The following pseudo variables declared in the <tt/c64.h/ header file do allow
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access to hardware located in the address space. Some variables are
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structures, accessing the struct fields will access the chip registers.
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<descrip>
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<tag><tt/VIC/</tag>
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The <tt/VIC/ structure allows access to the VIC II (the graphics
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controller). See the <tt/_vic2.h/ header file located in the include
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directory for the declaration of the structure.
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<tag><tt/SID/</tag>
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The <tt/SID/ structure allows access to the SID (the sound interface
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device). See the <tt/_sid.h/ header file located in the include directory
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for the declaration of the structure.
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<tag><tt/CIA1, CIA2/</tag>
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Access to the two CIA (complex interface adapter) chips is available via
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the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
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is explained in <tt/_6526.h/.
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<tag><tt/COLOR_RAM/</tag>
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A character array that mirrors the color RAM of the C64 at $D800.
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</descrip><p>
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<sect>Loadable drivers<p>
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The names in the parentheses denote the symbols to be used for static linking of the drivers.
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<label id="graphics-drivers">
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<sect1>Graphics drivers<p>
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<em>Note:</em> All available graphics drivers for the TGI interface will use
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the space below the I/O area and Kernal ROM; so, you can have hires graphics in
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the standard setup without any memory loss or need for a changed configuration.
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You can use a mouse driver at the same time that you use a TGI driver. But, if
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you want to see the default mouse pointer on the graphics screen, then you
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explicitly must link a special object file into your program. It will put the
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arrow into the "high RAM" area where the bitmaps are put. Its name is
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"<tt/c64-tgimousedata.o/". Example:
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<tscreen><verb>
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cl65 -t c64 -o program-file main-code.c subroutines.s c64-tgimousedata.o
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</verb></tscreen>
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<descrip>
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<tag><tt/c64-hi.tgi (c64_hi_tgi)/</tag>
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This driver features a resolution of 320*200 with two colors and an
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adjustable palette (that means that the two colors can be chosen out of a
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palette of the 16 C64 colors).
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</descrip><p>
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Note that the graphics drivers are incompatible with the
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<tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
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<tt/c64-soft80.o/ software 80-columns conio driver.
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<sect1>Extended memory drivers<p>
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<descrip>
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<tag><tt/c64-65816.emd (c64_65816_emd)/</tag>
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Extended memory driver for 65816 (eg SCPU) based extra RAM.
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Written and contributed by Marco van den Heuvel.
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<tag><tt/c64-c256k.emd (c64_c256k_emd)/</tag>
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A driver for the C64 256K memory expansion. This driver offers 768 pages of
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256 bytes each. Written and contributed by Marco van den Heuvel.
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<tag><tt/c64-dqbb.emd (c64_dqbb_emd)/</tag>
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A driver for the Double Quick Brown Box cartridge. This driver offers
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64 pages of 256 bytes each. Written and contributed by Marco van den Heuvel.
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<tag><tt/c64-georam.emd (c64_georam_emd)/</tag>
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A driver for the Berkeley Softworks GeoRam cartridge. The driver will
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determine the available RAM from the connected cartridge. It supports 64KB
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up to 2048KB of RAM.
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<tag><tt/c64-isepic.emd (c64_isepic_emd)/</tag>
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A driver for the ISEPIC cartridge. This driver offers just 8 pages of 256
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bytes each. Written and contributed by Marco van den Heuvel.
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<tag><tt/c64-kerberos.emd (c64_kerberos_emd)/</tag>
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A driver for the Kerberos MIDI Cartridge. The cartridge has 512
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pages of 256 bytes for a total of 128KB.
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<tag><tt/c64-ram.emd (c64_ram_emd)/</tag>
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A driver for the hidden RAM below the I/O area and kernal ROM. Supports 47
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256 byte pages. Please note that this driver is incompatible with any of the
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graphics drivers, or the soft80 conio driver!
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<tag><tt/c64-ramcart.emd (c64_ramcart_emd)/</tag>
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A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
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Will test the hardware for the available RAM.
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<tag><tt/c64-reu.emd (c64_reu_emd)/</tag>
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A driver for the CBM REUs. The driver will test the connected REU to find
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out how much RAM is present.
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<tag><tt/c64-vdc.emd (c64_vdc_emd)/</tag>
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A driver for the VDC memory of the C128. Written and contributed by Maciej
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Witkowiak. Can be used if the program is running in C64 mode of the C128.
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Autodetects the amount of memory available (16 or 64K) and offers 64 or 256
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pages of 256 bytes each.
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<tag><tt/dtv-himem.emd (dtv_himem_emd)/</tag>
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A driver for the C64 D2TV (the second or PAL version). This driver offers
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indeed 7680 pages of 256 bytes each.
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</descrip><p>
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<sect1>Joystick drivers<p>
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The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/c64-stdjoy.joy (c64_stdjoy_joy)/.
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<descrip>
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<tag><tt/c64-hitjoy.joy (c64_hitjoy_joy)/</tag>
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Driver for the Digital Excess & Hitmen adapter contributed by Groepaz.
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See <url url="http://www.digitalexcess.de/downloads/productions.php"> on
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instructions how to build one. Up to four joysticks are supported.
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<tag><tt/c64-ptvjoy.joy (c64_ptvjoy_joy)/</tag>
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Driver for the Protovision 4-player adapter contributed by Groepaz. See
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<url url="http://www.protovision-online.de/hardw/4_player.php?language=en"
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name="Protovision shop"> for prices and building instructions. Up to four
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joysticks are supported.
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<tag><tt/c64-stdjoy.joy (c64_stdjoy_joy)/</tag>
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Supports up to two standard joysticks connected to the joysticks port of
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the C64.
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<tag><tt/c64-numpad.joy (c64_numpad_joy)/</tag>
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Supports one joystick emulated by the numberpad of the C128 in C64 mode,
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the firebutton is labeled &dquot;5&dquot; and ENTER.
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</descrip><p>
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<sect1>Mouse drivers<p>
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You can use these drivers in text-mode or graphics-mode (TGI) programs. See
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the description of <ref id="graphics-drivers" name="the graphics drivers">.
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The default drivers, <tt/mouse_stddrv (mouse_static_stddrv)/, point to <tt/c64-1351.mou (c64_1351_mou)/.
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<descrip>
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<tag><tt/c64-1351.mou (c64_1351_mou)/</tag>
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Supports a standard mouse connected to port #0 of the C64.
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<tag><tt/c64-inkwell.mou (c64_inkwell_mou)/</tag>
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Supports the Inkwell Systems lightpens, connected to port #0 of the C64.
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It can read both the one-button 170-C and the two-button 184-C pens. (It can
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read other lightpens and light-guns that send their button signal to the
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joystick left-button pin or the paddle Y [up/down] pin.)
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<tag><tt/c64-joy.mou (c64_joy_mou)/</tag>
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Supports a mouse emulated by a standard joystick, e.g. 1350 mouse, in port
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#1 of the C64.
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<tag><tt/c64-pot.mou (c64_pot_mou)/</tag>
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Supports a potentiometer device, e.g. Koala Pad, connected to port #1 of
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the C64.
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</descrip><p>
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<sect1>RS232 device drivers<p>
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<descrip>
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<tag><tt/c64-swlink.ser (c64_swlink_ser)/</tag>
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Driver for the SwiftLink cartridge. Supports up to 38400 baud, requires hardware
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flow control (RTS/CTS) and does interrupt driven receives. Note that, because of
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the peculiarities of the 6551 chip, together with the use of the NMI, transmits
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are not interrupt driven; and, the transceiver blocks if the receiver asserts
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flow control because of a full buffer.
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</descrip><p>
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<sect>Limitations<p>
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<sect1>Realtime clock<p>
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The realtime clock functions use the CIA1 TOD clock. As that clock only stores
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the time but not the date, the date set by <tt/clock_settime()/ is simply stored
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inside the C library for retrieval in the same program via <tt/clock_gettime()/.
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<sect>Other hints<p>
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<sect1>Escape code<p>
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For an Esc, press CTRL and the <tt/[/ key.
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<sect1>Passing arguments to the program<p>
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Command-line arguments can be passed to <tt/main()/. Since this is not
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supported directly by BASIC, the following syntax was chosen:
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<tscreen><verb>
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RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
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</verb></tscreen>
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<enum>
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<item>Arguments are separated by spaces.
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<item>Arguments may be quoted.
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<item>Leading and trailing spaces around an argument are ignored. Spaces within
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a quoted argument are allowed.
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<item>The first argument passed to <tt/main()/ is the program name.
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<item>A maximum number of 10 arguments (including the program name) are
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supported.
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</enum>
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<sect1>Program return code<p>
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The program return code (low byte) is passed back to BASIC by use of the
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<tt/ST/ variable.
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<sect1>Interrupts<p>
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The runtime for the C64 uses routines marked as <tt/.INTERRUPTOR/ for
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interrupt handlers. Such routines must be written as simple machine language
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subroutines and will be called automatically by the interrupt handler code
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when they are linked into a program. See the discussion of the <tt/.CONDES/
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feature in the <url url="ca65.html" name="assembler manual">.
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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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