--- /dev/null
+<!doctype linuxdoc system>
+
+<article>
+
+<title>Commodore 610 specific information for cc65
+<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
+<date>2003-12-16
+
+<abstract>
+An overview over the Commodore 610 runtime system as it is implemented for the
+cc65 C compiler.
+</abstract>
+
+<!-- Table of contents -->
+<toc>
+
+<!-- Begin the document -->
+
+<sect>Overview<p>
+
+This file contains an overview of the CBM 610 runtime system as it comes with
+the cc65 C compiler. It describes the memory layout, CBM 610 specific header
+files, available drivers, and any pitfalls specific to that platform.
+
+Please note that CBM 610 specific functions are just mentioned here, they are
+described in detail in the separate <htmlurl url="funcref.html" name="function
+reference">. Even functions marked as "platform dependent" may be available on
+more than one platform. Please see the function reference for more
+information.
+
+In addition to the Commodore 610 (named B40 in the U.S.), several other
+machines are supported by this cc65 target, since they have identical
+hardware: The Commodore 620 and 630 (more memory, additional coprocessor
+card), and the Commodore 710, 720 and 730 (same hardware in another case with
+a builtin monitor).
+
+
+
+<sect>Binary format<p>
+
+The standard binary output format generated by the linker for the CBM610
+target is a machine language program with a short BASIC stub. This means that
+a program can be loaded as BASIC program and started with RUN. It is of course
+possible to change this behaviour by using a modified startup file and linker
+config.
+
+
+<sect>Memory layout<p>
+
+cc65 generated programs for the Commodore 610 run in bank 1, the memory bank
+reserved for BASIC programs. Since there are no ROMs in this memory bank, the
+program has almost full 64K for its own. A disadvantage is that kernal
+subroutines cannot be called (at least not in a fast and effective manner), so
+the runtime has replace kernal functionality.
+
+The default memory configuration for the CBM 610 allocates all memory between
+$0002 and $FFF0 in bank 1 for the compiled program. Some space
+in low memory is lost, because a separate hardware stack is set up in page 1,
+and the kernal replacement functions need some more memory locations. A few
+more bytes are lost in high memory, because the runtime sets up a CBM
+compatible jump table at $FF81. The main startup code is located at
+$0400, so about 63K of the complete bank are actually usable for
+applications.
+
+<bf>Note:</bf> The zero page from $02 to $5F is free to use for
+applications!
+
+Special locations:
+
+<descrip>
+ <tag/Stack/
+ The C runtime stack is located at $FF81 and growing downwards.
+
+ <tag/Heap/
+ The C heap is located at the end of the program and grows towards the C
+ runtime stack.
+</descrip><p>
+
+
+
+<sect>Platform specific header files<p>
+
+Programs containing CBM 610 specific code may use the <tt/cbm610.h/ or
+<tt/cbm.h/ header files. Using the later may be an option when writing code
+for more than one CBM platform, since it includes <tt/cbm610.h/ and declares
+several functions common to all CBM platforms.
+
+Please note that because of <ref id="limitations" name="current limitations">
+of the runtime library for the platform, several standard C and CBM functions
+are not available.
+
+
+<sect1>CBM 610 specific functions<p>
+
+The functions listed below are special for the CBM 610. See the <htmlurl
+url="funcref.html" name="function reference"> for declaration and usage.
+
+<itemize>
+<item>peekbsys
+<item>peewsys
+<item>pokebsys
+<item>pokewsys
+</itemize>
+
+
+<sect1>CBM specific functions<p>
+
+Some functions are available for all (or at least most) of the Commodore
+machines. See the <htmlurl url="funcref.html" name="function reference"> for
+declaration and usage.
+
+
+<sect1>Hardware access<p>
+
+The following pseudo variables declared in the <tt/cbm610.h/ header file do
+allow access to hardware located in the address space. Some variables are
+structures, accessing the struct fields will access the chip registers.
+
+<bf>Note:</bf> All I/O chips are located in the system bank (bank 15) and can
+therefore not be accessed like on other platforms. Please use one of the
+<tt/peekbsys/, <tt/peewsys/, <tt/pokebsys/ and <tt/pokewsys/ functions to
+access the I/O chips. Direct reads and writes to the structures named below
+will <em>not</em> work!
+
+<descrip>
+
+ <tag><tt/CRTC/</tag>
+ The <tt/CRTC/ structure allows access to the CRTC (the video controller).
+ See the <tt/_6545.h/ header file located in the include directory for the
+ declaration of the structure.
+
+ <tag><tt/SID/</tag> The <tt/SID/ structure allows access to the SID (the
+ sound interface device). See the <tt/_sid.h/ header file located in the
+ include directory for the declaration of the structure.
+
+ <tag><tt/ACIA/</tag>
+ Access to the ACIA (the RS232 chip) is available via the <tt/ACIA/ variable.
+ See the <tt/_6551.h/ header file located in the include directory for the
+ declaration of the structure.
+
+ <tag><tt/CIA/</tag>
+ Access to the CIA chip is available via the <tt/CIA/ variable. See the
+ <tt/_6526.h/ header file located in the include directory for the
+ declaration of the structure.
+
+ <tag><tt/TPI1, TPI2/</tag>
+ The two 6525 triport chips may be accessed by using this variable. See the
+ <tt/_6525.h/ header file located in the include directory for the
+ declaration of the structure.
+
+</descrip><p>
+
+
+
+<sect>Loadable drivers<p>
+
+<bf>Note:</bf> Since the CBM 610 doesn't have working disk I/O (see <ref
+id="limitations" name="section "Limitations"">), the available
+drivers cannot be loaded at runtime (so the term "loadable drivers" is
+somewhat misleading). Instead, the drivers have to be converted using the
+<htmlurl url="co65.html" name="co65 utility"> and statically linked. While
+this may seem overhead, it has two advantages:
+
+<enum>
+<item>The interface is identical to the one used for other platforms
+ and to the one for the CBM 610 once it has disk I/O.
+<item>Once disk I/O is available, existing code can be changed to load drivers
+ at runtime with almost no effort.
+</enum>
+
+
+<sect1>Graphics drivers<p>
+
+No graphics drivers are currently available for the Commodore 610 (and since
+the machine has no graphics capabilities, chances for a graphics driver aren't
+really good:-).
+
+
+<sect1>Extended memory drivers<p>
+
+<descrip>
+ <tag><tt/cbm610-ram.emd/</tag>
+ A driver for the RAM in bank 2. Supports up to 255 pages with 256 bytes
+ each. Untested!
+</descrip><p>
+
+
+<sect1>Joystick drivers<p>
+
+The Commodore 610 is a business machine and doesn't have joystick ports. There
+are no drivers for the non existing ports available.
+
+
+
+<sect1>Mouse drivers<p>
+
+Currently no drivers available (in fact, the API for loadable mouse drivers
+does not exist).
+
+
+<sect1>RS232 device drivers<p>
+
+Currently no RS232 drivers exist for the Commodore 610.
+
+
+
+<sect>Limitations<label id="limitations"><p>
+
+
+<sect1>Disk I/O<p>
+
+The existing library for the CBM 610 doesn't implement C file I/O. Please note
+that this includes <tt/printf/! You may use the conio functions for screen I/O.
+
+To be more concrete, this limitation means that you cannot use any of the
+following functions (and a few others):
+
+<itemize>
+<item>fclose
+<item>fgets
+<item>fopen
+<item>fread
+<item>fprintf
+<item>fputc
+<item>fscanf
+<item>fwrite
+<item>gets
+<item>printf
+<item>...
+</itemize>
+
+
+<sect1>Kernal and hardware access<p>
+
+Since the program runs in bank 1, and the kernal and all I/O chips are located
+in bank 15, calling ROM routines or accessing hardware needs special code.
+
+
+
+<sect>Other hints<p>
+
+<sect1>Passing arguments to the program<p>
+
+Command line argument passing is currently not supported for the Commodore
+610.
+
+
+
+<sect>Bugs/Feedback<p>
+
+If you have problems using the library, if you find any bugs, or if you're
+doing something interesting with it, I would be glad to hear from you. Feel
+free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
+name="uz@cc65.org">).
+
+
+
+<sect>License<p>
+
+This software is provided 'as-is', without any expressed or implied
+warranty. In no event will the authors be held liable for any damages
+arising from the use of this software.
+
+Permission is granted to anyone to use this software for any purpose,
+including commercial applications, and to alter it and redistribute it
+freely, subject to the following restrictions:
+
+<enum>
+<item> The origin of this software must not be misrepresented; you must not
+ claim that you wrote the original software. If you use this software
+ in a product, an acknowledgment in the product documentation would be
+ appreciated but is not required.
+<item> Altered source versions must be plainly marked as such, and must not
+ be misrepresented as being the original software.
+<item> This notice may not be removed or altered from any source
+ distribution.
+</enum>
+
+</article>
+
+
+
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