--- /dev/null
+<!doctype linuxdoc system>
+
+<article>
+
+<title>Commodore 510 (aka P500) specific information for cc65
+<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
+Stefan A. Haubenthal, <htmlurl url="mailto:polluks@sdf.lonestar.org" name="polluks@sdf.lonestar.org">
+<date>2006-05-22
+
+<abstract>
+An overview over the Commodore 510 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 510 runtime system as it comes with
+the cc65 C compiler. It describes the memory layout, CBM 510 specific header
+files, available drivers, and any pitfalls specific to that platform.
+
+Please note that CBM 510 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 510 (named P128 in the U.S.), no other
+machines are supported by this cc65 target.
+
+
+
+<sect>Binary format<p>
+
+The standard binary output format generated by the linker for the CBM510
+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 510 run in bank 0, 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 510 allocates all memory between
+$0002 and $FFF0 in bank 0 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 pages are lost in high memory, because the runtime sets up a copy of the
+character ROM, a text screen and a CBM compatible jump table at $FF81.
+The main startup code is located at $0400, so about 54K of the complete
+bank are actually usable 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 510 specific code may use the <tt/cbm510.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/cbm510.h/ and declares
+several functions common to all CBM platforms.
+
+<sect1>CBM 510 specific functions<p>
+
+The functions listed below are special for the CBM 510. See the <htmlurl
+url="funcref.html" name="function reference"> for declaration and usage.
+
+<itemize>
+<item>peekbsys
+<item>peekwsys
+<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.
+
+
+<itemize>
+<item>cbm_close
+<item>cbm_closedir
+<item>cbm_k_setlfs
+<item>cbm_k_setnam
+<item>cbm_k_load
+<item>cbm_k_save
+<item>cbm_k_open
+<item>cbm_k_close
+<item>cbm_k_readst
+<item>cbm_k_chkin
+<item>cbm_k_ckout
+<item>cbm_k_basin
+<item>cbm_k_bsout
+<item>cbm_k_clrch
+<item>cbm_load
+<item>cbm_open
+<item>cbm_opendir
+<item>cbm_read
+<item>cbm_readdir
+<item>cbm_save
+<item>cbm_write
+<item>get_tv
+</itemize>
+
+
+
+<sect1>Hardware access<p>
+
+The following pseudo variables declared in the <tt/cbm510.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/peekwsys/, <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/VIC/</tag>
+ The <tt/VIC/ structure allows access to the VIC II (the graphics
+ controller). See the <tt/_vic2.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>
+
+
+<sect1>Graphics drivers<p>
+
+No graphics drivers are currently available for the Commodore 510.
+
+
+<sect1>Extended memory drivers<p>
+
+<descrip>
+ <tag><tt/cbm510-ram.emd/</tag>
+ A driver for the RAM in bank 1. Supports up to 255 pages with 256 bytes
+ each.
+</descrip><p>
+
+
+<sect1>Joystick drivers<p>
+
+<descrip>
+
+ <tag><tt/cbm510-std.joy/</tag>
+ Supports up to two standard joysticks connected to the joysticks port of
+ the Commodore 510.
+
+</descrip><p>
+
+
+<sect1>Mouse drivers<p>
+
+No mouse drivers are currently available for the Commodore 510.
+
+
+<sect1>RS232 device drivers<p>
+
+<descrip>
+
+ <tag><tt/cbm510-std.ser/</tag>
+ Driver for the 6551 ACIA chip built into the Commodore 510. Supports up to
+ 19200 baud, hardware flow control (RTS/CTS) and interrupt driven receives.
+ Note that because of the peculiarities of the 6551 chip transmits are not
+ interrupt driven, and the transceiver blocks if the receiver asserts flow
+ control because of a full buffer.
+
+</descrip><p>
+
+
+<sect>Limitations<label id="limitations"><p>
+
+
+<sect1>Kernal and hardware access<p>
+
+Since the program runs in bank 0, and the kernal and all I/O chips are located
+in bank 15, calling ROM routines or accessing hardware needs special code. The
+cc65 runtime implements wrappers for all functions in the kernal jump table.
+While this simplifies things, it should be noted that the wrappers do have
+quite an impact on performance: A cross bank call has an extra 300µs
+penalty added by the wrapper.
+
+<sect1>Interrupts<p>
+
+Compiled programs contain an interrupt handler that runs in the program bank.
+This has several advantages, one of them being performance (see cross bank
+call overhead mentioned above). However, this introduces one problem:
+Interrupts are lost while the CPU executes code in the kernal bank. As a
+result, the clock may go wrong and (worse) serial interrupts may get lost.
+
+Since the cc65 runtime does only call the kernal for disk I/O, this means that
+a program should not do file I/O while it depends on interrupts.
+
+
+<sect>Other hints<p>
+
+<sect1>Passing arguments to the program<p>
+
+Command line argument passing is currently not supported for the Commodore
+510.
+
+
+<sect1>Program return code<p>
+
+The program return code (signed char) is passed back to BASIC by use of the
+<tt/ST/ variable.
+
+
+<sect1>Interrupts<p>
+
+The runtime for the Commodore 510 uses routines marked as <tt/.CONDES/ type 2
+for interrupt handlers. Such routines must be written as simple machine
+language subroutines and will be called automatically by the interrupt handler
+code when they are linked into a program. See the discussion of the
+<tt/.CONDES/ feature in the <htmlurl url="ca65.html" name="assembler manual">.
+
+
+
+<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>
projects / cc65 / commitdiff