Commodore 16/116 specific information for cc65 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org"> <date>2003-12-15 <abstract> An overview over the C16 runtime system as it is implemented for the cc65 C compiler. </abstract>  <toc>  <sect>Overview This file contains an overview of the C16 runtime system as it comes with the cc65 C compiler. It describes the memory layout, C16/116 specific header files, available drivers, and any pitfalls specific to that platform. Please note that C16 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. Since the C16/C116 and the Commodore Plus/4 are almost identical (the former don't have the 6551 ACIA and only 16KB of memory), the <htmlurl url="plus4.html" name="Plus/4 documentation"> is also worth a look. The difference between both cc65 targets is that the Plus/4 runtime uses banking to support full 64K RAM, while the C16 does not use banking and supports up to 32K RAM. Because banking is not needed, most C16 programs will be somewhat smaller than the same program compiled for the Plus/4. However, programs C16 will always run on the Plus/4, while the reverse is not necessarily true. <sect>Binary format The standard binary output format generated by the linker for the C16/C116 target is a machine language program with a one line 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 cc65 generated programs with the default setup run with the kernal and basic banked out. This gives a usable memory range of $1000 - $4000 (or $8000 i the machine is equipped with 32K RAM or more). Having the kernal and basic ROMs banked out means, that no ROM entry points may be called directly from user code. Special locations: <descrip> <tag/Text screen/ The text screen is located at $C00 (as in the standard setup). <tag/Color RAM/ The color RAM is located at $800 (standard location). <tag/Stack/ The C runtime stack is located at $3FFF ($7FFF in case of a machine with 32K of memory or more) and growing downwards. <tag/Heap/ The C heap is located at the end of the program and grows towards the C runtime stack. </descrip> <sect>Platform specific header files Programs containing C16 specific code may use the <tt/c16.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/c16.h/ and declares several functions common to all CBM platforms. Please note that most of the header file declarations from the <tt/c16.h/ header file are shared between the C16 and Plus/4 configurations. For this reason, most of it is located in a common header file named <tt/cbm264.h/. <sect1>C16/C116 specific functions There are currently no special C16/C116 functions. <sect1>CBM specific functions 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 The following pseudo variables declared in the <tt/c16.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. <descrip> <tag><tt/TED/</tag> The <tt/TED/ structure allows access to the TED chip. See the <tt/_ted.h/ header file located in the include directory for the declaration of the structure. <tag><tt/COLOR_RAM/</tag> A character array that mirrors the color RAM of the C16 at $0800. </descrip> <sect>Loadable drivers <sect1>Graphics drivers No graphics drivers are currently available for the C16/C116. <sect1>Extended memory drivers <descrip> <tag><tt/c16-ram.emd/</tag> A driver for the hidden RAM below the BASIC and KERNAL ROMs. Supports 125 pages with 256 bytes each if the machine is equipped with 64K of memory (a Plus/4 or a memory extended C16/116). </descrip> <sect1>Joystick drivers <descrip> <tag><tt/c16-stdjoy.joy/</tag> Supports up to two joysticks connected to the standard joysticks port of the Commodore 16/116. </descrip> <sect1>Mouse drivers Currently no drivers available (in fact, the API for loadable mouse drivers does not exist). <sect1>RS232 device drivers The Commodore 16 does not have a builtin ACIA and no RS232 extensions are known. For this reason, there are no RS232 drivers available. Please note that the standard Plus/4 driver will not run together with the C16 library, because the latter does not support interrupts needed by the driver. <sect>Limitations <sect>Other hints <sect1>Passing arguments to the program Command line argument passing is currently not supported for the C16/C116. <sect1>Program return code The program return code (low byte) is passed back to BASIC by use of the <tt/ST/ variable. <sect>Bugs/Feedback 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 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>