Commodore 128 specific information for cc65 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org"> <date>2003-12-14 <abstract> An overview over the C128 runtime system as it is implemented for the cc65 C compiler. </abstract>  <toc>  <sect>Overview This file contains an overview of the C128 runtime system as it comes with the cc65 C compiler. It describes the memory layout, C128 specific header files, available drivers, and any pitfalls specific to that platform. Please note that C128 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. <sect>Binary format The standard binary output format generated by the linker for the C128 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 I/O area and the kernal ROM enabled. Note that this is a non standard memory layout, and that there is no "memory configuration index" for this layout. This means that special case has to be taken when changing the configuration, or calling any code that does this. The memory configuration register at $FF00 should be saved and restored instead of relying on the memory configuration index stored in the zero page. The setup gives a usable memory range of $1C00 - $CFFF. Having just the kernal ROM mapped in means, that kernal entry points may be called directly, but using the BASIC ROM is not possible without additional code. Special locations: <descrip> <tag/Text screen/ The text screen is located at $400 (as in the standard setup). <tag/Stack/ The C runtime stack is located at $CFFF 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 C128 specific code may use the <tt/c128.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/c128.h/ and declares several functions common to all CBM platforms. <sect1>C128 specific functions The functions listed below are special for the C128. See the <htmlurl url="funcref.html" name="function reference"> for declaration and usage. <itemize> <item>toggle_videomode <item>c64mode <item>fast <item>slow </itemize> <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/c128.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/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/VDC/</tag> The <tt/VDC/ structure allows access to the VDC (the video display controller). See the <tt/_vdc.h/ header file located in the include directory for the declaration of the structure. <tag><tt/CIA1, CIA2/</tag> Access to the two CIA (complex interface adapater) chips is available via the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables is explained in <tt/_cia.h/. <tag><tt/COLOR_RAM/</tag> A character array that mirrors the color RAM of the C64 at $D800. </descrip> <sect>Loadable drivers <sect1>Graphics drivers Note: The graphics drivers for the VDC are incompatible with the extended memory drivers using the VDC memory! <descrip> <tag><tt/c128-vdc.tgi/</tag> This driver was written by Maciej Witkowiak. It uses the 80 column display and features a resolution of 640*200 with two colors and an adjustable palette (that means that the two colors can be choosen out of the 16 VDC colors). <tag><tt/c128-vdc2.tgi/</tag> This driver was written by Maciej Witkowiak. This driver uses the 80 column display and features a resolution of 640*480 with two colors and an adjustable palette (that means that the two colors can be choosen out of the 16 VDC colors). The driver requires 64KB VDC RAM. </descrip> Note: The colors are translated from definitions in headers to correct VDC values so please use definitions or VIC color numbers only. Colors <tt/GRAY3/ and <tt/BROWN/ are missing on VDC and are translated to the two colors missing from VIC palette. <sect1>Extended memory drivers <descrip> <tag><tt/c128-georam.emd/</tag> A driver for the GeoRam cartridge. The driver will always assume 2048 pages of 256 bytes each. There are no checks, so if your program knows better, just go ahead. <tag><tt/c128-ram.emd/</tag> An extended memory driver for the RAM in page 1. The common memory area is excluded, so this driver supports 251 pages of 256 bytes each. <tag><tt/c128-ramcart.emd/</tag> A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak. Will test the hardware for the available RAM. <tag><tt/c128-reu.emd/</tag> A driver for the CBM REUs. The driver will determine from the connected REU if it supports 128KB of RAM or more. In the latter case, 256KB are assumed, but since there are no range checks, the application can use more memory if it has better knowledge about the hardware than the driver. <tag><tt/c128-vdc.emd/</tag> A driver for the VDC memory of the C128 written and contributed by Maciej Witkowiak. Autodetects the amount of memory available (16 or 64K) and offers 64 or 256 pages of 256 bytes each. Note: This driver is incompatible with any of the graphics drivers using the VDC! </descrip> <sect1>Joystick drivers <descrip> <tag><tt/c128-ptvjoy.joy/</tag> Driver for the Protovision 4-player adapter originally written by Groepaz for the C64 and converted for the C128 by me. See <htmlurl url="http://www.protovision-online.de/hardw/hardwstart.htm" name="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and building instructions. Up to four joysticks are supported. <tag><tt/c128-stdjoy.joy/</tag> Supports up to two joysticks connected to the standard joysticks port of the C128. </descrip> <sect1>Mouse drivers Currently no drivers available (in fact, the API for loadable mouse drivers does not exist). <sect1>RS232 device drivers <descrip> <tag><tt/c128-swlink.ser/</tag> Driver for the SwiftLink cartridge. Supports up to 38400 baud, hardware flow control (RTS/CTS) and interrupt driven receives. Note that because of the peculiarities of the 6551 chip together with the use of the NMI, transmits are not interrupt driven, and the transceiver blocks if the receiver asserts flow control because of a full buffer. The driver uses the RS232 variables and buffers of the kernal (buffers at $C00 and $D00). </descrip> <sect>Limitations <sect>Other hints <sect1>Passing arguments to the program Command line argument passing is currently not supported for the C128. <sect1>Program return code The program return code (low byte) is passed back to BASIC by use of the <tt/ST/ variable. <sect1>Interrupts The runtime for the C128 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 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>