1 <!doctype linuxdoc system>
5 <title>Commodore 64 specific information for cc65
6 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
10 An overview over the C64 runtime system as it is implemented for the cc65 C
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 This file contains an overview of the C64 runtime system as it comes with the
22 cc65 C compiler. It describes the memory layout, C64 specific header files,
23 available drivers, and any pitfalls specific to that platform.
25 Please note that C64 specific functions are just mentioned here, they are
26 described in detail in the separate <htmlurl url="funcref.html" name="function
27 reference">. Even functions marked as "platform dependent" may be available on
28 more than one platform. Please see the function reference for more
32 <sect>Binary format<p>
34 The standard binary output format generated by the linker for the C64 target
35 is a machine language program with a one line BASIC stub, which calls the
36 machine language part via SYS. This means that a program can be loaded as
37 BASIC program and started with RUN. It is of course possible to change this
38 behaviour by using a modified startup file and linker config.
41 <sect>Memory layout<p>
43 cc65 generated programs with the default setup run with the I/O area and the
44 kernal ROM enabled (memory under the kernal may be used for graphics or as
45 extended memory - see the sections about graphics and extended memory
46 drivers). The BASIC ROM is disabled, which gives a usable memory range of
47 $0800 - $CFFF. This means that kernal entry points may be called
48 directly, but using the BASIC ROM is not possible without additional code.
54 The text screen is located at $400 (as in the standard setup).
57 The C runtime stack is located at $CFFF and growing downwards.
60 The C heap is located at the end of the program and grows towards the C
67 <sect>Platform specific header files<p>
69 Programs containing C64 specific code may use the <tt/c64.h/ or <tt/cbm.h/
70 header files. Using the later may be an option when writing code for more than
71 one CBM platform, since it includes <tt/c64.h/ and declares several functions
72 common to all CBM platforms.
75 <sect1>C64 specific functions<p>
77 The functions listed below are special for the C64. See the <htmlurl
78 url="funcref.html" name="function reference"> for declaration and usage.
85 <sect1>CBM specific functions<p>
87 Some functions are available for all (or at least most) of the Commodore
88 machines. See the <htmlurl url="funcref.html" name="function reference"> for
89 declaration and usage.
117 <sect1>Hardware access<p>
119 The following pseudo variables declared in the <tt/c64.h/ header file do allow
120 access to hardware located in the address space. Some variables are
121 structures, accessing the struct fields will access the chip registers.
126 The <tt/VIC/ structure allows access to the VIC II (the graphics
127 controller). See the <tt/_vic2.h/ header file located in the include
128 directory for the declaration of the structure.
131 The <tt/SID/ structure allows access to the SID (the sound interface
132 device). See the <tt/_sid.h/ header file located in the include directory
133 for the declaration of the structure.
135 <tag><tt/CIA1, CIA2/</tag>
136 Access to the two CIA (complex interface adapter) chips is available via
137 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
138 is explained in <tt/_6526.h/.
140 <tag><tt/COLOR_RAM/</tag>
141 A character array that mirrors the color RAM of the C64 at $D800.
147 <sect>Loadable drivers<p>
149 <sect1>Graphics drivers<p>
151 <em>Note:</em> All available graphics drivers for the TGI interface will use
152 the space below the I/O area and kernal ROM, so you can have hires graphics in
153 the standard setup without any memory loss or need for a changed
157 <tag><tt/c64-hi.tgi/</tag>
158 This driver features a resolution of 320*200 with two colors and an
159 adjustable palette (that means that the two colors can be chosen out of a
160 palette of the 16 C64 colors).
164 <sect1>Extended memory drivers<p>
168 <tag><tt/c64-georam.emd/</tag>
169 A driver for the Berkeley Softworks GeoRam cartridge. The driver will
170 determine the available RAM from the connected cartridge. It supports 64KB
173 <tag><tt/c64-ram.emd/</tag>
174 A driver for the hidden RAM below the I/O area and kernal ROM. Supports 48
175 256 byte pages. Please note that this driver is incompatible with any of the
178 <tag><tt/c64-ramcart.emd/</tag>
179 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
180 Will test the hardware for the available RAM.
182 <tag><tt/c64-reu.emd/</tag>
183 A driver for the CBM REUs. The driver will determine from the connected REU
184 if it supports 128KB of RAM or more. In the latter case, 256KB are assumed,
185 but since there are no range checks, the application can use more memory if
186 it has better knowledge about the hardware than the driver.
188 <tag><tt/c64-vdc.emd/</tag>
189 A driver for the VDC memory of the C128. Written and contributed by Maciej
190 Witkowiak. Can be used if the program is running in C64 mode of the C128.
191 Autodetects the amount of memory available (16 or 64K) and offers 64 or 256
192 pages of 256 bytes each.
194 <tag><tt/dtv-himem.emd/</tag>
195 A driver for the C64 D2TV (the second or PAL version). This driver offers
196 indeed 7680 pages of 256 bytes each.
201 <sect1>Joystick drivers<p>
205 <tag><tt/c64-hitjoy.joy/</tag>
206 Driver for the Digital Excess & Hitmen adapter contributed by Groepaz. See
207 <htmlurl url="http://www.digitalexcess.de/downloads/productions.php"
208 name="http://www.digitalexcess.de/downloads/productions.php"> on
209 instructions how to build one. Up to four joysticks are supported.
211 <tag><tt/c64-ptvjoy.joy/</tag>
212 Driver for the Protovision 4-player adapter contributed by Groepaz. See
213 <htmlurl url="http://www.protovision-online.de/hardw/hardwstart.htm"
214 name="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and
215 building instructions. Up to four joysticks are supported.
217 <tag><tt/c64-stdjoy.joy/</tag>
218 Supports up to two standard joysticks connected to the joysticks port of
221 <tag><tt/c64-numpad.joy/</tag>
222 Supports one joystick emulated by the numberpad of the C128 in C64 mode,
223 the firebutton is labeled &dquot;5&dquot; and ENTER.
228 <sect1>Mouse drivers<p>
232 <tag><tt/c64-1351.mou/</tag>
233 Supports a standard mouse connected to port #0 of the C64.
235 <tag><tt/c64-joy.mou/</tag>
236 Supports a mouse emulated by a standard joystick e.g. 1350 mouse in port
239 <tag><tt/c64-pot.mou/</tag>
240 Supports a potentiometer device e.g. Koala Pad connected to port #1 of
246 <sect1>RS232 device drivers<p>
250 <tag><tt/c64-swlink.ser/</tag>
251 Driver for the SwiftLink cartridge. Supports up to 38400 baud, hardware flow
252 control (RTS/CTS) and interrupt driven receives. Note that because of the
253 peculiarities of the 6551 chip together with the use of the NMI, transmits
254 are not interrupt driven, and the transceiver blocks if the receiver asserts
255 flow control because of a full buffer.
267 <sect1>Passing arguments to the program<p>
269 Command line arguments can be passed to <tt/main()/. Since this is not
270 supported by BASIC, the following syntax was chosen:
273 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
277 <item>Arguments are separated by spaces.
278 <item>Arguments may be quoted.
279 <item>Leading and trailing spaces around an argument are ignored. Spaces within
280 a quoted argument are allowed.
281 <item>The first argument passed to <tt/main/ is the program name.
282 <item>A maximum number of 10 arguments (including the program name) are
287 <sect1>Program return code<p>
289 The program return code (low byte) is passed back to BASIC by use of the
295 The runtime for the C64 uses routines marked as <tt/.CONDES/ type 2 for
296 interrupt handlers. Such routines must be written as simple machine language
297 subroutines and will be called automatically by the interrupt handler code
298 when they are linked into a program. See the discussion of the <tt/.CONDES/
299 feature in the <htmlurl url="ca65.html" name="assembler manual">.
303 <sect>Bugs/Feedback<p>
305 If you have problems using the library, if you find any bugs, or if you're
306 doing something interesting with it, I would be glad to hear from you. Feel
307 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
308 name="uz@cc65.org">).
314 This software is provided 'as-is', without any expressed or implied
315 warranty. In no event will the authors be held liable for any damages
316 arising from the use of this software.
318 Permission is granted to anyone to use this software for any purpose,
319 including commercial applications, and to alter it and redistribute it
320 freely, subject to the following restrictions:
323 <item> The origin of this software must not be misrepresented; you must not
324 claim that you wrote the original software. If you use this software
325 in a product, an acknowledgment in the product documentation would be
326 appreciated but is not required.
327 <item> Altered source versions must be plainly marked as such, and must not
328 be misrepresented as being the original software.
329 <item> This notice may not be removed or altered from any source