1 <!doctype linuxdoc system>
5 <title>Commodore 64-specific information for cc65
6 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">
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 <url 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
66 <sect>Linker configurations<p>
68 The ld65 linker comes with a default config file for the Commodore 64,
69 which is used via <tt/-t c64/. The
70 c64 package comes with additional secondary linker config files, which are
71 used via <tt/-t c64 -C <configfile>/.
74 <sect1>default config file (<tt/c64.cfg/)<p>
76 The default configuration is tailored to C programs. It supplies the load
77 address and a small BASIC stub that starts the compiled program using a SYS
81 <sect1><tt/c64-asm.cfg/<p>
83 This configuration is made for assembler programmers who don't need a special
84 setup. The default start address is $801. It can be changed with the
85 linker command line option <tt/--start-addr/. All standard segments with the
86 exception of <tt/zeropage/ are written to the output file and a two byte load
89 To use this config file, assemble with <tt/-t c64/ and link with <tt/-C
90 c64-asm.cfg/. The former will make sure that correct character translation is
91 in effect, while the latter supplies the actual config. When using <tt/cl65/,
92 use both command line options.
94 Sample command line for <tt/cl65/:
97 cl65 -o file.prg -t c64 -C c64-asm.cfg source.s
100 To generate code that loads to $C000:
103 cl65 -o file.prg --start-addr $C000 -t c64 -C c64-asm.cfg source.s
106 It is also possible to add a small BASIC header to the program, that uses SYS
107 to jump to the program entry point (which is the start of the code segment).
108 The advantage is that the program can be started using RUN.
110 To generate a program with a BASIC SYS header, use
113 cl65 -o file.prg -u __EXEHDR__ -t c64 -C c64-asm.cfg source.s
116 Please note that in this case a changed start address doesn't make sense,
117 since the program must be loaded to the BASIC start address.
121 <sect1>80 Columns conio driver<p>
123 The C64 package comes with an alternative software driven 80 columns
124 module <tt/c64-soft80.o/ which uses the memory under I/O between $d000
127 In memory constrained situations the memory from $400 to $7FF
128 can be made available to a program by calling <tt/_heapadd ((void *) 0x0400, 0x0400);/
129 at the beginning of <tt/main()/. Doing so is beneficial even if the program
130 doesn't use the the heap explicitly because loading a driver uses the heap implicitly.
132 Using <tt/c64-soft80.o/ is as simple as placing it on the linker command
136 cl65 -t c64 myprog.c c64-soft80.o
139 Note that the soft80 conio driver is incompatible with the
140 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
141 <tt/c64-hi.tgi (c64_hi_tgi)/ graphics driver.
143 <sect2>80 Columns conio driver (monochrome)<p>
145 In an (even more) memory constrained situation, a size optimized version of the
146 software driven 80 columns module may be used, which only supports one common
147 text color for the whole screen.
150 cl65 -t c64 myprog.c c64-soft80mono.o
153 <sect>Platform-specific header files<p>
155 Programs containing C64-specific code may use the <tt/c64.h/ or <tt/cbm.h/
156 header files. Using the later may be an option when writing code for more than
157 one CBM platform, since it includes <tt/c64.h/ and declares several functions
158 common to all CBM platforms.
161 <sect1>C64-specific functions<p>
163 The functions listed below are special for the C64. See the <url
164 url="funcref.html" name="function reference"> for declaration and usage.
171 <sect1>CBM-specific functions<p>
173 Some functions are available for all (or at least most) of the Commodore
174 machines. See the <url url="funcref.html" name="function reference"> for
175 declaration and usage.
203 <sect1>Hardware access<p>
205 The following pseudo variables declared in the <tt/c64.h/ header file do allow
206 access to hardware located in the address space. Some variables are
207 structures, accessing the struct fields will access the chip registers.
212 The <tt/VIC/ structure allows access to the VIC II (the graphics
213 controller). See the <tt/_vic2.h/ header file located in the include
214 directory for the declaration of the structure.
217 The <tt/SID/ structure allows access to the SID (the sound interface
218 device). See the <tt/_sid.h/ header file located in the include directory
219 for the declaration of the structure.
221 <tag><tt/CIA1, CIA2/</tag>
222 Access to the two CIA (complex interface adapter) chips is available via
223 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
224 is explained in <tt/_6526.h/.
226 <tag><tt/COLOR_RAM/</tag>
227 A character array that mirrors the color RAM of the C64 at $D800.
233 <sect>Loadable drivers<p>
235 The names in the parentheses denote the symbols to be used for static linking of the drivers.
238 <sect1>Graphics drivers<p>
240 <em>Note:</em> All available graphics drivers for the TGI interface will use
241 the space below the I/O area and kernal ROM, so you can have hires graphics in
242 the standard setup without any memory loss or need for a changed
246 <tag><tt/c64-hi.tgi (c64_hi_tgi)/</tag>
247 This driver features a resolution of 320*200 with two colors and an
248 adjustable palette (that means that the two colors can be chosen out of a
249 palette of the 16 C64 colors).
252 Note that the graphics drivers are incompatible with the
253 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
254 <tt/c64-soft80.o/ software 80 columns conio driver.
256 <sect1>Extended memory drivers<p>
260 <tag><tt/c64-c256k.emd (c64_c256k_emd)/</tag>
261 A driver for the C64 256K memory expansion. This driver offers 768 pages of
262 256 bytes each. Written and contributed by Marco van den Heuvel.
264 <tag><tt/c64-dqbb.emd (c64_dqbb_emd)/</tag>
265 A driver for the Double Quick Brown Box cartridge. This driver offers
266 64 pages of 256 bytes each. Written and contributed by Marco van den Heuvel.
268 <tag><tt/c64-georam.emd (c64_georam_emd)/</tag>
269 A driver for the Berkeley Softworks GeoRam cartridge. The driver will
270 determine the available RAM from the connected cartridge. It supports 64KB
273 <tag><tt/c64-isepic.emd (c64_isepic_emd)/</tag>
274 A driver for the ISEPIC cartridge. This driver offers just 8 pages of 256
275 bytes each. Written and contributed by Marco van den Heuvel.
277 <tag><tt/c64-ram.emd (c64_ram_emd)/</tag>
278 A driver for the hidden RAM below the I/O area and kernal ROM. Supports 48
279 256 byte pages. Please note that this driver is incompatible with any of the
280 graphics drivers, or the soft80 conio driver!
282 <tag><tt/c64-ramcart.emd (c64_ramcart_emd)/</tag>
283 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
284 Will test the hardware for the available RAM.
286 <tag><tt/c64-reu.emd (c64_reu_emd)/</tag>
287 A driver for the CBM REUs. The driver will determine from the connected REU
288 if it supports 128KB of RAM or more. In the latter case, 256KB are assumed,
289 but since there are no range checks, the application can use more memory if
290 it has better knowledge about the hardware than the driver.
292 <tag><tt/c64-vdc.emd (c64_vdc_emd)/</tag>
293 A driver for the VDC memory of the C128. Written and contributed by Maciej
294 Witkowiak. Can be used if the program is running in C64 mode of the C128.
295 Autodetects the amount of memory available (16 or 64K) and offers 64 or 256
296 pages of 256 bytes each.
298 <tag><tt/dtv-himem.emd (dtv_himem_emd)/</tag>
299 A driver for the C64 D2TV (the second or PAL version). This driver offers
300 indeed 7680 pages of 256 bytes each.
305 <sect1>Joystick drivers<p>
307 The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/c64-stdjoy.joy (c64_stdjoy_joy)/.
311 <tag><tt/c64-hitjoy.joy (c64_hitjoy_joy)/</tag>
312 Driver for the Digital Excess & Hitmen adapter contributed by Groepaz.
313 See <url url="http://www.digitalexcess.de/downloads/productions.php"> on
314 instructions how to build one. Up to four joysticks are supported.
316 <tag><tt/c64-ptvjoy.joy (c64_ptvjoy_joy)/</tag>
317 Driver for the Protovision 4-player adapter contributed by Groepaz. See
318 <url url="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and
319 building instructions. Up to four joysticks are supported.
321 <tag><tt/c64-stdjoy.joy (c64_stdjoy_joy)/</tag>
322 Supports up to two standard joysticks connected to the joysticks port of
325 <tag><tt/c64-numpad.joy (c64_numpad_joy)/</tag>
326 Supports one joystick emulated by the numberpad of the C128 in C64 mode,
327 the firebutton is labeled &dquot;5&dquot; and ENTER.
332 <sect1>Mouse drivers<p>
334 The default drivers, <tt/mouse_stddrv (mouse_static_stddrv)/, point to <tt/c64-1351.mou (c64_1351_mou)/.
338 <tag><tt/c64-1351.mou (c64_1351_mou)/</tag>
339 Supports a standard mouse connected to port #0 of the C64.
341 <tag><tt/c64-inkwell.mou (c64_inkwell_mou)/</tag>
342 Supports the Inkwell Systems lightpens, connected to port #0 of the C64.
343 It can read both the one-button 170-C and the two-button 184-C pens. (It can
344 read other lightpens and light-guns that send their button signal to the
345 joystick left-button pin or the paddle Y [up/down] pin.)
347 <tag><tt/c64-joy.mou (c64_joy_mou)/</tag>
348 Supports a mouse emulated by a standard joystick, e.g. 1350 mouse, in port
351 <tag><tt/c64-pot.mou (c64_pot_mou)/</tag>
352 Supports a potentiometer device, e.g. Koala Pad, connected to port #1 of
358 <sect1>RS232 device drivers<p>
362 <tag><tt/c64-swlink.ser (c64_swlink_ser)/</tag>
363 Driver for the SwiftLink cartridge. Supports up to 38400 BPS, hardware flow
364 control (RTS/CTS), and interrupt-driven receives. Note that, because of the
365 peculiarities of the 6551 chip, together with the use of the NMI, transmits
366 are not interrupt driven; and, the transceiver blocks if the receiver asserts
367 flow control because of a full buffer.
380 <sect1>Escape code<p>
382 For an Esc, press CTRL and the <tt/[/ key.
385 <sect1>Passing arguments to the program<p>
387 Command-line arguments can be passed to <tt/main()/. Since this is not
388 supported directly by BASIC, the following syntax was chosen:
391 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
395 <item>Arguments are separated by spaces.
396 <item>Arguments may be quoted.
397 <item>Leading and trailing spaces around an argument are ignored. Spaces within
398 a quoted argument are allowed.
399 <item>The first argument passed to <tt/main()/ is the program name.
400 <item>A maximum number of 10 arguments (including the program name) are
405 <sect1>Program return code<p>
407 The program return code (low byte) is passed back to BASIC by use of the
413 The runtime for the C64 uses routines marked as <tt/.INTERRUPTOR/ for
414 interrupt handlers. Such routines must be written as simple machine language
415 subroutines and will be called automatically by the interrupt handler code
416 when they are linked into a program. See the discussion of the <tt/.CONDES/
417 feature in the <url url="ca65.html" name="assembler manual">.
423 This software is provided 'as-is', without any expressed or implied
424 warranty. In no event will the authors be held liable for any damages
425 arising from the use of this software.
427 Permission is granted to anyone to use this software for any purpose,
428 including commercial applications, and to alter it and redistribute it
429 freely, subject to the following restrictions:
432 <item> The origin of this software must not be misrepresented; you must not
433 claim that you wrote the original software. If you use this software
434 in a product, an acknowledgment in the product documentation would be
435 appreciated but is not required.
436 <item> Altered source versions must be plainly marked as such, and must not
437 be misrepresented as being the original software.
438 <item> This notice may not be removed or altered from any source