1 <!doctype linuxdoc system>
5 <title>Commodore 64-specific information for cc65
6 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz"><newline>
7 <url url="mailto:greg.king5@verizon.net" name="Greg King">
11 An overview over the C64 runtime system as it is implemented for the cc65 C
15 <!-- Table of contents -->
18 <!-- Begin the document -->
22 This file contains an overview of the C64 runtime system as it comes with the
23 cc65 C compiler. It describes the memory layout, C64-specific header files,
24 available drivers, and any pitfalls specific to that platform.
26 Please note that C64-specific functions are just mentioned here, they are
27 described in detail in the separate <url url="funcref.html" name="function
28 reference">. Even functions marked as "platform dependent" may be available on
29 more than one platform. Please see the function reference for more
33 <sect>Binary format<p>
35 The standard binary output format generated by the linker for the C64 target
36 is a machine language program with a one line BASIC stub, which calls the
37 machine language part via SYS. This means that a program can be loaded as
38 BASIC program and started with RUN. It is of course possible to change this
39 behaviour by using a modified startup file and linker config.
42 <sect>Memory layout<p>
44 cc65 generated programs with the default setup run with the I/O area and the
45 kernal ROM enabled (memory under the kernal may be used for graphics or as
46 extended memory - see the sections about graphics and extended memory
47 drivers). The BASIC ROM is disabled, which gives a usable memory range of
48 $0800 - $CFFF. This means that kernal entry points may be called
49 directly, but using the BASIC ROM is not possible without additional code.
55 The text screen is located at $400 (as in the standard setup).
58 The C runtime stack is located at $CFFF and growing downwards.
61 The C heap is located at the end of the program and grows towards the C
67 <sect>Linker configurations<p>
69 The ld65 linker comes with a default config file for the Commodore 64,
70 which is used via <tt/-t c64/. The
71 c64 package comes with additional secondary linker config files, which are
72 used via <tt/-t c64 -C <configfile>/.
75 <sect1>default config file (<tt/c64.cfg/)<p>
77 The default configuration is tailored to C programs. It supplies the load
78 address and a small BASIC stub that starts the compiled program using a SYS
82 <sect1><tt/c64-asm.cfg/<p>
84 This configuration is made for assembler programmers who don't need a special
85 setup. The default start address is $801. It can be changed with the
86 linker command line option <tt/--start-addr/. All standard segments with the
87 exception of <tt/zeropage/ are written to the output file and a two byte load
90 To use this config file, assemble with <tt/-t c64/ and link with <tt/-C
91 c64-asm.cfg/. The former will make sure that correct character translation is
92 in effect, while the latter supplies the actual config. When using <tt/cl65/,
93 use both command line options.
95 Sample command line for <tt/cl65/:
98 cl65 -o file.prg -t c64 -C c64-asm.cfg source.s
101 To generate code that loads to $C000:
104 cl65 -o file.prg --start-addr $C000 -t c64 -C c64-asm.cfg source.s
107 It is also possible to add a small BASIC header to the program, that uses SYS
108 to jump to the program entry point (which is the start of the code segment).
109 The advantage is that the program can be started using RUN.
111 To generate a program with a BASIC SYS header, use
114 cl65 -o file.prg -u __EXEHDR__ -t c64 -C c64-asm.cfg source.s
117 Please note that in this case a changed start address doesn't make sense,
118 since the program must be loaded to the BASIC start address.
122 <sect1>80 Columns conio driver<p>
124 The C64 package comes with an alternative software driven 80 columns
125 module <tt/c64-soft80.o/ which uses the memory under I/O between $d000
128 In memory constrained situations the memory from $400 to $7FF
129 can be made available to a program by calling <tt/_heapadd ((void *) 0x0400, 0x0400);/
130 at the beginning of <tt/main()/. Doing so is beneficial even if the program
131 doesn't use the the heap explicitly because loading a driver uses the heap implicitly.
133 Using <tt/c64-soft80.o/ is as simple as placing it on the linker command
137 cl65 -t c64 myprog.c c64-soft80.o
140 Note that the soft80 conio driver is incompatible with the
141 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
142 <tt/c64-hi.tgi (c64_hi_tgi)/ graphics driver.
144 <sect2>80 Columns conio driver (monochrome)<p>
146 In an (even more) memory constrained situation, a size optimized version of the
147 software driven 80 columns module may be used, which only supports one common
148 text color for the whole screen.
151 cl65 -t c64 myprog.c c64-soft80mono.o
154 <sect>Platform-specific header files<p>
156 Programs containing C64-specific code may use the <tt/c64.h/ or <tt/cbm.h/
157 header files. Using the later may be an option when writing code for more than
158 one CBM platform, since it includes <tt/c64.h/ and declares several functions
159 common to all CBM platforms.
162 <sect1>C64-specific functions<p>
164 The functions listed below are special for the C64. See the <url
165 url="funcref.html" name="function reference"> for declaration and usage.
172 <sect1>C64-specific accelerator functions<p>
174 The functions listed below are accelerator functions for the C64. See the <url
175 url="funcref.html" name="function reference"> for declaration and usage.
184 <sect1>CBM-specific functions<p>
186 Some functions are available for all (or at least most) of the Commodore
187 machines. See the <url url="funcref.html" name="function reference"> for
188 declaration and usage.
216 <sect1>Hardware access<p>
218 The following pseudo variables declared in the <tt/c64.h/ header file do allow
219 access to hardware located in the address space. Some variables are
220 structures, accessing the struct fields will access the chip registers.
225 The <tt/VIC/ structure allows access to the VIC II (the graphics
226 controller). See the <tt/_vic2.h/ header file located in the include
227 directory for the declaration of the structure.
230 The <tt/SID/ structure allows access to the SID (the sound interface
231 device). See the <tt/_sid.h/ header file located in the include directory
232 for the declaration of the structure.
234 <tag><tt/CIA1, CIA2/</tag>
235 Access to the two CIA (complex interface adapter) chips is available via
236 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
237 is explained in <tt/_6526.h/.
239 <tag><tt/COLOR_RAM/</tag>
240 A character array that mirrors the color RAM of the C64 at $D800.
246 <sect>Loadable drivers<p>
248 The names in the parentheses denote the symbols to be used for static linking of the drivers.
251 <label id="graphics-drivers">
252 <sect1>Graphics drivers<p>
254 <em>Note:</em> All available graphics drivers for the TGI interface will use
255 the space below the I/O area and Kernal ROM; so, you can have hires graphics in
256 the standard setup without any memory loss or need for a changed configuration.
258 You can use a mouse driver at the same time that you use a TGI driver. But, if
259 you want to see the default mouse pointer on the graphics screen, then you
260 explicitly must link a special object file into your program. It will put the
261 arrow into the "high RAM" area where the bitmaps are put. Its name is
262 "<tt/c64-tgimousedata.o/". Example:
265 cl65 -t c64 -o program-file main-code.c subroutines.s c64-tgimousedata.o
269 <tag><tt/c64-hi.tgi (c64_hi_tgi)/</tag>
270 This driver features a resolution of 320*200 with two colors and an
271 adjustable palette (that means that the two colors can be chosen out of a
272 palette of the 16 C64 colors).
275 Note that the graphics drivers are incompatible with the
276 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
277 <tt/c64-soft80.o/ software 80-columns conio driver.
280 <sect1>Extended memory drivers<p>
284 <tag><tt/c64-65816.emd (c64_65816_emd)/</tag>
285 Extended memory driver for 65816 (eg SCPU) based extra RAM.
286 Written and contributed by Marco van den Heuvel.
288 <tag><tt/c64-c256k.emd (c64_c256k_emd)/</tag>
289 A driver for the C64 256K memory expansion. This driver offers 768 pages of
290 256 bytes each. Written and contributed by Marco van den Heuvel.
292 <tag><tt/c64-dqbb.emd (c64_dqbb_emd)/</tag>
293 A driver for the Double Quick Brown Box cartridge. This driver offers
294 64 pages of 256 bytes each. Written and contributed by Marco van den Heuvel.
296 <tag><tt/c64-georam.emd (c64_georam_emd)/</tag>
297 A driver for the Berkeley Softworks GeoRam cartridge. The driver will
298 determine the available RAM from the connected cartridge. It supports 64KB
301 <tag><tt/c64-isepic.emd (c64_isepic_emd)/</tag>
302 A driver for the ISEPIC cartridge. This driver offers just 8 pages of 256
303 bytes each. Written and contributed by Marco van den Heuvel.
305 <tag><tt/c64-ram.emd (c64_ram_emd)/</tag>
306 A driver for the hidden RAM below the I/O area and kernal ROM. Supports 48
307 256 byte pages. Please note that this driver is incompatible with any of the
308 graphics drivers, or the soft80 conio driver!
310 <tag><tt/c64-ramcart.emd (c64_ramcart_emd)/</tag>
311 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
312 Will test the hardware for the available RAM.
314 <tag><tt/c64-reu.emd (c64_reu_emd)/</tag>
315 A driver for the CBM REUs. The driver will test the connected REU to find
316 out how much RAM is present.
318 <tag><tt/c64-vdc.emd (c64_vdc_emd)/</tag>
319 A driver for the VDC memory of the C128. Written and contributed by Maciej
320 Witkowiak. Can be used if the program is running in C64 mode of the C128.
321 Autodetects the amount of memory available (16 or 64K) and offers 64 or 256
322 pages of 256 bytes each.
324 <tag><tt/dtv-himem.emd (dtv_himem_emd)/</tag>
325 A driver for the C64 D2TV (the second or PAL version). This driver offers
326 indeed 7680 pages of 256 bytes each.
331 <sect1>Joystick drivers<p>
333 The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/c64-stdjoy.joy (c64_stdjoy_joy)/.
337 <tag><tt/c64-hitjoy.joy (c64_hitjoy_joy)/</tag>
338 Driver for the Digital Excess & Hitmen adapter contributed by Groepaz.
339 See <url url="http://www.digitalexcess.de/downloads/productions.php"> on
340 instructions how to build one. Up to four joysticks are supported.
342 <tag><tt/c64-ptvjoy.joy (c64_ptvjoy_joy)/</tag>
343 Driver for the Protovision 4-player adapter contributed by Groepaz. See
344 <url url="http://www.protovision-online.de/hardw/4_player.php?language=en"
345 name="Protovision shop"> for prices and building instructions. Up to four
346 joysticks are supported.
348 <tag><tt/c64-stdjoy.joy (c64_stdjoy_joy)/</tag>
349 Supports up to two standard joysticks connected to the joysticks port of
352 <tag><tt/c64-numpad.joy (c64_numpad_joy)/</tag>
353 Supports one joystick emulated by the numberpad of the C128 in C64 mode,
354 the firebutton is labeled &dquot;5&dquot; and ENTER.
359 <sect1>Mouse drivers<p>
361 You can use these drivers in text-mode or graphics-mode (TGI) programs. See
362 the description of <ref id="graphics-drivers" name="the graphics drivers">.
364 The default drivers, <tt/mouse_stddrv (mouse_static_stddrv)/, point to <tt/c64-1351.mou (c64_1351_mou)/.
368 <tag><tt/c64-1351.mou (c64_1351_mou)/</tag>
369 Supports a standard mouse connected to port #0 of the C64.
371 <tag><tt/c64-inkwell.mou (c64_inkwell_mou)/</tag>
372 Supports the Inkwell Systems lightpens, connected to port #0 of the C64.
373 It can read both the one-button 170-C and the two-button 184-C pens. (It can
374 read other lightpens and light-guns that send their button signal to the
375 joystick left-button pin or the paddle Y [up/down] pin.)
377 <tag><tt/c64-joy.mou (c64_joy_mou)/</tag>
378 Supports a mouse emulated by a standard joystick, e.g. 1350 mouse, in port
381 <tag><tt/c64-pot.mou (c64_pot_mou)/</tag>
382 Supports a potentiometer device, e.g. Koala Pad, connected to port #1 of
388 <sect1>RS232 device drivers<p>
392 <tag><tt/c64-swlink.ser (c64_swlink_ser)/</tag>
393 Driver for the SwiftLink cartridge. Supports up to 38400 BPS, hardware flow
394 control (RTS/CTS), and interrupt-driven receives. Note that, because of the
395 peculiarities of the 6551 chip, together with the use of the NMI, transmits
396 are not interrupt driven; and, the transceiver blocks if the receiver asserts
397 flow control because of a full buffer.
410 <sect1>Escape code<p>
412 For an Esc, press CTRL and the <tt/[/ key.
415 <sect1>Passing arguments to the program<p>
417 Command-line arguments can be passed to <tt/main()/. Since this is not
418 supported directly by BASIC, the following syntax was chosen:
421 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
425 <item>Arguments are separated by spaces.
426 <item>Arguments may be quoted.
427 <item>Leading and trailing spaces around an argument are ignored. Spaces within
428 a quoted argument are allowed.
429 <item>The first argument passed to <tt/main()/ is the program name.
430 <item>A maximum number of 10 arguments (including the program name) are
435 <sect1>Program return code<p>
437 The program return code (low byte) is passed back to BASIC by use of the
443 The runtime for the C64 uses routines marked as <tt/.INTERRUPTOR/ for
444 interrupt handlers. Such routines must be written as simple machine language
445 subroutines and will be called automatically by the interrupt handler code
446 when they are linked into a program. See the discussion of the <tt/.CONDES/
447 feature in the <url url="ca65.html" name="assembler manual">.
453 This software is provided 'as-is', without any expressed or implied
454 warranty. In no event will the authors be held liable for any damages
455 arising from the use of this software.
457 Permission is granted to anyone to use this software for any purpose,
458 including commercial applications, and to alter it and redistribute it
459 freely, subject to the following restrictions:
462 <item> The origin of this software must not be misrepresented; you must not
463 claim that you wrote the original software. If you use this software
464 in a product, an acknowledgment in the product documentation would be
465 appreciated but is not required.
466 <item> Altered source versions must be plainly marked as such, and must not
467 be misrepresented as being the original software.
468 <item> This notice may not be removed or altered from any source