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.
180 <item>get_c64dtv_speed
182 <item>set_c64dtv_speed
187 <sect1>CBM-specific functions<p>
189 Some functions are available for all (or at least most) of the Commodore
190 machines. See the <url url="funcref.html" name="function reference"> for
191 declaration and usage.
219 <sect1>Hardware access<p>
221 The following pseudo variables declared in the <tt/c64.h/ header file do allow
222 access to hardware located in the address space. Some variables are
223 structures, accessing the struct fields will access the chip registers.
228 The <tt/VIC/ structure allows access to the VIC II (the graphics
229 controller). See the <tt/_vic2.h/ header file located in the include
230 directory for the declaration of the structure.
233 The <tt/SID/ structure allows access to the SID (the sound interface
234 device). See the <tt/_sid.h/ header file located in the include directory
235 for the declaration of the structure.
237 <tag><tt/CIA1, CIA2/</tag>
238 Access to the two CIA (complex interface adapter) chips is available via
239 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
240 is explained in <tt/_6526.h/.
242 <tag><tt/COLOR_RAM/</tag>
243 A character array that mirrors the color RAM of the C64 at $D800.
249 <sect>Loadable drivers<p>
251 The names in the parentheses denote the symbols to be used for static linking of the drivers.
254 <label id="graphics-drivers">
255 <sect1>Graphics drivers<p>
257 <em>Note:</em> All available graphics drivers for the TGI interface will use
258 the space below the I/O area and Kernal ROM; so, you can have hires graphics in
259 the standard setup without any memory loss or need for a changed configuration.
261 You can use a mouse driver at the same time that you use a TGI driver. But, if
262 you want to see the default mouse pointer on the graphics screen, then you
263 explicitly must link a special object file into your program. It will put the
264 arrow into the "high RAM" area where the bitmaps are put. Its name is
265 "<tt/c64-tgimousedata.o/". Example:
268 cl65 -t c64 -o program-file main-code.c subroutines.s c64-tgimousedata.o
272 <tag><tt/c64-hi.tgi (c64_hi_tgi)/</tag>
273 This driver features a resolution of 320*200 with two colors and an
274 adjustable palette (that means that the two colors can be chosen out of a
275 palette of the 16 C64 colors).
278 Note that the graphics drivers are incompatible with the
279 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
280 <tt/c64-soft80.o/ software 80-columns conio driver.
283 <sect1>Extended memory drivers<p>
287 <tag><tt/c64-65816.emd (c64_65816_emd)/</tag>
288 Extended memory driver for 65816 (eg SCPU) based extra RAM.
289 Written and contributed by Marco van den Heuvel.
291 <tag><tt/c64-c256k.emd (c64_c256k_emd)/</tag>
292 A driver for the C64 256K memory expansion. This driver offers 768 pages of
293 256 bytes each. Written and contributed by Marco van den Heuvel.
295 <tag><tt/c64-dqbb.emd (c64_dqbb_emd)/</tag>
296 A driver for the Double Quick Brown Box cartridge. This driver offers
297 64 pages of 256 bytes each. Written and contributed by Marco van den Heuvel.
299 <tag><tt/c64-georam.emd (c64_georam_emd)/</tag>
300 A driver for the Berkeley Softworks GeoRam cartridge. The driver will
301 determine the available RAM from the connected cartridge. It supports 64KB
304 <tag><tt/c64-isepic.emd (c64_isepic_emd)/</tag>
305 A driver for the ISEPIC cartridge. This driver offers just 8 pages of 256
306 bytes each. Written and contributed by Marco van den Heuvel.
308 <tag><tt/c64-ram.emd (c64_ram_emd)/</tag>
309 A driver for the hidden RAM below the I/O area and kernal ROM. Supports 48
310 256 byte pages. Please note that this driver is incompatible with any of the
311 graphics drivers, or the soft80 conio driver!
313 <tag><tt/c64-ramcart.emd (c64_ramcart_emd)/</tag>
314 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
315 Will test the hardware for the available RAM.
317 <tag><tt/c64-reu.emd (c64_reu_emd)/</tag>
318 A driver for the CBM REUs. The driver will test the connected REU to find
319 out how much RAM is present.
321 <tag><tt/c64-vdc.emd (c64_vdc_emd)/</tag>
322 A driver for the VDC memory of the C128. Written and contributed by Maciej
323 Witkowiak. Can be used if the program is running in C64 mode of the C128.
324 Autodetects the amount of memory available (16 or 64K) and offers 64 or 256
325 pages of 256 bytes each.
327 <tag><tt/dtv-himem.emd (dtv_himem_emd)/</tag>
328 A driver for the C64 D2TV (the second or PAL version). This driver offers
329 indeed 7680 pages of 256 bytes each.
334 <sect1>Joystick drivers<p>
336 The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/c64-stdjoy.joy (c64_stdjoy_joy)/.
340 <tag><tt/c64-hitjoy.joy (c64_hitjoy_joy)/</tag>
341 Driver for the Digital Excess & Hitmen adapter contributed by Groepaz.
342 See <url url="http://www.digitalexcess.de/downloads/productions.php"> on
343 instructions how to build one. Up to four joysticks are supported.
345 <tag><tt/c64-ptvjoy.joy (c64_ptvjoy_joy)/</tag>
346 Driver for the Protovision 4-player adapter contributed by Groepaz. See
347 <url url="http://www.protovision-online.de/hardw/4_player.php?language=en"
348 name="Protovision shop"> for prices and building instructions. Up to four
349 joysticks are supported.
351 <tag><tt/c64-stdjoy.joy (c64_stdjoy_joy)/</tag>
352 Supports up to two standard joysticks connected to the joysticks port of
355 <tag><tt/c64-numpad.joy (c64_numpad_joy)/</tag>
356 Supports one joystick emulated by the numberpad of the C128 in C64 mode,
357 the firebutton is labeled &dquot;5&dquot; and ENTER.
362 <sect1>Mouse drivers<p>
364 You can use these drivers in text-mode or graphics-mode (TGI) programs. See
365 the description of <ref id="graphics-drivers" name="the graphics drivers">.
367 The default drivers, <tt/mouse_stddrv (mouse_static_stddrv)/, point to <tt/c64-1351.mou (c64_1351_mou)/.
371 <tag><tt/c64-1351.mou (c64_1351_mou)/</tag>
372 Supports a standard mouse connected to port #0 of the C64.
374 <tag><tt/c64-inkwell.mou (c64_inkwell_mou)/</tag>
375 Supports the Inkwell Systems lightpens, connected to port #0 of the C64.
376 It can read both the one-button 170-C and the two-button 184-C pens. (It can
377 read other lightpens and light-guns that send their button signal to the
378 joystick left-button pin or the paddle Y [up/down] pin.)
380 <tag><tt/c64-joy.mou (c64_joy_mou)/</tag>
381 Supports a mouse emulated by a standard joystick, e.g. 1350 mouse, in port
384 <tag><tt/c64-pot.mou (c64_pot_mou)/</tag>
385 Supports a potentiometer device, e.g. Koala Pad, connected to port #1 of
391 <sect1>RS232 device drivers<p>
395 <tag><tt/c64-swlink.ser (c64_swlink_ser)/</tag>
396 Driver for the SwiftLink cartridge. Supports up to 38400 BPS, hardware flow
397 control (RTS/CTS), and interrupt-driven receives. Note that, because of the
398 peculiarities of the 6551 chip, together with the use of the NMI, transmits
399 are not interrupt driven; and, the transceiver blocks if the receiver asserts
400 flow control because of a full buffer.
413 <sect1>Escape code<p>
415 For an Esc, press CTRL and the <tt/[/ key.
418 <sect1>Passing arguments to the program<p>
420 Command-line arguments can be passed to <tt/main()/. Since this is not
421 supported directly by BASIC, the following syntax was chosen:
424 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
428 <item>Arguments are separated by spaces.
429 <item>Arguments may be quoted.
430 <item>Leading and trailing spaces around an argument are ignored. Spaces within
431 a quoted argument are allowed.
432 <item>The first argument passed to <tt/main()/ is the program name.
433 <item>A maximum number of 10 arguments (including the program name) are
438 <sect1>Program return code<p>
440 The program return code (low byte) is passed back to BASIC by use of the
446 The runtime for the C64 uses routines marked as <tt/.INTERRUPTOR/ for
447 interrupt handlers. Such routines must be written as simple machine language
448 subroutines and will be called automatically by the interrupt handler code
449 when they are linked into a program. See the discussion of the <tt/.CONDES/
450 feature in the <url url="ca65.html" name="assembler manual">.
456 This software is provided 'as-is', without any expressed or implied
457 warranty. In no event will the authors be held liable for any damages
458 arising from the use of this software.
460 Permission is granted to anyone to use this software for any purpose,
461 including commercial applications, and to alter it and redistribute it
462 freely, subject to the following restrictions:
465 <item> The origin of this software must not be misrepresented; you must not
466 claim that you wrote the original software. If you use this software
467 in a product, an acknowledgment in the product documentation would be
468 appreciated but is not required.
469 <item> Altered source versions must be plainly marked as such, and must not
470 be misrepresented as being the original software.
471 <item> This notice may not be removed or altered from any source