1 <!doctype linuxdoc system>
4 <title>Commodore 64-specific information for cc65
5 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz"><newline>
6 <url url="mailto:greg.king5@verizon.net" name="Greg King">
9 An overview over the C64 runtime system as it is implemented for the cc65 C
13 <!-- Table of contents -->
16 <!-- Begin the document -->
20 This file contains an overview of the C64 runtime system as it comes with the
21 cc65 C compiler. It describes the memory layout, C64-specific header files,
22 available drivers, and any pitfalls specific to that platform.
24 Please note that C64-specific functions are just mentioned here, they are
25 described in detail in the separate <url url="funcref.html" name="function
26 reference">. Even functions marked as "platform dependent" may be available on
27 more than one platform. Please see the function reference for more
31 <sect>Binary format<p>
33 The standard binary output format generated by the linker for the C64 target
34 is a machine language program with a one line BASIC stub, which calls the
35 machine language part via SYS. This means that a program can be loaded as
36 BASIC program and started with RUN. It is of course possible to change this
37 behaviour by using a modified startup file and linker config.
40 <sect>Memory layout<p>
42 cc65 generated programs with the default setup run with the I/O area and the
43 kernal ROM enabled (memory under the kernal may be used for graphics or as
44 extended memory - see the sections about graphics and extended memory
45 drivers). The BASIC ROM is disabled, which gives a usable memory range of
46 $0800 - $CFFF. This means that kernal entry points may be called
47 directly, but using the BASIC ROM is not possible without additional code.
53 The text screen is located at $400 (as in the standard setup).
56 The C runtime stack is located at $CFFF and growing downwards.
59 The C heap is located at the end of the program and grows towards the C
65 <sect>Linker configurations<p>
67 The ld65 linker comes with a default config file for the Commodore 64,
68 which is used via <tt/-t c64/. The
69 c64 package comes with additional secondary linker config files, which are
70 used via <tt/-t c64 -C <configfile>/.
73 <sect1>default config file (<tt/c64.cfg/)<p>
75 The default configuration is tailored to C programs. It supplies the load
76 address and a small BASIC stub that starts the compiled program using a SYS
80 <sect1><tt/c64-asm.cfg/<p>
82 This configuration is made for assembler programmers who don't need a special
83 setup. The default start address is $801. It can be changed with the
84 linker command line option <tt/--start-addr/. All standard segments with the
85 exception of <tt/zeropage/ are written to the output file and a two byte load
88 To use this config file, assemble with <tt/-t c64/ and link with <tt/-C
89 c64-asm.cfg/. The former will make sure that correct character translation is
90 in effect, while the latter supplies the actual config. When using <tt/cl65/,
91 use both command line options.
93 Sample command line for <tt/cl65/:
96 cl65 -o file.prg -t c64 -C c64-asm.cfg source.s
99 To generate code that loads to $C000:
102 cl65 -o file.prg --start-addr $C000 -t c64 -C c64-asm.cfg source.s
105 It is also possible to add a small BASIC header to the program, that uses SYS
106 to jump to the program entry point (which is the start of the code segment).
107 The advantage is that the program can be started using RUN.
109 To generate a program with a BASIC SYS header, use
112 cl65 -o file.prg -u __EXEHDR__ -t c64 -C c64-asm.cfg source.s
115 Please note that in this case a changed start address doesn't make sense,
116 since the program must be loaded to the BASIC start address.
120 <sect1>80 Columns conio driver<p>
122 The C64 package comes with an alternative software driven 80 columns
123 module <tt/c64-soft80.o/ which uses the memory under I/O between $D000
126 In memory constrained situations the memory from $400 to $7FF
127 can be made available to a program by calling <tt/_heapadd ((void *) 0x0400, 0x0400);/
128 at the beginning of <tt/main()/. Doing so is beneficial even if the program
129 doesn't use the the heap explicitly because loading a driver uses the heap implicitly.
131 Using <tt/c64-soft80.o/ is as simple as placing it on the linker command
135 cl65 -t c64 myprog.c c64-soft80.o
138 Note that the soft80 conio driver is incompatible with the
139 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
140 <tt/c64-hi.tgi (c64_hi_tgi)/ graphics driver.
142 <sect2>80 Columns conio driver (monochrome)<p>
144 In an (even more) memory constrained situation, a size optimized version of the
145 software driven 80 columns module may be used, which only supports one common
146 text color for the whole screen.
149 cl65 -t c64 myprog.c c64-soft80mono.o
152 <sect>Platform-specific header files<p>
154 Programs containing C64-specific code may use the <tt/c64.h/ or <tt/cbm.h/
155 header files. Using the later may be an option when writing code for more than
156 one CBM platform, since it includes <tt/c64.h/ and declares several functions
157 common to all CBM platforms.
160 <sect1>C64-specific functions<p>
162 The functions listed below are special for the C64. See the <url
163 url="funcref.html" name="function reference"> for declaration and usage.
170 <sect1>C64-specific accelerator functions<p>
172 The functions listed below are accelerator functions for the C64. See the <url
173 url="funcref.html" name="function reference"> for declaration and usage.
179 <item>detect_chameleon
181 <item>detect_turbomaster
183 <item>get_c64dtv_speed
185 <item>get_chameleon_speed
187 <item>get_turbomaster_speed
189 <item>set_c64dtv_speed
191 <item>set_chameleon_speed
193 <item>set_turbomaster_speed
197 <sect1>CBM-specific functions<p>
199 Some functions are available for all (or at least most) of the Commodore
200 machines. See the <url url="funcref.html" name="function reference"> for
201 declaration and usage.
231 <sect1>Hardware access<p>
233 The following pseudo variables declared in the <tt/c64.h/ header file do allow
234 access to hardware located in the address space. Some variables are
235 structures, accessing the struct fields will access the chip registers.
240 The <tt/VIC/ structure allows access to the VIC II (the graphics
241 controller). See the <tt/_vic2.h/ header file located in the include
242 directory for the declaration of the structure.
245 The <tt/SID/ structure allows access to the SID (the sound interface
246 device). See the <tt/_sid.h/ header file located in the include directory
247 for the declaration of the structure.
249 <tag><tt/CIA1, CIA2/</tag>
250 Access to the two CIA (complex interface adapter) chips is available via
251 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
252 is explained in <tt/_6526.h/.
254 <tag><tt/COLOR_RAM/</tag>
255 A character array that mirrors the color RAM of the C64 at $D800.
261 <sect>Loadable drivers<p>
263 The names in the parentheses denote the symbols to be used for static linking of the drivers.
266 <label id="graphics-drivers">
267 <sect1>Graphics drivers<p>
269 <em>Note:</em> All available graphics drivers for the TGI interface will use
270 the space below the I/O area and Kernal ROM; so, you can have hires graphics in
271 the standard setup without any memory loss or need for a changed configuration.
273 You can use a mouse driver at the same time that you use a TGI driver. But, if
274 you want to see the default mouse pointer on the graphics screen, then you
275 explicitly must link a special object file into your program. It will put the
276 arrow into the "high RAM" area where the bitmaps are put. Its name is
277 "<tt/c64-tgimousedata.o/". Example:
280 cl65 -t c64 -o program-file main-code.c subroutines.s c64-tgimousedata.o
284 <tag><tt/c64-hi.tgi (c64_hi_tgi)/</tag>
285 This driver features a resolution of 320*200 with two colors and an
286 adjustable palette (that means that the two colors can be chosen out of a
287 palette of the 16 C64 colors).
290 Note that the graphics drivers are incompatible with the
291 <tt/c64-ram.emd (c64_ram_emd)/ extended memory driver and the
292 <tt/c64-soft80.o/ software 80-columns conio driver.
295 <sect1>Extended memory drivers<p>
299 <tag><tt/c64-65816.emd (c64_65816_emd)/</tag>
300 Extended memory driver for 65816 (eg SCPU) based extra RAM.
301 Written and contributed by Marco van den Heuvel.
303 <tag><tt/c64-c256k.emd (c64_c256k_emd)/</tag>
304 A driver for the C64 256K memory expansion. This driver offers 768 pages of
305 256 bytes each. Written and contributed by Marco van den Heuvel.
307 <tag><tt/c64-dqbb.emd (c64_dqbb_emd)/</tag>
308 A driver for the Double Quick Brown Box cartridge. This driver offers
309 64 pages of 256 bytes each. Written and contributed by Marco van den Heuvel.
311 <tag><tt/c64-georam.emd (c64_georam_emd)/</tag>
312 A driver for the Berkeley Softworks GeoRam cartridge. The driver will
313 determine the available RAM from the connected cartridge. It supports 64KB
316 <tag><tt/c64-isepic.emd (c64_isepic_emd)/</tag>
317 A driver for the ISEPIC cartridge. This driver offers just 8 pages of 256
318 bytes each. Written and contributed by Marco van den Heuvel.
320 <tag><tt/c64-ram.emd (c64_ram_emd)/</tag>
321 A driver for the hidden RAM below the I/O area and kernal ROM. Supports 47
322 256 byte pages. Please note that this driver is incompatible with any of the
323 graphics drivers, or the soft80 conio driver!
325 <tag><tt/c64-ramcart.emd (c64_ramcart_emd)/</tag>
326 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
327 Will test the hardware for the available RAM.
329 <tag><tt/c64-reu.emd (c64_reu_emd)/</tag>
330 A driver for the CBM REUs. The driver will test the connected REU to find
331 out how much RAM is present.
333 <tag><tt/c64-vdc.emd (c64_vdc_emd)/</tag>
334 A driver for the VDC memory of the C128. Written and contributed by Maciej
335 Witkowiak. Can be used if the program is running in C64 mode of the C128.
336 Autodetects the amount of memory available (16 or 64K) and offers 64 or 256
337 pages of 256 bytes each.
339 <tag><tt/dtv-himem.emd (dtv_himem_emd)/</tag>
340 A driver for the C64 D2TV (the second or PAL version). This driver offers
341 indeed 7680 pages of 256 bytes each.
346 <sect1>Joystick drivers<p>
348 The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/c64-stdjoy.joy (c64_stdjoy_joy)/.
352 <tag><tt/c64-hitjoy.joy (c64_hitjoy_joy)/</tag>
353 Driver for the Digital Excess & Hitmen adapter contributed by Groepaz.
354 See <url url="http://www.digitalexcess.de/downloads/productions.php"> on
355 instructions how to build one. Up to four joysticks are supported.
357 <tag><tt/c64-ptvjoy.joy (c64_ptvjoy_joy)/</tag>
358 Driver for the Protovision 4-player adapter contributed by Groepaz. See
359 <url url="http://www.protovision-online.de/hardw/4_player.php?language=en"
360 name="Protovision shop"> for prices and building instructions. Up to four
361 joysticks are supported.
363 <tag><tt/c64-stdjoy.joy (c64_stdjoy_joy)/</tag>
364 Supports up to two standard joysticks connected to the joysticks port of
367 <tag><tt/c64-numpad.joy (c64_numpad_joy)/</tag>
368 Supports one joystick emulated by the numberpad of the C128 in C64 mode,
369 the firebutton is labeled &dquot;5&dquot; and ENTER.
374 <sect1>Mouse drivers<p>
376 You can use these drivers in text-mode or graphics-mode (TGI) programs. See
377 the description of <ref id="graphics-drivers" name="the graphics drivers">.
379 The default drivers, <tt/mouse_stddrv (mouse_static_stddrv)/, point to <tt/c64-1351.mou (c64_1351_mou)/.
383 <tag><tt/c64-1351.mou (c64_1351_mou)/</tag>
384 Supports a standard mouse connected to port #0 of the C64.
386 <tag><tt/c64-inkwell.mou (c64_inkwell_mou)/</tag>
387 Supports the Inkwell Systems lightpens, connected to port #0 of the C64.
388 It can read both the one-button 170-C and the two-button 184-C pens. (It can
389 read other lightpens and light-guns that send their button signal to the
390 joystick left-button pin or the paddle Y [up/down] pin.)
392 <tag><tt/c64-joy.mou (c64_joy_mou)/</tag>
393 Supports a mouse emulated by a standard joystick, e.g. 1350 mouse, in port
396 <tag><tt/c64-pot.mou (c64_pot_mou)/</tag>
397 Supports a potentiometer device, e.g. Koala Pad, connected to port #1 of
403 <sect1>RS232 device drivers<p>
407 <tag><tt/c64-swlink.ser (c64_swlink_ser)/</tag>
408 Driver for the SwiftLink cartridge. Supports up to 38400 BPS, hardware flow
409 control (RTS/CTS), and interrupt-driven receives. Note that, because of the
410 peculiarities of the 6551 chip, together with the use of the NMI, transmits
411 are not interrupt driven; and, the transceiver blocks if the receiver asserts
412 flow control because of a full buffer.
421 <sect1>Realtime clock<p>
423 The realtime clock functions use the CIA1 TOD clock. As that clock only stores
424 the time but not the date, the date set by <tt/clock_settime()/ is simply stored
425 inside the C library for retrieval in the same program via <tt/clock_gettime()/.
432 <sect1>Escape code<p>
434 For an Esc, press CTRL and the <tt/[/ key.
437 <sect1>Passing arguments to the program<p>
439 Command-line arguments can be passed to <tt/main()/. Since this is not
440 supported directly by BASIC, the following syntax was chosen:
443 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
447 <item>Arguments are separated by spaces.
448 <item>Arguments may be quoted.
449 <item>Leading and trailing spaces around an argument are ignored. Spaces within
450 a quoted argument are allowed.
451 <item>The first argument passed to <tt/main()/ is the program name.
452 <item>A maximum number of 10 arguments (including the program name) are
457 <sect1>Program return code<p>
459 The program return code (low byte) is passed back to BASIC by use of the
465 The runtime for the C64 uses routines marked as <tt/.INTERRUPTOR/ for
466 interrupt handlers. Such routines must be written as simple machine language
467 subroutines and will be called automatically by the interrupt handler code
468 when they are linked into a program. See the discussion of the <tt/.CONDES/
469 feature in the <url url="ca65.html" name="assembler manual">.
475 This software is provided 'as-is', without any expressed or implied
476 warranty. In no event will the authors be held liable for any damages
477 arising from the use of this software.
479 Permission is granted to anyone to use this software for any purpose,
480 including commercial applications, and to alter it and redistribute it
481 freely, subject to the following restrictions:
484 <item> The origin of this software must not be misrepresented; you must not
485 claim that you wrote the original software. If you use this software
486 in a product, an acknowledgment in the product documentation would be
487 appreciated but is not required.
488 <item> Altered source versions must be plainly marked as such, and must not
489 be misrepresented as being the original software.
490 <item> This notice may not be removed or altered from any source