1 <!doctype linuxdoc system>
5 <title>Commodore VIC20 (aka VC20 aka VIC1001) specific information for cc65
7 <url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
8 <url url="mailto:polluks@sdf.lonestar.org" name="Stefan A. Haubenthal">
12 An overview over the VIC20 runtime system as it is implemented for the cc65 C
16 <!-- Table of contents -->
19 <!-- Begin the document -->
23 This file contains an overview of the VIC20 runtime system as it comes with the
24 cc65 C compiler. It describes the memory layout, VIC20-specific header files,
25 available drivers, and any pitfalls specific to that platform.
27 Please note that VIC20-specific functions are just mentioned here, they are
28 described in detail in the separate <url url="funcref.html" name="function
29 reference">. Even functions marked as "platform dependent" may be available on
30 more than one platform. Please see the function reference for more
34 <sect>Binary format<p>
36 The standard binary output format generated by the linker for the VIC20 target
37 is a machine language program with a one line BASIC stub, which calls the
38 machine language part via SYS. This means that a program can be loaded as
39 BASIC program and started with RUN. It is of course possible to change this
40 behaviour by using a modified startup file and linker config.
43 <sect>Memory layout<p>
45 cc65 generated programs with the default setup run with unexpanded memory
46 (RAM at $A000 - $BFFF may be used for the heap),
47 which gives a usable memory range of $1000 - $1DFF.
48 All ROM entry points may be called directly without additional code.
54 The text screen is located at $1E00 (as in the standard setup).
57 The C runtime stack is located at $1DFF 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 VIC20-specific code may use the <tt/vic20.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/vic20.h/ and declares several functions
72 common to all CBM platforms.
75 <sect1>VIC20-specific functions<p>
77 There are currently no special VIC20 functions.
81 <sect1>CBM-specific functions<p>
83 Some functions are available for all (or at least most) of the Commodore
84 machines. See the <url url="funcref.html" name="function reference"> for
85 declaration and usage.
114 <sect1>Hardware access<p>
116 The following pseudo variables declared in the <tt/vic20.h/ header file do allow
117 access to hardware located in the address space. Some variables are
118 structures, accessing the struct fields will access the chip registers.
123 The <tt/VIC/ structure allows access to the VIC (the graphics
124 controller). See the <tt/_vic.h/ header file located in the include
125 directory for the declaration of the structure.
127 <tag><tt/VIA1, VIA2/</tag>
128 Access to the two VIA (versatile interface adapter) chips is available via
129 the <tt/VIA1/ and <tt/VIA2/ variables. The structure behind these variables
130 is explained in <tt/_6522.h/.
132 <tag><tt/COLOR_RAM/</tag>
133 A character array that mirrors the color RAM of the VIC20 at $9600.
139 <sect>Loadable drivers<p>
141 The names in the parentheses denote the symbols to be used for static linking of the drivers.
144 <sect1>Graphics drivers<p>
146 No graphics drivers are currently available for the VIC20.
149 <sect1>Extended memory drivers<p>
153 <tag><tt/vic20-rama.emd (vic20_rama_emd)/</tag>
154 A driver for any RAM at $A000-$BFFF. Supports 32 256 byte pages.
155 Written and contributed by Marco van den Heuvel.
157 <tag><tt/vic20-georam.emd (vic20_georam_emd)/</tag>
158 A driver for the Berkeley Softworks GeoRam cartridge connected by means of
159 the MasC=erade c64 cartridge adapter. The driver will determine the
160 available RAM from the connected cartridge. It supports 64KB
166 <sect1>Joystick drivers<p>
168 The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/vic20-stdjoy.joy (vic20_stdjoy_joy)/.
172 <tag><tt/vic20-stdjoy.joy (vic20_stdjoy_joy)/</tag>
173 Supports one standard joystick connected to the joysticks port of the VIC20.
175 <tag><tt/vic20-ptvjoy.joy (vic20_ptvjoy_joy)/</tag>
176 Driver for the Protovision 4-player adapter contributed by Groepaz. See
177 <url url="https://www.protovision.games/hardw/4_player.php"
178 name="the Protovision shop"> for prices and building instructions. Up to three
179 joysticks are supported.
184 <sect1>Mouse drivers<p>
186 No mouse drivers are currently available for the VIC20.
189 <sect1>RS232 device drivers<p>
191 No VIC1011 drivers are currently available for the VIC20.
198 <sect1>Escape code<p>
200 The CTRL key cannot be used to type most control characters,
201 entering an Esc is not possible.
208 <sect1>Passing arguments to the program<p>
210 Command-line arguments can be passed to <tt/main()/. Since that is not
211 supported directly by BASIC, the following syntax was chosen:
214 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
218 <item>Arguments are separated by spaces.
219 <item>Arguments may be quoted.
220 <item>Leading and trailing spaces around an argument are ignored. Spaces within
221 a quoted argument are allowed.
222 <item>The first argument passed to <tt/main()/ is the program name.
223 <item>A maximum number of 10 arguments (including the program name) are
228 <sect1>Program return code<p>
230 The program return code (low byte) is passed back to BASIC by use of the
234 <sect1>Using extended memory<p>
236 BLK5 memory may be added to the heap by using the following code:
239 /* Check for the existence of RAM */
240 if (PEEK(0xA000) == POKE(0xA000, PEEK(0xA000)+1)) {
241 /* Add it to the heap */
242 _heapadd ((void *) 0xA000, 0x2000);
249 The runtime for the VIC20 uses routines marked as <tt/.INTERRUPTOR/ for
250 interrupt handlers. Such routines must be written as simple machine language
251 subroutines and will be called automatically by the interrupt handler code
252 when they are linked into a program. See the discussion of the <tt/.CONDES/
253 feature in the <url url="ca65.html" name="assembler manual">.
259 This software is provided 'as-is', without any expressed or implied
260 warranty. In no event will the authors be held liable for any damages
261 arising from the use of this software.
263 Permission is granted to anyone to use this software for any purpose,
264 including commercial applications, and to alter it and redistribute it
265 freely, subject to the following restrictions:
268 <item> The origin of this software must not be misrepresented; you must not
269 claim that you wrote the original software. If you use this software
270 in a product, an acknowledgment in the product documentation would be
271 appreciated but is not required.
272 <item> Altered source versions must be plainly marked as such, and must not
273 be misrepresented as being the original software.
274 <item> This notice may not be removed or altered from any source