1 <!doctype linuxdoc system>
5 <title>Commodore VIC20 (aka VC20) specific information for cc65
6 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
7 Stefan A. Haubenthal, <htmlurl url="mailto:polluks@sdf.lonestar.org" name="polluks@sdf.lonestar.org">
11 An overview over the VIC20 runtime system as it is implemented for the cc65 C
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18 <!-- Begin the document -->
22 This file contains an overview of the VIC20 runtime system as it comes with the
23 cc65 C compiler. It describes the memory layout, VIC20 specific header files,
24 available drivers, and any pitfalls specific to that platform.
26 Please note that VIC20 specific functions are just mentioned here, they are
27 described in detail in the separate <htmlurl 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 VIC20 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 unexpanded memory
45 (RAM at $A000 - $BFFF may be used for the heap),
46 which gives a usable memory range of $1000 - $1DFF.
47 All ROM entry points may be called directly without additional code.
53 The text screen is located at $1E00 (as in the standard setup).
56 The C runtime stack is located at $1DFF and growing downwards.
59 The C heap is located at the end of the program and grows towards the C
66 <sect>Platform specific header files<p>
68 Programs containing VIC20 specific code may use the <tt/vic20.h/ or <tt/cbm.h/
69 header files. Using the later may be an option when writing code for more than
70 one CBM platform, since it includes <tt/vic20.h/ and declares several functions
71 common to all CBM platforms.
74 <sect1>VIC20 specific functions<p>
76 There are currently no special VIC20 functions.
80 <sect1>CBM specific functions<p>
82 Some functions are available for all (or at least most) of the Commodore
83 machines. See the <htmlurl url="funcref.html" name="function reference"> for
84 declaration and usage.
112 <sect1>Hardware access<p>
114 The following pseudo variables declared in the <tt/vic20.h/ header file do allow
115 access to hardware located in the address space. Some variables are
116 structures, accessing the struct fields will access the chip registers.
121 The <tt/VIC/ structure allows access to the VIC (the graphics
122 controller). See the <tt/_vic.h/ header file located in the include
123 directory for the declaration of the structure.
125 <tag><tt/VIA1, VIA2/</tag>
126 Access to the two VIA (versatile interface adapter) chips is available via
127 the <tt/VIA1/ and <tt/VIA2/ variables. The structure behind these variables
128 is explained in <tt/_6522.h/.
130 <tag><tt/COLOR_RAM/</tag>
131 A character array that mirrors the color RAM of the VIC20 at $9600.
137 <sect>Loadable drivers<p>
139 The names in the parentheses denote the symbols to be used for static linking of the drivers.
142 <sect1>Graphics drivers<p>
144 No graphics drivers are currently available for the VIC20.
147 <sect1>Extended memory drivers<p>
149 No extended memory drivers are currently available for the VIC20.
152 <sect1>Joystick drivers<p>
156 <tag><tt/vic20-stdjoy.joy (vic20_stdjoy_joy)/</tag>
157 Supports one standard joystick connected to the joysticks port of the VIC20.
159 <tag><tt/vic20-ptvjoy.joy (vic20_ptvjoy_joy)/</tag>
160 Driver for the Protovision 4-player adapter contributed by Groepaz. See
161 <htmlurl url="http://www.protovision-online.de/hardw/hardwstart.htm"
162 name="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and
163 building instructions. Up to three joysticks are supported.
168 <sect1>Mouse drivers<p>
170 No mouse drivers are currently available for the VIC20.
173 <sect1>RS232 device drivers<p>
175 No VIC1011 drivers are currently available for the VIC20.
185 <sect1>Escape code<p>
187 For an Esc press CTRL and [ key.
189 <sect1>Passing arguments to the program<p>
191 Command line arguments can be passed to <tt/main()/. Since this is not
192 supported by BASIC, the following syntax was chosen:
195 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
199 <item>Arguments are separated by spaces.
200 <item>Arguments may be quoted.
201 <item>Leading and trailing spaces around an argument are ignored. Spaces within
202 a quoted argument are allowed.
203 <item>The first argument passed to <tt/main/ is the program name.
204 <item>A maximum number of 10 arguments (including the program name) are
209 <sect1>Program return code<p>
211 The program return code (low byte) is passed back to BASIC by use of the
215 <sect1>Using extended memory<p>
217 The extended memory at $A000 may be added to the heap by using the following
221 /* Check for the existence of RAM */
222 if (PEEK(0xA000) == POKE(0xA000, PEEK(0xA000)+1)) {
223 /* Add it to the heap */
224 _heapadd ((void *) 0xA000, 0x2000);
231 The runtime for the VIC20 uses routines marked as <tt/.INTERRUPTOR/ for
232 interrupt handlers. Such routines must be written as simple machine language
233 subroutines and will be called automatically by the interrupt handler code
234 when they are linked into a program. See the discussion of the <tt/.CONDES/
235 feature in the <htmlurl url="ca65.html" name="assembler manual">.
241 This software is provided 'as-is', without any expressed or implied
242 warranty. In no event will the authors be held liable for any damages
243 arising from the use of this software.
245 Permission is granted to anyone to use this software for any purpose,
246 including commercial applications, and to alter it and redistribute it
247 freely, subject to the following restrictions:
250 <item> The origin of this software must not be misrepresented; you must not
251 claim that you wrote the original software. If you use this software
252 in a product, an acknowledgment in the product documentation would be
253 appreciated but is not required.
254 <item> Altered source versions must be plainly marked as such, and must not
255 be misrepresented as being the original software.
256 <item> This notice may not be removed or altered from any source