1 <!doctype linuxdoc system>
5 <title>Commodore PET 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 PET 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 PET runtime system as it comes with the
23 cc65 C compiler. It describes the memory layout, PET specific header files,
24 available drivers, and any pitfalls specific to that platform.
26 Please note that PET 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 PET 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 and BASIC ROM enabled, which gives a usable memory range of
46 $0400 - $7FFF (32KB machine).
47 All ROM entry points may be called directly without additional code.
53 The text screen is located at $8000.
56 The C runtime stack is located at $7FFF 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 PET specific code may use the <tt/pet.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/pet.h/ and declares several functions
71 common to all CBM platforms.
74 <sect1>PET specific functions<p>
76 There are currently no special PET 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/pet.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.
120 <tag><tt/PIA1, PIA2/</tag>
121 Access to the two PIA (peripheral interface adapter) chips is available via
122 the <tt/PIA1/ and <tt/PIA2/ variables. The structure behind these variables
123 is explained in <tt/_pia.h/.
126 The <tt/VIA/ structure allows access to the VIA (versatile interface
127 adapter). See the <tt/_6522.h/ header file located in the include
128 directory for the declaration of the structure.
134 <sect>Loadable drivers<p>
136 The names in the parentheses denote the symbols to be used for static linking of the drivers.
139 <sect1>Graphics drivers<p>
141 No graphics drivers are currently available for the PET.
144 <sect1>Extended memory drivers<p>
146 No extended memory drivers are currently available for the PET.
149 <sect1>Joystick drivers<p>
153 <tag><tt/pet-ptvjoy.joy (pet_ptvjoy_joy)/</tag>
154 Driver for the Protovision 4-player adapter contributed by Groepaz. See
155 <htmlurl url="http://www.protovision-online.de/hardw/hardwstart.htm"
156 name="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and
157 building instructions. Up to two joysticks are supported.
159 <tag><tt/pet-stdjoy.joy (pet_stdjoy_joy)/</tag>
160 Driver for the standard PET userport joystick.
165 <sect1>Mouse drivers<p>
167 No mouse drivers are currently available for the PET.
170 <sect1>RS232 device drivers<p>
172 No serial drivers are currently available for the PET.
182 <sect1>Passing arguments to the program<p>
184 Command line arguments can be passed to <tt/main()/. Since this is not
185 supported by BASIC, the following syntax was chosen:
188 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
192 <item>Arguments are separated by spaces.
193 <item>Arguments may be quoted.
194 <item>Leading and trailing spaces around an argument are ignored. Spaces within
195 a quoted argument are allowed.
196 <item>The first argument passed to <tt/main/ is the program name.
197 <item>A maximum number of 10 arguments (including the program name) are
202 <sect1>Program return code<p>
204 The program return code (low byte) is passed back to BASIC by use of the
210 The runtime for the PET uses routines marked as <tt/.INTERRUPTOR/ for
211 interrupt handlers. Such routines must be written as simple machine language
212 subroutines and will be called automatically by the interrupt handler code
213 when they are linked into a program. See the discussion of the <tt/.CONDES/
214 feature in the <htmlurl url="ca65.html" name="assembler manual">.
217 <sect1>Using extended memory<p>
219 The extended memory at $9000 of the CBM 8x96 may be added to the heap by using
223 /* Check for the existence of RAM */
224 if (PEEK(0x9000) == POKE(0x9000, PEEK(0x9000)+1)) {
225 /* Add it to the heap */
226 _heapadd ((void *) 0x9000, 0x2000);
233 This software is provided 'as-is', without any expressed or implied
234 warranty. In no event will the authors be held liable for any damages
235 arising from the use of this software.
237 Permission is granted to anyone to use this software for any purpose,
238 including commercial applications, and to alter it and redistribute it
239 freely, subject to the following restrictions:
242 <item> The origin of this software must not be misrepresented; you must not
243 claim that you wrote the original software. If you use this software
244 in a product, an acknowledgment in the product documentation would be
245 appreciated but is not required.
246 <item> Altered source versions must be plainly marked as such, and must not
247 be misrepresented as being the original software.
248 <item> This notice may not be removed or altered from any source