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5 <title>Commodore Plus/4 specific information for cc65
6 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">
10 An overview over the Plus/4 runtime system as it is implemented for the cc65 C
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 This file contains an overview of the Plus/4 runtime system as it comes with the
22 cc65 C compiler. It describes the memory layout, Plus/4 specific header files,
23 available drivers, and any pitfalls specific to that platform.
25 Please note that Plus/4 specific functions are just mentioned here, they are
26 described in detail in the separate <url url="funcref.html" name="function
27 reference">. Even functions marked as "platform dependent" may be available on
28 more than one platform. Please see the function reference for more
31 Since the Plus/4 and the Commodore 16/116 are almost identical (the latter are
32 missing the 6551 ACIA and do only have 16KB of memory), the <url
33 url="c16.html" name="C16 documentation"> is also worth a look. The difference
34 between both cc65 targets is that the Plus/4 runtime uses banking to support
35 full 64K RAM, while the C16 does not use banking and supports up to 32K RAM.
36 Because banking is not needed, most C16 programs will be somewhat smaller than
37 the same program compiled for the Plus/4. However, programs compiled for the
38 C16 will always run on the Plus/4, while the reverse is not necessarily true.
41 <sect>Binary format<p>
43 The standard binary output format generated by the linker for the Plus/4
44 target is a machine language program with a one line BASIC stub, which calls
45 the machine language part via SYS. This means that a program can be loaded as
46 BASIC program and started with RUN. It is of course possible to change this
47 behaviour by using a modified startup file and linker config.
50 <sect>Memory layout<p>
52 cc65 generated programs with the default setup run with the kernal and basic
53 banked out. This gives a usable memory range of $1000 - $FD00.
54 Having the kernal and basic ROMs banked out means, that no ROM entry points
55 may be called directly from user code.
61 The text screen is located at $C00 (as in the standard setup).
64 The color RAM is located at $800 (standard location).
67 The C runtime stack is located at $FCFF and growing downwards.
70 The C heap is located at the end of the program and grows towards the C
77 <sect>Platform specific header files<p>
79 Programs containing Plus/4 specific code may use the <tt/plus4.h/ or <tt/cbm.h/
80 header files. Using the later may be an option when writing code for more than
81 one CBM platform, since it includes <tt/plus4.h/ and declares several functions
82 common to all CBM platforms.
84 Please note that most of the header file declarations from the <tt/plus4.h/
85 header file are shared between the C16 and Plus/4 configurations. For this
86 reason, most of it is located in a common header file named <tt/cbm264.h/.
90 <sect1>Plus/4 specific functions<p>
92 There are currently no special Plus/4 functions.
95 <sect1>CBM specific functions<p>
97 Some functions are available for all (or at least most) of the Commodore
98 machines. See the <url url="funcref.html" name="function reference"> for
99 declaration and usage.
127 <sect1>CBM specific CPU functions<p>
129 Some CPU related functions are available for some of the Commodore
130 machines. See the <url url="funcref.html" name="function reference"> for
131 declaration and usage.
140 <sect1>Hardware access<p>
142 The following pseudo variables declared in the <tt/plus4.h/ header file do
143 allow access to hardware located in the address space. Some variables are
144 structures, accessing the struct fields will access the chip registers.
149 The <tt/TED/ structure allows access to the TED chip. See the
150 <tt/_ted.h/ header file located in the include directory for the
151 declaration of the structure.
153 <tag><tt/COLOR_RAM/</tag>
154 A character array that mirrors the color RAM of the Plus/4 at $0800.
160 <sect>Loadable drivers<p>
162 The names in the parentheses denote the symbols to be used for static linking of the drivers.
165 <sect1>Graphics drivers<p>
167 No graphics drivers are currently available for the Plus/4.
170 <sect1>Extended memory drivers<p>
172 No extended memory drivers are currently available for the Plus/4.
175 <sect1>Joystick drivers<p>
179 <tag><tt/plus4-stdjoy.joy (plus4_stdjoy_joy)/</tag>
180 Supports up to two joysticks connected to the standard joysticks port of
186 <sect1>Mouse drivers<p>
188 No mouse drivers are currently available for the Plus/4.
191 <sect1>RS232 device drivers<p>
195 <tag><tt/plus4-stdser.ser (plus4_stdser_ser)/</tag>
196 Driver for the 6551 ACIA chip built into the Plus/4. Supports up to 19200
197 baud, hardware flow control (RTS/CTS) and interrupt driven receives. Note
198 that because of the peculiarities of the 6551 chip transmits are not
199 interrupt driven, and the transceiver blocks if the receiver asserts flow
200 control because of a full buffer.
202 You need an adapter to use the builtin port, since the output levels
203 available at the user port don't follow the RS232 standard.
215 <sect1>Passing arguments to the program<p>
217 Command line arguments can be passed to <tt/main()/. Since this is not
218 supported by BASIC, the following syntax was chosen:
221 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
225 <item>Arguments are separated by spaces.
226 <item>Arguments may be quoted.
227 <item>Leading and trailing spaces around an argument are ignored. Spaces within
228 a quoted argument are allowed.
229 <item>The first argument passed to <tt/main/ is the program name.
230 <item>A maximum number of 10 arguments (including the program name) are
236 <sect1>Program return code<p>
238 The program return code (low byte) is passed back to BASIC by use of the
244 The runtime for the Plus/4 uses routines marked as <tt/.INTERRUPTOR/ for
245 interrupt handlers. Such routines must be written as simple machine language
246 subroutines and will be called automatically by the interrupt handler code
247 when they are linked into a program. See the discussion of the <tt/.CONDES/
248 feature in the <url url="ca65.html" name="assembler manual">.
254 This software is provided 'as-is', without any expressed or implied
255 warranty. In no event will the authors be held liable for any damages
256 arising from the use of this software.
258 Permission is granted to anyone to use this software for any purpose,
259 including commercial applications, and to alter it and redistribute it
260 freely, subject to the following restrictions:
263 <item> The origin of this software must not be misrepresented; you must not
264 claim that you wrote the original software. If you use this software
265 in a product, an acknowledgment in the product documentation would be
266 appreciated but is not required.
267 <item> Altered source versions must be plainly marked as such, and must not
268 be misrepresented as being the original software.
269 <item> This notice may not be removed or altered from any source