1 <!doctype linuxdoc system>
5 <title>Apple ][ specific information for cc65
6 <author><url url="mailto:ol.sc@web.de" name="Oliver Schmidt">
10 An overview over the Apple ][ runtime system as it is
11 implemented for the cc65 C compiler.
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 This file contains an overview of the Apple ][ runtime system
22 as it comes with the cc65 C compiler. It describes the memory layout,
23 Apple ][ specific header files, available drivers, and any
24 pitfalls specific to that platform.
26 Please note that Apple ][ specific functions are just mentioned
27 here, they are described in detail in the separate <url url="funcref.html"
28 name="function reference">. Even functions marked as "platform dependent" may
29 be available on more than one platform. Please see the function reference for
34 <sect>Binary format<p>
36 The standard binary file format generated by the linker for the
37 Apple ][ target is a binary program with a 4 byte DOS 3.3 header
38 containing the load address and load length. The default load address is
41 <bf/AppleCommander 1.3.5/ or later (available at <url
42 url="http://applecommander.sourceforge.net/">) includes the option <tt/-cc65/
43 that allows to put binary files with a DOS 3.3 header onto disk images
44 containing DOS 3.3 as well as ProDOS 8.
46 For ProDOS 8 system programs the load address is fixed to $2000 so there
47 is no need for a header. Thus the linker configuration
48 <ref id="apple-sys-cfg" name="apple2-system.cfg"> for those programs
49 omits the DOS 3.3 header. The right AppleCommander option to put system files
50 without a header on a ProDOS 8 disk image is <tt/-p/.
53 <sect>Memory layout<p>
55 In the standard setup, cc65 generated programs use the memory from
56 $803 to $95FF, so 35.5 KB of RAM are available.
63 The C runtime stack is located at HIMEM and grows downwards, regardless of
64 how your linker config file is setup.
67 The C heap is located at the end of the program and grows towards the C
72 While running <tt/main()/ the Language Card bank 2 is enabled for read access.
73 However while running module constructors/destructors the Language Card is disabled.
75 Enabling the Language Card allows to use it as additional memory for cc65
76 generated code. However code is never automatically placed there. Rather code
77 needs to be explicitly placed in the Language Card either per file by compiling
78 with <tt/--code-name LC/ or per function by enclosing in <tt/#pragma code-name
79 (push, "LC")/ and <tt/#pragma code-name (pop)/. In either case the cc65 runtime
80 system takes care of actually moving the code into the Language Card.
82 The amount of memory available in the Language Card for generated code depends
83 on the <ref id="link-configs" name="linker configuration"> parameters. There are
84 several usefull settings:
88 <tag>LC address: $D400, LC size: $C00</tag>
89 For plain vanilla ProDOS 8 which doesn't actually use the Language Card bank 2
90 memory from $D400 to $DFFF. This is the default setting.
92 <tag>LC address: $D000, LC size: $1000</tag>
93 For ProDOS 8 together with the function <tt/rebootafterexit()/. If a program
94 doesn't quit to the ProDOS 8 dispatcher but rather reboots the machine after
95 exit then a plain vanilla ProDOS 8 doesn't make use of the Language Card bank
98 <tag>LC address: $D000, LC size: $3000</tag>
99 For plain vanilla DOS 3.3 which doesn't make use of the Language Card at all.
105 <sect>Linker configurations<label id="link-configs"><p>
107 The ld65 linker comes with a default config file for the Apple ][,
108 which is used via <tt/-t apple2/.
109 The apple2 package comes with additional secondary linker config files, which
110 are used via <tt/-t apple2 -C <configfile>/.
113 <sect1>default config file (<tt/apple2.cfg/)<label id="apple-def-cfg"><p>
115 Default configuration for a binary program.
121 <tag><tt/STARTADDRESS:/ Program start address</tag>
122 Default: $803. Use <tt/-S <addr>/ to set a different start address.
124 <tag><tt/__EXEHDR__:/ Executable file header</tag>
125 Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
128 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
129 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
132 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
133 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
134 highest usable address.
136 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
137 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
140 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
141 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
147 <sect1><tt/apple2-system.cfg/<label id="apple-sys-cfg"><p>
149 Configuration for a system program running on ProDOS 8 and using the memory from
150 $2000 to $BEFF.
156 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
157 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
160 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
161 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
164 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
165 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
171 <sect1><tt/apple2-overlay.cfg/<p>
173 Configuration for overlay programs with the up to nine overlays. The overlay files
174 don't include the DOS 3.3 header. See <tt>samples/overlaydemo.c</tt> for more
175 information on overlays.
181 <tag><tt/STARTADDRESS:/ Program start address</tag>
182 Default: $803. Use <tt/-S <addr>/ to set a different start address.
184 <tag><tt/__EXEHDR__:/ Executable file header</tag>
185 Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
188 <tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
189 Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
192 <tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
193 Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
194 highest usable address.
196 <tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
197 Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
200 <tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
201 Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
204 <tag><tt/__OVERLAYSIZE__:/ Size of code in the overlays</tag>
205 Default: $1000. Use <tt/-D __OVERLAYSIZE__=<size>/ to set a different
211 <sect1><tt/apple2-asm.cfg/<p>
213 Configuration for a assembler programs which don't need a special setup.
219 <tag><tt/STARTADDRESS:/ Program start address</tag>
220 Default: $803. Use <tt/-S <addr>/ to set a different start address.
222 <tag><tt/__EXEHDR__:/ Executable file header</tag>
223 Default: No header. Use <tt/-u __EXEHDR__ apple2.lib/ to add a DOS 3.3 header
224 (address and length).
230 <sect>ProDOS 8 system programs<p>
232 ProDOS 8 system programs are always loaded to the start address $2000.
233 For cc65 programs this means that the 6 KB from $800 to $2000 are
234 by default unused. There are however several options to make use of that memory
238 <sect1>LOADER.SYSTEM<p>
240 The easiest (and for really large programs in fact the only) way to have a cc65
241 program use the memory from $800 to $2000 is to link it as binary
242 (as opposed to system) program using the default linker configuration
243 <ref id="apple-def-cfg" name="apple2.cfg"> with <tt/__HIMEM__/ set to $BF00
244 and load it with the LOADER.SYSTEM utility. The program then works like a system
245 program (i.e. quits to the ProDOS dispatcher).
247 Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the
248 program to load under name <program>.SYSTEM as a system program. For
249 example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/.
254 If the cc65 program can be successfully linked as system program using the linker
255 configuration <ref id="apple-sys-cfg" name="apple2-system.cfg">, but
256 uses the heap either explicitly or implicitly (i.e. by loading a driver) then
257 the memory from $800 to $2000 can be added to the heap by calling
258 <tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/.
261 <sect1>ProDOS 8 I/O buffers<p>
263 ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default
264 these buffers are allocated by the cc65 runtime system on the heap using
265 <tt/posix_memalign()/. While this is generally the best solution it means quite
266 some overhead for (especially rather small) cc65 programs which do open files
267 but don't make use of the heap otherwise.
269 The apple2 package comes with the alternative ProDOS 8 I/O buffer allocation
270 module <tt/apple2-iobuf-0800.o/ which uses the memory between $800 and
271 the program start address for the 1 KB I/O buffers. For system programs (with
272 start address $2000) this results in up to 6 I/O buffers and thus up to 6
273 concurrently open files.
275 While using <tt/_heapadd()/ as described in the section above together with the
276 default I/O buffer allocation basically yields the same placement of I/O buffers
277 in memory the primary benefit of <tt/apple2-iobuf-0800.o/ is a reduction in code
278 size - and thus program file size - of more than 1400 bytes.
280 Using <tt/apple2-iobuf-0800.o/ is as simple as placing it on the linker command
284 cl65 -t apple2 -C apple2-system.cfg myprog.c apple2-iobuf-0800.o
289 <sect>Platform specific header files<p>
291 Programs containing Apple ][ specific code may use the
292 <tt/apple2.h/ header file.
295 <sect1>Apple ][ specific functions<p>
297 The functions listed below are special for the Apple ][. See
298 the <url url="funcref.html" name="function reference"> for declaration and
306 <item>rebootafterexit
307 <item>ser_apple2_slot
312 <sect1>Hardware access<p>
314 There's currently no support for direct hardware access. This does not mean
315 you cannot do it, it just means that there's no help.
319 <sect>Loadable drivers<p>
321 The names in the parentheses denote the symbols to be used for static linking of the drivers.
324 <sect1>Graphics drivers<p>
328 <tag><tt/a2.lo.tgi (a2_lo_tgi)/</tag>
329 This driver features a resolution of 40×48 with 16 colors.
331 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
332 function clears the corresponding area at the bottom of the screen.
334 <tag><tt/a2.hi.tgi (a2_hi_tgi)/</tag>
335 This driver features a resolution of 280×192 with 8 colors and two
336 hires pages. Note that programs using this driver will have to be linked
337 with <tt/-S $4000/ to reserve the first hires page or with <tt/-S $6000/
338 to reserve both hires pages.
340 The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
341 function doesn't clear the corresponding area at the bottom of the screen.
343 In memory constrained situations the memory from $803 to $1FFF
344 can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/
345 at the beginning of <tt/main()/. Doing so is beneficial even if the program
346 doesn't use the the heap explicitly because loading the driver (and in fact
347 already opening the driver file) uses the heap implicitly.
352 <sect1>Extended memory drivers<p>
356 <tag><tt/a2.auxmem.emd (a2_auxmem_emd)/</tag>
357 Gives access to 47.5 KB RAM (190 pages of 256 bytes each) on an Extended
360 Note that this driver doesn't check for the actual existence of the memory
361 and that it doesn't check for ProDOS 8 RAM disk content!
366 <sect1>Joystick drivers<p>
370 <tag><tt/a2.stdjoy.joy (a2_stdjoy_joy)/</tag>
371 Supports up to two standard analog joysticks connected to the game port of
372 the Apple ][.
377 <sect1>Mouse drivers<p>
381 <tag><tt/a2.stdmou.mou (a2_stdmou_mou)/</tag>
382 Driver for the AppleMouse II Card. Searches all Apple II slots
383 for an AppleMouse II Card compatible firmware. The default bounding
384 box is [0..279,0..191].
386 Programs using this driver will have to be linked with <tt/-S $4000/
387 to reserve the first hires page if they are intended to run on an
388 Apple ][ (in contrast to an Apple //e) because the
389 AppleMouse II Card firmware writes to the hires page when initializing
392 Note that the Apple ][ default mouse callbacks support text
398 <sect1>RS232 device drivers<p>
402 <tag><tt/a2.ssc.ser (a2_ssc_ser)/</tag>
403 Driver for the Apple II Super Serial Card. Supports up to 19200 baud,
404 hardware flow control (RTS/CTS) and interrupt driven receives. Note
405 that because of the peculiarities of the 6551 chip transmits are not
406 interrupt driven, and the transceiver blocks if the receiver asserts
407 flow control because of a full buffer.
409 The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to
410 <tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/
411 succeeds for all Apple II slots, but <tt/ser_open()/ fails with
412 <tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.
423 Although the standard binaries generated by the linker for the Apple ][
424 generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
425 BASIC.SYSTEM) there are some limitations for DOS 3.3:
429 <tag>Disk File I/O</tag>
430 There's no disk file I/O support. Any attempt to use it yields an error with
431 <tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
432 are in general not functional as they depend on disk file I/O. Therefore the statically
433 linked drivers have to be used instead.
436 There's no <tt/interruptor/ support. Any attempt to use it yields the message
437 'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that
438 <tt/a2.stdmou.mou/ and <tt/a2.ssc.ser/ are not functional as they depend on
444 <sect1>Direct console I/O<p>
449 The Apple ][ has no color text mode. Therefore the functions textcolor(),
450 bgcolor() and bordercolor() have no effect.
459 <sect1>Passing arguments to the program<p>
461 Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
462 supported by BASIC, the following syntax was chosen:
465 ]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
469 <item>Arguments are separated by spaces.
470 <item>Arguments may be quoted.
471 <item>Leading and trailing spaces around an argument are ignored. Spaces within
472 a quoted argument are allowed.
473 <item>The first argument passed to <tt/main/ is the program name.
474 <item>A maximum number of 10 arguments (including the program name) are
481 The runtime for the Apple ][ uses routines marked as
482 <tt/.INTERRUPTOR/ for ProDOS 8 interrupt handlers. Such routines must be
483 written as simple machine language subroutines and will be called
484 automatically by the interrupt handler code when they are linked into a
485 program. See the discussion of the <tt/.CONDES/ feature in the <url
486 url="ca65.html" name="assembler manual">.
494 The function <url url="dio.html#s1" name="dio_open()"> has the single
495 parameter <tt/device/ to identify the device to be opened. Therefore an
496 Apple II slot and drive pair is mapped to that <tt/device/ according
500 device = slot + (drive - 1) * 8
503 so that for example slot 6 drive 2 is mapped to <tt/device/ 14.
506 The function <url url="dio.html#s3" name="dio_query_sectcount()"> returns
507 the correct sector count for all ProDOS 8 disks. However for any non-ProDOS 8
508 disk it simply always returns 280 (which is only correct for a 140 KB disk).
509 This condition is indicated by the <tt/_oserror/ value 82.
517 This software is provided 'as-is', without any expressed or implied
518 warranty. In no event will the authors be held liable for any damages
519 arising from the use of this software.
521 Permission is granted to anyone to use this software for any purpose,
522 including commercial applications, and to alter it and redistribute it
523 freely, subject to the following restrictions:
526 <item> The origin of this software must not be misrepresented; you must not
527 claim that you wrote the original software. If you use this software
528 in a product, an acknowledgment in the product documentation would be
529 appreciated but is not required.
530 <item> Altered source versions must be plainly marked as such, and must not
531 be misrepresented as being the original software.
532 <item> This notice may not be removed or altered from any source