1 <!doctype linuxdoc system>
5 <title>Commodore 128-specific information for cc65
6 <author><url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">
10 An overview over the C128 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 C128 runtime system as it comes with the
22 cc65 C compiler. It describes the memory layout, C128-specific header files,
23 available drivers, and any pitfalls specific to that platform.
25 Please note that C128-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
32 <sect>Binary format<p>
34 The standard binary output format generated by the linker for the C128 target
35 is a machine language program with a one line BASIC stub, which calls the
36 machine language part via SYS. This means that a program can be loaded as
37 BASIC program and started with RUN. It is of course possible to change this
38 behaviour by using a modified startup file and linker config.
41 <sect>Memory layout<p>
43 cc65 generated programs with the default setup run with the I/O area and the
44 kernal ROM enabled. Note that this is a non standard memory layout, and that
45 there is no "memory configuration index" for this layout. This means that
46 special care has to be taken when changing the configuration, or calling any
47 code that does this. The memory configuration register at $FF00 should
48 be saved and restored instead of relying on the memory configuration index
49 stored in the zero page.
51 The setup gives a usable memory range of $1C00 - $BFFF. Having
52 just the kernal ROM mapped in means, that kernal entry points may be called
53 directly, but using the BASIC ROM is not possible without additional code.
59 The text screen is located at $400 (as in the standard setup).
62 The C runtime stack is located at $BFFF, and growing downwards.
65 The C heap is located at the end of the program, and grows towards the C
72 <sect>Platform-specific header files<p>
74 Programs containing C128-specific code may use the <tt/c128.h/ or <tt/cbm.h/
75 header files. Using the later may be an option when writing code for more than
76 one CBM platform, since it includes <tt/c128.h/ and declares several functions
77 common to all CBM platforms.
80 <sect1>C128-specific functions<p>
82 The functions listed below are special for the C128. See the <url
83 url="funcref.html" name="function reference"> for declaration and usage.
91 <sect1>C128-specific accelerator functions<p>
93 The functions listed below are accelerator functions for the C128. See the <url
94 url="funcref.html" name="function reference"> for declaration and usage.
106 <sect1>CBM-specific functions<p>
108 Some functions are available for all (or at least most) of the Commodore
109 machines. See the <url url="funcref.html" name="function reference"> for
110 declaration and usage.
140 <sect1>CBM specific CPU functions<p>
142 Some CPU related functions are available for some of the Commodore
143 machines. See the <url url="funcref.html" name="function reference"> for
144 declaration and usage.
153 <sect1>Hardware access<p>
155 The following pseudo variables declared in the <tt/c128.h/ header file do
156 allow access to hardware located in the address space. Some variables are
157 structures, accessing the struct fields will access the chip registers.
162 The <tt/VIC/ structure allows access to the VIC II (the graphics
163 controller). See the <tt/_vic2.h/ header file located in the include
164 directory for the declaration of the structure.
167 The <tt/SID/ structure allows access to the SID (the sound interface
168 device). See the <tt/_sid.h/ header file located in the include directory
169 for the declaration of the structure.
172 The <tt/VDC/ structure allows access to the VDC (the video display
173 controller). See the <tt/_vdc.h/ header file located in the include
174 directory for the declaration of the structure.
176 <tag><tt/CIA1, CIA2/</tag>
177 Access to the two CIA (complex interface adapter) chips is available via
178 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
179 is explained in <tt/_6526.h/.
181 <tag><tt/COLOR_RAM/</tag>
182 A character array that mirrors the color RAM of the C128 at $D800.
188 <sect>Loadable drivers<p>
190 The names in the parentheses denote the symbols to be used for static linking of the drivers.
193 <sect1>Graphics drivers<p>
195 The default drivers, <tt/tgi_stddrv (tgi_static_stddrv)/, point to <tt/c128-vdc.tgi (c128_vdc_tgi)/.
197 Note: The graphics drivers for the VDC are incompatible with the extended
198 memory drivers using the VDC memory!
201 <tag><tt/c128-vdc.tgi (c128_vdc_tgi)/</tag>
202 This driver was written by Maciej Witkowiak. It uses the 80-column display,
203 and features a resolution of 640×200 with two colors and an adjustable
204 palette (that means that the two colors can be chosen out of the 16 VDC
207 <tag><tt/c128-vdc2.tgi (c128_vdc2_tgi)/</tag>
208 This driver was written by Maciej Witkowiak. This driver uses the 80-column
209 display, and features a resolution of 640×480 with two colors and an
210 adjustable palette (that means that the two colors can be chosen out of the
211 16 VDC colors). The driver requires 64KB VDC RAM.
214 Note: The colors are translated from definitions in headers to correct VDC values;
215 so, please use definitions or VIC color numbers only. Colors <tt/GRAY3/ and <tt/BROWN/ are
216 missing on VDC, and are translated to the two colors missing from the VIC palette.
219 <tag><tt/c128-hi.tgi (c128_hi_tgi)/</tag>
220 This driver features a resolution of 320×200 with two colors and an
221 adjustable palette (that means that the two colors can be chosen out of a
222 palette of the 16 VIC colors). Unlike BASIC 7.0 this driver put its graphics
223 data into the RAM behind the ROMs.
227 <sect1>Extended memory drivers<p>
231 <tag><tt/c128-efnram.emd (c128_efnram_emd)/</tag>
232 Extended memory driver for the C128 External Function RAM.
233 Written and contributed by Marco van den Heuvel.
235 <tag><tt/c128-georam.emd (c128_georam_emd)/</tag>
236 A driver for the GeoRam cartridge. The driver will always assume 2048 pages
237 of 256 bytes each. There are no checks, so if your program knows better,
240 <tag><tt/c128-ifnram.emd (c128_ifnram_emd)/</tag>
241 Extended memory driver for the C128 Internal Function RAM.
242 Written and contributed by Marco van den Heuvel.
244 <tag><tt/c128-ram.emd (c128_ram_emd)/</tag>
245 An extended memory driver for the RAM in page 1. The common memory area is
246 excluded, so this driver supports 251 pages of 256 bytes each.
248 <tag><tt/c128-ram2.emd (c128_ram2_emd)/</tag>
249 An extended memory driver for the RAM in pages 1-3. The common memory area
250 is excluded, so this driver supports up to 731 pages of 256 bytes each. The
251 driver can be used as a full replacement for <tt/c128-ram.emd/, because RAM
252 in pages 2+3 is autodetected, but it's larger and there are not many
253 machines with RAM in banks 2+3, so it has been made a separate driver. The
254 additional code was contributed by Marco van den Heuvel.
256 <tag><tt/c128-ramcart.emd (c128_ramcart_emd)/</tag>
257 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
258 Will test the hardware for the available RAM.
260 <tag><tt/c128-reu.emd (c128_reu_emd)/</tag>
261 A driver for the CBM REUs. The driver will test the connected REU to find
262 out how much RAM is present.
264 <tag><tt/c128-vdc.emd (c128_vdc_emd)/</tag>
265 A driver for the VDC memory of the C128, written and contributed by Maciej
266 Witkowiak. Autodetects the amount of memory available (16 or 64K), and offers
267 64 or 256 pages of 256 bytes each. Note: This driver is incompatible with
268 any of the graphics drivers using the VDC!
273 <sect1>Joystick drivers<p>
275 The default drivers, <tt/joy_stddrv (joy_static_stddrv)/, point to <tt/c128-stdjoy.joy (c128_stdjoy_joy)/.
279 <tag><tt/c128-ptvjoy.joy (c128_ptvjoy_joy)/</tag>
280 Driver for the Protovision 4-player adapter originally written by Groepaz
281 for the C64, and converted for the C128 by Uz. See <url
282 url="http://www.protovision-online.de/hardw/4_player.php?language=en"
283 name="Protovision shop"> for prices and building instructions. Up to four
284 joysticks are supported.
286 <tag><tt/c128-stdjoy.joy (c128_stdjoy_joy)/</tag>
287 Supports up to two joysticks connected to the standard joysticks ports of
294 <sect1>Mouse drivers<p>
296 The default drivers, <tt/mouse_stddrv (mouse_static_stddrv)/, point to <tt/c128-1351.mou (c128_1351_mou)/.
300 <tag><tt/c128-1351.mou (c128_1351_mou)/</tag>
301 Supports a standard mouse connected to port #0 of the C128.
303 <tag><tt/c128-inkwell.mou (c128_inkwell_mou)/</tag>
304 Supports the Inkwell Systems lightpens, connected to port #0 of the
305 C128. It can read both the one-button 170-C and the two-button 184-C pens.
306 (It can read other lightpens and light-guns that send their button signal to
307 the joystick left-button pin or the paddle Y [up/down] pin.) It works on
308 only the 40-column screen.
310 <tag><tt/c128-joy.mou (c128_joy_mou)/</tag>
311 Supports a mouse emulated by a standard joystick, e.g. 1350 mouse, in port
314 <tag><tt/c128-pot.mou (c128_pot_mou)/</tag>
315 Supports a potentiometer device, e.g. Koala Pad, connected to port #1 of
321 <sect1>RS232 device drivers<p>
325 <tag><tt/c128-swlink.ser (c128_swlink_ser)/</tag>
326 Driver for the SwiftLink cartridge. Supports up to 38400 BPS, hardware flow
327 control (RTS/CTS), and interrupt-driven receives. Note that, because of the
328 peculiarities of the 6551 chip, together with the use of the NMI, transmits
329 are not interrupt driven; and, the transceiver blocks if the receiver asserts
330 flow control because of a full buffer.
332 The driver uses the RS232 variables and buffers of the kernal (buffers at
333 $C00 and $D00).
346 <sect1>Passing arguments to the program<p>
348 Command-line arguments can be passed to <tt/main()/. Since this is not
349 supported directly by BASIC, the following syntax was chosen:
352 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
356 <item>Arguments are separated by spaces.
357 <item>Arguments may be quoted.
358 <item>Leading and trailing spaces around an argument are ignored. Spaces within
359 a quoted argument are allowed.
360 <item>The first argument passed to <tt/main()/ is the program name.
361 <item>A maximum number of 10 arguments (including the program name) are
366 <sect1>Program return code<p>
368 The program return code (low byte) is passed back to BASIC by use of the
374 The runtime for the C128 uses routines marked as <tt/.INTERRUPTOR/ for
375 interrupt handlers. Such routines must be written as simple machine language
376 subroutines and will be called automatically by the interrupt handler code
377 when they are linked into a program. See the discussion of the <tt/.CONDES/
378 feature in the <url url="ca65.html" name="assembler manual">.
384 This software is provided 'as-is', without any expressed or implied
385 warranty. In no event will the authors be held liable for any damages
386 arising from the use of this software.
388 Permission is granted to anyone to use this software for any purpose,
389 including commercial applications, and to alter it and redistribute it
390 freely, subject to the following restrictions:
393 <item> The origin of this software must not be misrepresented; you must not
394 claim that you wrote the original software. If you use this software
395 in a product, an acknowledgment in the product documentation would be
396 appreciated but is not required.
397 <item> Altered source versions must be plainly marked as such, and must not
398 be misrepresented as being the original software.
399 <item> This notice may not be removed or altered from any source