1 <!doctype linuxdoc system>
5 <title>Commodore 128 specific information for cc65
6 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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 <htmlurl 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 $CFFF 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 <htmlurl
83 url="funcref.html" name="function reference"> for declaration and usage.
93 <sect1>CBM specific functions<p>
95 Some functions are available for all (or at least most) of the Commodore
96 machines. See the <htmlurl url="funcref.html" name="function reference"> for
97 declaration and usage.
125 <sect1>Hardware access<p>
127 The following pseudo variables declared in the <tt/c128.h/ header file do
128 allow access to hardware located in the address space. Some variables are
129 structures, accessing the struct fields will access the chip registers.
134 The <tt/VIC/ structure allows access to the VIC II (the graphics
135 controller). See the <tt/_vic2.h/ header file located in the include
136 directory for the declaration of the structure.
139 The <tt/SID/ structure allows access to the SID (the sound interface
140 device). See the <tt/_sid.h/ header file located in the include directory
141 for the declaration of the structure.
144 The <tt/VDC/ structure allows access to the VDC (the video display
145 controller). See the <tt/_vdc.h/ header file located in the include
146 directory for the declaration of the structure.
148 <tag><tt/CIA1, CIA2/</tag>
149 Access to the two CIA (complex interface adapter) chips is available via
150 the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
151 is explained in <tt/_6526.h/.
153 <tag><tt/COLOR_RAM/</tag>
154 A character array that mirrors the color RAM of the C64 at $D800.
160 <sect>Loadable drivers<p>
162 <sect1>Graphics drivers<p>
164 Note: The graphics drivers for the VDC are incompatible with the extended
165 memory drivers using the VDC memory!
168 <tag><tt/c128-vdc.tgi/</tag>
169 This driver was written by Maciej Witkowiak. It uses the 80 column display
170 and features a resolution of 640*200 with two colors and an adjustable
171 palette (that means that the two colors can be chosen out of the 16 VDC
174 <tag><tt/c128-vdc2.tgi/</tag>
175 This driver was written by Maciej Witkowiak. This driver uses the 80 column
176 display and features a resolution of 640*480 with two colors and an
177 adjustable palette (that means that the two colors can be chosen out of the
178 16 VDC colors). The driver requires 64KB VDC RAM.
181 Note: The colors are translated from definitions in headers to correct VDC values
182 so please use definitions or VIC color numbers only. Colors <tt/GRAY3/ and <tt/BROWN/ are
183 missing on VDC and are translated to the two colors missing from VIC palette.
185 <sect1>Extended memory drivers<p>
189 <tag><tt/c128-georam.emd/</tag>
190 A driver for the GeoRam cartridge. The driver will always assume 2048 pages
191 of 256 bytes each. There are no checks, so if your program knows better,
194 <tag><tt/c128-ram.emd/</tag>
195 An extended memory driver for the RAM in page 1. The common memory area is
196 excluded, so this driver supports 251 pages of 256 bytes each.
198 <tag><tt/c128-ram2.emd/</tag>
200 An extended memory driver for the RAM in pages 1-3. The common memory area
201 is excluded, so this driver supports up to 731 pages of 256 bytes each. The
202 driver can be used as a full replacement for <tt/c128-ram.emd/, because RAM
203 in pages 2+3 is autodetected, but it's larger and there are not many
204 machines with RAM in banks 2+3, so it has been made a separate driver. The
205 additional code was contributed by Marco van den Heuvel.
207 <tag><tt/c128-ramcart.emd/</tag>
208 A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
209 Will test the hardware for the available RAM.
211 <tag><tt/c128-reu.emd/</tag>
212 A driver for the CBM REUs. The driver will determine from the connected REU
213 if it supports 128KB of RAM or more. In the latter case, 256KB are assumed,
214 but since there are no range checks, the application can use more memory if
215 it has better knowledge about the hardware than the driver.
217 <tag><tt/c128-vdc.emd/</tag>
218 A driver for the VDC memory of the C128 written and contributed by Maciej
219 Witkowiak. Autodetects the amount of memory available (16 or 64K) and offers
220 64 or 256 pages of 256 bytes each. Note: This driver is incompatible with
221 any of the graphics drivers using the VDC!
226 <sect1>Joystick drivers<p>
230 <tag><tt/c128-ptvjoy.joy/</tag>
231 Driver for the Protovision 4-player adapter originally written by Groepaz
232 for the C64 and converted for the C128 by me. See <htmlurl
233 url="http://www.protovision-online.de/hardw/hardwstart.htm"
234 name="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and
235 building instructions. Up to four joysticks are supported.
237 <tag><tt/c128-stdjoy.joy/</tag>
238 Supports up to two joysticks connected to the standard joysticks port of
245 <sect1>Mouse drivers<p>
249 <tag><tt/c128-1351.mou/</tag>
250 Supports a standard mouse connected to port #0 of the C128.
252 <tag><tt/c128-joy.mou/</tag>
253 Supports a mouse emulated by a standard joystick e.g. 1350 mouse in port
256 <tag><tt/c128-pot.mou/</tag>
257 Supports a potentiometer device e.g. Koala Pad connected to port #1 of
263 <sect1>RS232 device drivers<p>
267 <tag><tt/c128-swlink.ser/</tag>
268 Driver for the SwiftLink cartridge. Supports up to 38400 baud, hardware flow
269 control (RTS/CTS) and interrupt driven receives. Note that because of the
270 peculiarities of the 6551 chip together with the use of the NMI, transmits
271 are not interrupt driven, and the transceiver blocks if the receiver asserts
272 flow control because of a full buffer.
274 The driver uses the RS232 variables and buffers of the kernal (buffers at
275 $C00 and $D00).
287 <sect1>Passing arguments to the program<p>
289 Command line arguments can be passed to <tt/main()/. Since this is not
290 supported by BASIC, the following syntax was chosen:
293 RUN:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
297 <item>Arguments are separated by spaces.
298 <item>Arguments may be quoted.
299 <item>Leading and trailing spaces around an argument are ignored. Spaces within
300 a quoted argument are allowed.
301 <item>The first argument passed to <tt/main/ is the program name.
302 <item>A maximum number of 10 arguments (including the program name) are
307 <sect1>Program return code<p>
309 The program return code (low byte) is passed back to BASIC by use of the
315 The runtime for the C128 uses routines marked as <tt/.CONDES/ type 2 for
316 interrupt handlers. Such routines must be written as simple machine language
317 subroutines and will be called automatically by the interrupt handler code
318 when they are linked into a program. See the discussion of the <tt/.CONDES/
319 feature in the <htmlurl url="ca65.html" name="assembler manual">.
323 <sect>Bugs/Feedback<p>
325 If you have problems using the library, if you find any bugs, or if you're
326 doing something interesting with it, I would be glad to hear from you. Feel
327 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
328 name="uz@cc65.org">).
334 This software is provided 'as-is', without any expressed or implied
335 warranty. In no event will the authors be held liable for any damages
336 arising from the use of this software.
338 Permission is granted to anyone to use this software for any purpose,
339 including commercial applications, and to alter it and redistribute it
340 freely, subject to the following restrictions:
343 <item> The origin of this software must not be misrepresented; you must not
344 claim that you wrote the original software. If you use this software
345 in a product, an acknowledgment in the product documentation would be
346 appreciated but is not required.
347 <item> Altered source versions must be plainly marked as such, and must not
348 be misrepresented as being the original software.
349 <item> This notice may not be removed or altered from any source