1 <!doctype linuxdoc system>
5 <title>Commodore 610 specific information for cc65
6 <author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
10 An overview over the Commodore 610 runtime system as it is implemented for the
14 <!-- Table of contents -->
17 <!-- Begin the document -->
21 This file contains an overview of the CBM 610 runtime system as it comes with
22 the cc65 C compiler. It describes the memory layout, CBM 610 specific header
23 files, available drivers, and any pitfalls specific to that platform.
25 Please note that CBM 610 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
31 In addition to the Commodore 610 (named B40 in the U.S.), several other
32 machines are supported by this cc65 target, since they have identical
33 hardware: The Commodore 620 and 630 (more memory, additional coprocessor
34 card), and the Commodore 710, 720 and 730 (same hardware in another case with
39 <sect>Binary format<p>
41 The standard binary output format generated by the linker for the CBM610
42 target is a machine language program with a short BASIC stub. This means that
43 a program can be loaded as BASIC program and started with RUN. It is of course
44 possible to change this behaviour by using a modified startup file and linker
48 <sect>Memory layout<p>
50 cc65 generated programs for the Commodore 610 run in bank 1, the memory bank
51 reserved for BASIC programs. Since there are no ROMs in this memory bank, the
52 program has almost full 64K for its own. A disadvantage is that kernal
53 subroutines cannot be called (at least not in a fast and effective manner), so
54 the runtime has replace kernal functionality.
56 The default memory configuration for the CBM 610 allocates all memory between
57 $0002 and $FFF0 in bank 1 for the compiled program. Some space
58 in low memory is lost, because a separate hardware stack is set up in page 1,
59 and the kernal replacement functions need some more memory locations. A few
60 more bytes are lost in high memory, because the runtime sets up a CBM
61 compatible jump table at $FF81. The main startup code is located at
62 $0400, so about 63K of the complete bank are actually usable for
65 <bf>Note:</bf> The zero page from $02 to $5F is free to use for
72 The C runtime stack is located at $FF81 and growing downwards.
75 The C heap is located at the end of the program and grows towards the C
81 <sect>Platform specific header files<p>
83 Programs containing CBM 610 specific code may use the <tt/cbm610.h/ or
84 <tt/cbm.h/ header files. Using the later may be an option when writing code
85 for more than one CBM platform, since it includes <tt/cbm610.h/ and declares
86 several functions common to all CBM platforms.
88 Please note that because of <ref id="limitations" name="current limitations">
89 of the runtime library for the platform, several standard C and CBM functions
93 <sect1>CBM 610 specific functions<p>
95 The functions listed below are special for the CBM 610. See the <htmlurl
96 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 <htmlurl url="funcref.html" name="function reference"> for
110 declaration and usage.
113 <sect1>Hardware access<p>
115 The following pseudo variables declared in the <tt/cbm610.h/ header file do
116 allow access to hardware located in the address space. Some variables are
117 structures, accessing the struct fields will access the chip registers.
119 <bf>Note:</bf> All I/O chips are located in the system bank (bank 15) and can
120 therefore not be accessed like on other platforms. Please use one of the
121 <tt/peekbsys/, <tt/peewsys/, <tt/pokebsys/ and <tt/pokewsys/ functions to
122 access the I/O chips. Direct reads and writes to the structures named below
123 will <em>not</em> work!
128 The <tt/CRTC/ structure allows access to the CRTC (the video controller).
129 See the <tt/_6545.h/ header file located in the include directory for the
130 declaration of the structure.
132 <tag><tt/SID/</tag> The <tt/SID/ structure allows access to the SID (the
133 sound interface device). See the <tt/_sid.h/ header file located in the
134 include directory for the declaration of the structure.
137 Access to the ACIA (the RS232 chip) is available via the <tt/ACIA/ variable.
138 See the <tt/_6551.h/ header file located in the include directory for the
139 declaration of the structure.
142 Access to the CIA chip is available via the <tt/CIA/ variable. See the
143 <tt/_6526.h/ header file located in the include directory for the
144 declaration of the structure.
146 <tag><tt/TPI1, TPI2/</tag>
147 The two 6525 triport chips may be accessed by using this variable. See the
148 <tt/_6525.h/ header file located in the include directory for the
149 declaration of the structure.
155 <sect>Loadable drivers<p>
157 <bf>Note:</bf> Since the CBM 610 doesn't have working disk I/O (see <ref
158 id="limitations" name="section "Limitations"">), the available
159 drivers cannot be loaded at runtime (so the term "loadable drivers" is
160 somewhat misleading). Instead, the drivers have to be converted using the
161 <htmlurl url="co65.html" name="co65 utility"> and statically linked. While
162 this may seem overhead, it has two advantages:
165 <item>The interface is identical to the one used for other platforms
166 and to the one for the CBM 610 once it has disk I/O.
167 <item>Once disk I/O is available, existing code can be changed to load drivers
168 at runtime with almost no effort.
172 <sect1>Graphics drivers<p>
174 No graphics drivers are currently available for the Commodore 610 (and since
175 the machine has no graphics capabilities, chances for a graphics driver aren't
179 <sect1>Extended memory drivers<p>
182 <tag><tt/cbm610-ram.emd/</tag>
183 A driver for the RAM in bank 2. Supports up to 255 pages with 256 bytes
188 <sect1>Joystick drivers<p>
190 The Commodore 610 is a business machine and doesn't have joystick ports. There
191 are no drivers for the non existing ports available.
195 <sect1>Mouse drivers<p>
197 Currently no drivers available (in fact, the API for loadable mouse drivers
201 <sect1>RS232 device drivers<p>
203 Currently no RS232 drivers exist for the Commodore 610.
207 <sect>Limitations<label id="limitations"><p>
212 The existing library for the CBM 610 doesn't implement C file I/O. Please note
213 that this includes <tt/printf/! You may use the conio functions for screen I/O.
215 To be more concrete, this limitation means that you cannot use any of the
216 following functions (and a few others):
233 <sect1>Kernal and hardware access<p>
235 Since the program runs in bank 1, and the kernal and all I/O chips are located
236 in bank 15, calling ROM routines or accessing hardware needs special code.
242 <sect1>Passing arguments to the program<p>
244 Command line argument passing is currently not supported for the Commodore
249 <sect>Bugs/Feedback<p>
251 If you have problems using the library, if you find any bugs, or if you're
252 doing something interesting with it, I would be glad to hear from you. Feel
253 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
254 name="uz@cc65.org">).
260 This software is provided 'as-is', without any expressed or implied
261 warranty. In no event will the authors be held liable for any damages
262 arising from the use of this software.
264 Permission is granted to anyone to use this software for any purpose,
265 including commercial applications, and to alter it and redistribute it
266 freely, subject to the following restrictions:
269 <item> The origin of this software must not be misrepresented; you must not
270 claim that you wrote the original software. If you use this software
271 in a product, an acknowledgment in the product documentation would be
272 appreciated but is not required.
273 <item> Altered source versions must be plainly marked as such, and must not
274 be misrepresented as being the original software.
275 <item> This notice may not be removed or altered from any source