1 <!doctype linuxdoc system>
5 <title>Oric Atmos specific information for cc65
6 <author>Ullrich von Bassewitz <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org"><newline>
7 Stefan A. Haubenthal <htmlurl url="mailto:polluks@sdf.lonestar.org" name="polluks@sdf.lonestar.org"><newline>
8 <url url="mailto:greg.king5@verizon.net" name="Greg King">
12 An overview over the Atmos runtime system as it is implemented for the cc65 C
16 <!-- Table of contents -->
19 <!-- Begin the document -->
23 This file contains an overview of the Atmos runtime system as it comes with the
24 cc65 C compiler. It describes the memory layout, Atmos specific header files,
25 available drivers, and any pitfalls specific to that platform.
27 Please note that Atmos specific functions are just mentioned here, they are
28 described in detail in the separate <htmlurl url="funcref.html" name="function
29 reference">. Even functions marked as "platform dependent" may be available on
30 more than one platform. Please see the function reference for more
34 <sect>Binary format<p>
36 The standard binary output format generated by the linker for the Atmos target
37 is a machine language program with a 17 byte tape header including a cc65 tag.
38 The standard load and autostart address is $500.
41 <sect>Memory layout<p>
43 In the standard setup, cc65 generated programs use the memory from
44 $500 to $9800, so nearly 37K of memory (including the stack) is
45 available. ROM calls are possible without further precautions.
51 The C runtime stack is located at $97FF and growing downwards.
54 The C heap is located at the end of the program and grows towards the C
61 <sect>Platform specific header files<p>
63 Programs containing Atmos specific code may use the <tt/atmos.h/ header file.
66 <sect1>Atmos specific functions<p>
68 The functions listed below are special for the Atmos. See the <htmlurl
69 url="funcref.html" name="function reference"> for declaration and usage.
77 <sect1>Hardware access<p>
79 The following pseudo variables declared in the <tt/atmos.h/ header file do allow
80 access to hardware located in the address space. Some variables are
81 structures, accessing the struct fields will access the chip registers.
86 Access to the VIA (versatile interface adapter) chip is available via the
87 <tt/VIA/ variable. The structure behind this variable is explained in <tt/_6522.h/.
93 <sect>Loadable drivers<p>
95 <em>Note:</em> Since the Atmos doesn't have working disk I/O
96 (see <ref id="limitations" name="section "Limitations"">), the
97 available drivers cannot be loaded at runtime (so the term "loadable drivers"
98 is somewhat misleading). Instead, the drivers have to be statically linked. While
99 this may seem overhead, it has two advantages:
102 <item>The interface is identical to the one used for other platforms
103 and to the one for the Atmos once it has disk I/O.
104 <item>Once disk I/O is available, existing code can be changed to load drivers
105 at runtime with almost no effort.
108 The names in the parentheses denote the symbols to be used for static linking of the drivers.
111 <sect1>Graphics drivers<p>
115 <tag><tt/atmos-228-200-3.tgi (atmos_228_200_3)/</tag>
116 This driver was written by Greg King and Stefan Haubenthal.
117 It features a resolution of 228×200 with a palette of two colors that
118 can be chosen from the Atmos's eight colors. The driver supports a third
119 palette-"color" that actually "flips" the pixel (it becomes the other color)
120 that is on the screen under the graphics cursor.
122 <tag><tt/atmos-240-200-2.tgi (atmos_240_200_2)/</tag>
123 This driver was written by Stefan Haubenthal and Greg King.
124 It features a resolution of 240×200 with black and white colors.
125 It is the default graphics driver for the Atmos.
130 <sect1>Extended memory drivers<p>
132 No extended memory drivers are currently available for the Atmos.
135 <sect1>Joystick drivers<p>
139 <tag><tt/atmos-pase.joy (atmos_pase)/</tag>
140 Supports two standard joysticks connected to the P.A.S.E. interface of the Atmos.
145 <sect1>Mouse drivers<p>
147 No mouse drivers are currently available for the Atmos.
150 <sect1>RS232 device drivers<p>
154 <tag><tt/atmos-acia.ser (atmos_acia)/</tag>
155 Driver for the Telestrat integrated serial controller and the Atmos with a
157 Note that because of the peculiarities of the 6551 chip together with the
158 use of the NMI, transmits are not interrupt driven, and the transceiver
159 blocks if the receiver asserts flow control because of a full buffer.
165 <sect>Limitations<label id="limitations"><p>
169 The existing library for the Atmos doesn't implement C file
170 I/O. There is one hack for the <tt/write()/ routine in
171 place, which will make functions work that write to <tt/stdout/
172 (like <tt/printf()/). However, this function has some shortcomings which
173 won't be fixed, because it's going to be replaced anyway.
175 To be more concrete, this limitation means that you cannot use any of the
176 following functions (and a few others):
193 <sect1>Function keys<p>
195 These are defined to be FUNCT + number key.
197 <sect1>Passing arguments to the program<p>
199 Command line arguments can be passed to <tt/main()/. Since this is not
200 supported by BASIC, the following syntax was chosen:
203 CALL#500:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
207 <item>Arguments are separated by spaces.
208 <item>Arguments may be quoted.
209 <item>Leading and trailing spaces around an argument are ignored. Spaces within
210 a quoted argument are allowed.
211 <item>The first argument passed to <tt/main/ is the program name.
212 <item>A maximum number of 10 arguments (including the program name) are
219 The runtime for the Atmos uses routines marked as <tt/.INTERRUPTOR/ for
220 interrupt handlers. Such routines must be written as simple machine language
221 subroutines and will be called automatically by the interrupt handler code
222 when they are linked into a program. See the discussion of the <tt/.CONDES/
223 feature in the <htmlurl url="ca65.html" name="assembler manual">.
227 <sect>Bugs/Feedback<p>
229 If you have problems using the library, if you find any bugs, or if you're
230 doing something interesting with it, I would be glad to hear from you. Feel
231 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
232 name="uz@cc65.org">).
238 This software is provided 'as-is', without any expressed or implied
239 warranty. In no event will the authors be held liable for any damages
240 arising from the use of this software.
242 Permission is granted to anyone to use this software for any purpose,
243 including commercial applications, and to alter it and redistribute it
244 freely, subject to the following restrictions:
247 <item> The origin of this software must not be misrepresented; you must not
248 claim that you wrote the original software. If you use this software
249 in a product, an acknowledgment in the product documentation would be
250 appreciated but is not required.
251 <item> Altered source versions must be plainly marked as such, and must not
252 be misrepresented as being the original software.
253 <item> This notice may not be removed or altered from any source