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">
7 Stefan A. Haubenthal, <htmlurl url="mailto:polluks@sdf.lonestar.org" name="polluks@sdf.lonestar.org">
11 An overview over the Atmos runtime system as it is implemented for the cc65 C
15 <!-- Table of contents -->
18 <!-- Begin the document -->
22 This file contains an overview of the Atmos runtime system as it comes with the
23 cc65 C compiler. It describes the memory layout, Atmos specific header files,
24 available drivers, and any pitfalls specific to that platform.
26 Please note that Atmos specific functions are just mentioned here, they are
27 described in detail in the separate <htmlurl url="funcref.html" name="function
28 reference">. Even functions marked as "platform dependent" may be available on
29 more than one platform. Please see the function reference for more
33 <sect>Binary format<p>
35 The standard binary output format generated by the linker for the Atmos target
36 is a machine language program with a 17 byte tape header including a cc65 tag.
37 The standard load and autostart address is $500.
40 <sect>Memory layout<p>
42 In the standard setup, cc65 generated programs use the memory from
43 $500 to $9800, so nearly 37K of memory (including the stack) is
44 available. ROM calls are possible without further precautions.
50 The C runtime stack is located at $97FF and growing downwards.
53 The C heap is located at the end of the program and grows towards the C
60 <sect>Platform specific header files<p>
62 Programs containing Atmos specific code may use the <tt/atmos.h/ header file.
65 <sect1>Atmos specific functions<p>
67 The functions listed below are special for the Atmos. See the <htmlurl
68 url="funcref.html" name="function reference"> for declaration and usage.
76 <sect1>Hardware access<p>
78 The following pseudo variables declared in the <tt/atmos.h/ header file do allow
79 access to hardware located in the address space. Some variables are
80 structures, accessing the struct fields will access the chip registers.
85 Access to the VIA (versatile interface adapter) chip is available via the
86 <tt/VIA/ variable. The structure behind this variable is explained in <tt/_6522.h/.
92 <sect>Loadable drivers<p>
94 <em>Note:</em> Since the Atmos doesn't have working disk I/O
95 (see <ref id="limitations" name="section "Limitations"">), the
96 available drivers cannot be loaded at runtime (so the term "loadable drivers"
97 is somewhat misleading). Instead, the drivers have to be converted using the
98 <htmlurl url="co65.html" name="co65 utility"> and 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.
110 <sect1>Graphics drivers<p>
114 <tag><tt/atmos-240-200-2.tgi/</tag>
115 This driver was written by Stefan Haubenthal. It features a resolution of
116 240×200 with 2 colors.
121 <sect1>Extended memory drivers<p>
123 No extended memory drivers are currently available for the Atmos.
126 <sect1>Joystick drivers<p>
130 <tag><tt/atmos-pase.joy/</tag>
131 Supports two standard joysticks connected to the P.A.S.E. interface of the Atmos.
137 <sect1>Mouse drivers<p>
139 No mouse drivers are currently available for the Atmos.
142 <sect1>RS232 device drivers<p>
146 <tag><tt/atmos-acia.ser/</tag>
147 Driver for the Telestrat integrated serial controller and the Atmos with a
149 Note that because of the peculiarities of the 6551 chip together with the
150 use of the NMI, transmits are not interrupt driven, and the transceiver
151 blocks if the receiver asserts flow control because of a full buffer.
157 <sect>Limitations<label id="limitations"><p>
161 The existing library for the Atmos doesn't implement C file
162 I/O. There is one hack for the <tt/write()/ routine in
163 place, which will make functions work that write to <tt/stdout/
164 (like <tt/printf()/). However, this function has some shortcomings which
165 won't be fixed, because it's going to be replaced anyway.
167 To be more concrete, this limitation means that you cannot use any of the
168 following functions (and a few others):
185 <sect1>Function keys<p>
187 These are defined to be FUNCT + number key.
189 <sect1>Passing arguments to the program<p>
191 Command line arguments can be passed to <tt/main()/. Since this is not
192 supported by BASIC, the following syntax was chosen:
195 CALL#500:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
199 <item>Arguments are separated by spaces.
200 <item>Arguments may be quoted.
201 <item>Leading and trailing spaces around an argument are ignored. Spaces within
202 a quoted argument are allowed.
203 <item>The first argument passed to <tt/main/ is the program name.
204 <item>A maximum number of 10 arguments (including the program name) are
211 The runtime for the Atmos uses routines marked as <tt/.INTERRUPTOR/ for
212 interrupt handlers. Such routines must be written as simple machine language
213 subroutines and will be called automatically by the interrupt handler code
214 when they are linked into a program. See the discussion of the <tt/.CONDES/
215 feature in the <htmlurl url="ca65.html" name="assembler manual">.
219 <sect>Bugs/Feedback<p>
221 If you have problems using the library, if you find any bugs, or if you're
222 doing something interesting with it, I would be glad to hear from you. Feel
223 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
224 name="uz@cc65.org">).
230 This software is provided 'as-is', without any expressed or implied
231 warranty. In no event will the authors be held liable for any damages
232 arising from the use of this software.
234 Permission is granted to anyone to use this software for any purpose,
235 including commercial applications, and to alter it and redistribute it
236 freely, subject to the following restrictions:
239 <item> The origin of this software must not be misrepresented; you must not
240 claim that you wrote the original software. If you use this software
241 in a product, an acknowledgment in the product documentation would be
242 appreciated but is not required.
243 <item> Altered source versions must be plainly marked as such, and must not
244 be misrepresented as being the original software.
245 <item> This notice may not be removed or altered from any source