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>Hardware access<p>
67 The following pseudo variables declared in the <tt/atmos.h/ header file do allow
68 access to hardware located in the address space. Some variables are
69 structures, accessing the struct fields will access the chip registers.
74 Access to the VIA (versatile interface adapter) chip is available via the
75 <tt/VIA/ variable. The structure behind this variable is explained in <tt/_6522.h/.
81 <sect>Loadable drivers<p>
83 <em>Note:</em> Since the Atmos doesn't have working disk I/O
84 (see <ref id="limitations" name="section "Limitations"">), the
85 available drivers cannot be loaded at runtime (so the term "loadable drivers"
86 is somewhat misleading). Instead, the drivers have to be converted using the
87 <htmlurl url="co65.html" name="co65 utility"> and statically linked. While
88 this may seem overhead, it has two advantages:
91 <item>The interface is identical to the one used for other platforms
92 and to the one for the Atmos once it has disk I/O.
93 <item>Once disk I/O is available, existing code can be changed to load drivers
94 at runtime with almost no effort.
99 <sect1>Graphics drivers<p>
103 <tag><tt/atmos-240-200-2.tgi/</tag>
104 This driver was written by Stefan Haubenthal. It features a resolution of
105 240×200 with 2 colors.
110 <sect1>Extended memory drivers<p>
112 No extended memory drivers are currently available for the Atmos.
115 <sect1>Joystick drivers<p>
119 <tag><tt/atmos-pase.joy/</tag>
120 Supports two standard joysticks connected to the P.A.S.E. interface of the Atmos.
126 <sect1>Mouse drivers<p>
128 No mouse drivers are currently available for the Atmos.
131 <sect1>RS232 device drivers<p>
135 <tag><tt/atmos-acia.ser/</tag>
136 Driver for the Telestrat integrated serial controller and the Atmos with a
138 Note that because of the peculiarities of the 6551 chip together with the
139 use of the NMI, transmits are not interrupt driven, and the transceiver
140 blocks if the receiver asserts flow control because of a full buffer.
146 <sect>Limitations<label id="limitations"><p>
150 The existing library for the Atmos doesn't implement C file
151 I/O. There is one hack for the <tt/write()/ routine in
152 place, which will make functions work that write to <tt/stdout/
153 (like <tt/printf()/). However, this function has some shortcomings which
154 won't be fixed, because it's going to be replaced anyway.
156 To be more concrete, this limitation means that you cannot use any of the
157 following functions (and a few others):
174 <sect1>Function keys<p>
176 These are defined to be FUNCT + number key.
178 <sect1>Passing arguments to the program<p>
180 Command line arguments can be passed to <tt/main()/. Since this is not
181 supported by BASIC, the following syntax was chosen:
184 CALL#500:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
188 <item>Arguments are separated by spaces.
189 <item>Arguments may be quoted.
190 <item>Leading and trailing spaces around an argument are ignored. Spaces within
191 a quoted argument are allowed.
192 <item>The first argument passed to <tt/main/ is the program name.
193 <item>A maximum number of 10 arguments (including the program name) are
200 The runtime for the Atmos uses routines marked as <tt/.CONDES/ type 2 for
201 interrupt handlers. Such routines must be written as simple machine language
202 subroutines and will be called automatically by the interrupt handler code
203 when they are linked into a program. See the discussion of the <tt/.CONDES/
204 feature in the <htmlurl url="ca65.html" name="assembler manual">.
208 <sect>Bugs/Feedback<p>
210 If you have problems using the library, if you find any bugs, or if you're
211 doing something interesting with it, I would be glad to hear from you. Feel
212 free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
213 name="uz@cc65.org">).
219 This software is provided 'as-is', without any expressed or implied
220 warranty. In no event will the authors be held liable for any damages
221 arising from the use of this software.
223 Permission is granted to anyone to use this software for any purpose,
224 including commercial applications, and to alter it and redistribute it
225 freely, subject to the following restrictions:
228 <item> The origin of this software must not be misrepresented; you must not
229 claim that you wrote the original software. If you use this software
230 in a product, an acknowledgment in the product documentation would be
231 appreciated but is not required.
232 <item> Altered source versions must be plainly marked as such, and must not
233 be misrepresented as being the original software.
234 <item> This notice may not be removed or altered from any source