1 <!doctype linuxdoc system>
5 <title>Oric Atmos-specific information for cc65
7 <url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
8 <url url="mailto:polluks@sdf.lonestar.org" name="Stefan A. Haubenthal">,<newline>
9 <url url="mailto:greg.king5@verizon.net" name="Greg King">
13 An overview over the Atmos runtime system as it is implemented for the cc65 C
17 <!-- Table of contents -->
20 <!-- Begin the document -->
24 This file contains an overview of the Atmos runtime system as it comes with the
25 cc65 C compiler. It describes the memory layout, Atmos-specific header files,
26 available drivers, and any pitfalls specific to that platform.
28 Please note that Atmos-specific functions are just mentioned here, they are
29 described in detail in the separate <url url="funcref.html" name="function
30 reference">. Even functions marked as "platform dependent" may be available on
31 more than one platform. Please see the function reference for more
35 <sect>Binary format<p>
37 The standard binary output format generated by the linker for the Atmos target
38 is a machine language program with a 17 byte tape header including a cc65 tag.
39 The standard load and autostart address is $500.
42 <sect>Memory layout<p>
44 In the standard setup, cc65 generated programs use the memory from
45 $500 to $9800, so nearly 37K of memory (including the stack) is
46 available. ROM calls are possible without further precautions.
52 The C runtime stack is located at $97FF and growing downwards.
55 The C heap is located at the end of the program and grows towards the C
62 <sect>Platform-specific header files<p>
64 Programs containing Atmos-specific code may use the <tt/atmos.h/ header file.
67 <sect1>Atmos-specific functions<p>
69 The functions listed below are special for the Atmos. See the <url
70 url="funcref.html" name="function reference"> for declaration and usage.
84 <sect1>Hardware access<p>
86 The following pseudo variables declared in the <tt/atmos.h/ header file do allow
87 access to hardware located in the address space. Some variables are
88 structures; accessing the struct fields will access the chip registers.
93 Access to the VIA (versatile interface adapter) chip is available via the
94 <tt/VIA/ variable. The structure behind this variable is explained in <tt/_6522.h/.
100 <sect>Loadable drivers<p>
102 <em>Note:</em> Since the Atmos doesn't have working disk I/O
103 (see <ref id="limitations" name="section "Limitations"">), the
104 available drivers cannot be loaded at runtime (so the term "loadable drivers"
105 is somewhat misleading). Instead, the drivers have to be statically linked. While
106 this may seem overhead, it has two advantages:
109 <item>The interface is identical to the one used for other platforms
110 and to the one for the Atmos once it has disk I/O.
111 <item>Once disk I/O is available, existing code can be changed to load drivers
112 at runtime with almost no effort.
115 The names in the parentheses denote the symbols to be used for static linking of the drivers.
118 <sect1>Graphics drivers<p>
120 The default drivers, <tt/tgi_stddrv (tgi_static_stddrv)/, point to <tt/atmos-240-200-2.tgi (atmos_240_200_2_tgi)/.
124 <tag><tt/atmos-228-200-3.tgi (atmos_228_200_3_tgi)/</tag>
125 This driver was written by Greg King and Stefan Haubenthal.
126 It features a resolution of 228×200 with a palette of two colors that
127 can be chosen from the Atmos's eight colors. The driver supports a third
128 palette-"color" that actually "flips" the pixel (it becomes the other color)
129 that is on the screen under the graphics cursor.
131 <tag><tt/atmos-240-200-2.tgi (atmos_240_200_2_tgi)/</tag>
132 This driver was written by Stefan Haubenthal and Greg King.
133 It features a resolution of 240×200 with black and white colors.
134 It is the default graphics driver for the Atmos.
139 <sect1>Extended memory drivers<p>
141 No extended memory drivers are currently available for the Atmos.
144 <sect1>Joystick drivers<p>
148 <tag><tt/atmos-pase.joy (atmos_pase_joy)/</tag>
149 Supports two standard joysticks connected to the P.A.S.E. interface of the Atmos.
154 <sect1>Mouse drivers<p>
156 No mouse drivers are currently available for the Atmos.
159 <sect1>RS232 device drivers<p>
163 <tag><tt/atmos-acia.ser (atmos_acia_ser)/</tag>
164 Driver for the Telestrat integrated serial controller and the Atmos with a
166 Note that, because of the peculiarities of the 6551 chip, together with the
167 use of the NMI, transmits are not interrupt driven; and, the transceiver
168 blocks if the receiver asserts flow control because of a full buffer.
174 <sect>Limitations<label id="limitations"><p>
178 The existing library for the Atmos doesn't implement C file
179 I/O. There are hacks for the <tt/read()/ and <tt/write()/ routines in
180 place, which will make functions work that read from and write to <tt/stdout/
181 (like <tt/printf()/). However, those functions have some shortcomings which
182 won't be fixed, because they're going to be replaced anyway.
184 To be more concrete, the limitation means that you cannot use any of the
185 following functions (and a few others):
203 <sect1>Function keys<p>
205 These are defined to be FUNCT + number key.
208 <sect1>Passing arguments to the program<p>
210 Command-line arguments can be passed to <tt/main()/. Since that is not
211 supported directly by BASIC, the following syntax was chosen:
214 CALL#500:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
218 <item>Arguments are separated by spaces.
219 <item>Arguments may be quoted.
220 <item>Leading and trailing spaces around an argument are ignored. Spaces within
221 a quoted argument are allowed.
222 <item>The first argument passed to <tt/main()/ is the program name.
223 <item>A maximum number of 10 arguments (including the program name) are
230 The runtime for the Atmos uses routines marked as <tt/.INTERRUPTOR/ for
231 interrupt handlers. Such routines must be written as simple machine language
232 subroutines and will be called automatically by the interrupt handler code
233 when they are linked into a program. See the discussion of the <tt/.CONDES/
234 feature in the <url url="ca65.html" name="assembler manual">.
240 This software is provided 'as-is', without any expressed or implied
241 warranty. In no event will the authors be held liable for any damages
242 arising from the use of this software.
244 Permission is granted to anyone to use this software for any purpose,
245 including commercial applications, and to alter it and redistribute it
246 freely, subject to the following restrictions:
249 <item> The origin of this software must not be misrepresented; you must not
250 claim that you wrote the original software. If you use this software
251 in a product, an acknowledgment in the product documentation would be
252 appreciated but is not required.
253 <item> Altered source versions must be plainly marked as such, and must not
254 be misrepresented as being the original software.
255 <item> This notice may not be removed or altered from any source