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
36 <sect>Binary format<p>
38 The standard binary output format generated by the linker for the Atmos target
39 is a machine language program with a one-line BASIC stub that jumps to the
40 machine-language part through <tt/CALL/. It has one sacrificial byte attached
41 to the end (a bug in the Oric ROM means that BASIC can put a variable on top
42 of the last byte that was loaded). It has a 24-byte tape header. A file can
43 be CLOADed as a BASIC program, and started by typing <tt/RUN/. The standard
44 load address is $501.
48 <sect>Memory layout<p>
50 In the standard setup, cc65-generated programs use the memory from
51 $0501 to $9800; so, nearly 37K of memory (including the stack) is
52 available. ROM calls are possible without further precautions.
54 If your program needs more memory, and it won't use TGI graphics, then you can
55 use the ld65 command-line option, <tt/-D __GRAB__=1/, when building the
56 program, to include the graphics screen RAM. Then, nearly 44K of memory
57 ($0501 to $B400) is available.
63 The C runtime stack is located at $97FF (or $B3FF), and grows
67 The C heap is located at the end of the program, and grows towards the C
74 <sect>Platform-specific header files<p>
76 Programs containing Atmos-specific code may use the <tt/atmos.h/ header file.
79 <sect1>Atmos-specific functions<p>
81 The functions listed below are special for the Atmos. See the <url
82 url="funcref.html" name="function reference"> for declaration and usage.
96 <sect1>Hardware access<p>
98 The following pseudo variables declared in the <tt/atmos.h/ header file do allow
99 access to hardware located in the address space. Some variables are
100 structures; accessing the struct fields will access the chip registers.
105 Access to the VIA (Versatile Interface Adapter) chip is available via the
106 <tt/VIA/ variable. The structure behind this variable is explained in <tt/_6522.h/.
112 <sect>Loadable drivers<p>
114 <em>Note:</em> Since the Atmos doesn't have working disk I/O
115 (see <ref id="limitations" name="section "Limitations"">), the
116 available drivers cannot be loaded at runtime (so the term "loadable drivers"
117 is somewhat misleading). Instead, the drivers have to be statically linked. While
118 this may seem overhead, it has two advantages:
121 <item>The interface is identical to the one used for other platforms
122 and to the one for the Atmos once it has disk I/O.
123 <item>Once disk I/O is available, existing code can be changed to load drivers
124 at runtime with almost no effort.
127 The names in the parentheses denote the symbols to be used for static linking of the drivers.
130 <sect1>Graphics drivers<p>
132 The default drivers, <tt/tgi_stddrv (tgi_static_stddrv)/,
133 point to <tt/atmos-240-200-2.tgi (atmos_240_200_2_tgi)/.
137 <tag><tt/atmos-228-200-3.tgi (atmos_228_200_3_tgi)/</tag>
138 This driver was written by Greg King and Stefan Haubenthal.
139 It features a resolution of 228×200 with a palette of two colors that
140 can be chosen from the Atmos's eight colors. The driver supports a third
141 palette-"color" that actually "flips" the pixel (it becomes the other color)
142 that is on the screen under the graphics cursor.
144 <tag><tt/atmos-240-200-2.tgi (atmos_240_200_2_tgi)/</tag>
145 This driver was written by Stefan Haubenthal and Greg King.
146 It features a resolution of 240×200 with black and white colors.
147 It is the default graphics driver for the Atmos.
152 <sect1>Extended memory drivers<p>
154 No extended memory drivers are currently available for the Atmos.
157 <sect1>Joystick drivers<p>
161 <tag><tt/atmos-pase.joy (atmos_pase_joy)/</tag>
162 Supports two standard joysticks connected to the P.A.S.E. interface of the Atmos.
167 <sect1>Mouse drivers<p>
169 No mouse drivers are currently available for the Atmos.
172 <sect1>RS232 device drivers<p>
176 <tag><tt/atmos-acia.ser (atmos_acia_ser)/</tag>
177 Driver for the Telestrat integrated serial controller and the Atmos with a
179 Note that, because of the peculiarities of the 6551 chip, together with the
180 use of the NMI, transmits are not interrupt driven; and, the transceiver
181 blocks if the receiver asserts flow control because of a full buffer.
187 <sect>Limitations<label id="limitations"><p>
191 The existing library for the Atmos doesn't implement C file I/O. There are
192 hacks for the <tt/read()/ and <tt/write()/ routines in place, which will make
193 functions work that read from <tt/stdin/ and write to <tt/stdout/ and
194 <tt/stderr/ (such as <tt/printf()/). However, those functions have some
195 shortcomings which won't be fixed, because they're going to be replaced
198 To be more concrete, that limitation means that you cannot use any of the
199 following functions (and a few others):
217 <sect1>Function keys<p>
219 They are defined to be FUNCT + a number key.
222 <sect1>Capitals lock<p>
224 The keyboard's "CAPS Lock" mode is turned off while the program is running.
225 The previous mode (usually, CAPS Lock turned on [because Oric BASIC keywords
226 must be UPPER-case]) is restored when the program stops.
229 <sect1>Passing arguments to the program<p>
231 Command-line arguments can be passed to <tt/main()/. Since that is not
232 supported directly by BASIC, the following syntax was chosen:
235 RUN:REM arg1 " ARG2 IS QUOTED" ARG3 "" ARG5
239 <item>You must turn <tt/CAPS/ lock off (tap CTRL-T) when you want to type
240 lower-case arguments (but, <tt/RUN/ and <tt/REM/ must be UPPER-case).
241 <item>Arguments are separated by spaces.
242 <item>Arguments may be quoted.
243 <item>Leading and trailing spaces around an argument are ignored. Spaces within
244 a quoted argument are allowed.
245 <item>The first argument passed to <tt/main()/ is the program name.
246 <item>A maximum number of 10 arguments (including the program name) are
251 <sect1>Automatic starting<p>
253 Usually, a cc65-built program just will sit quietly in memory, after it is
254 CLOADed. It waits for you to start it (by typing BASIC's <tt/RUN/ command).
255 But, if you want to create a program that will start running immediately after
256 it is loaded, then you can use the linker command-line option
257 <tt/-D __AUTORUN__=$C7/.
262 The runtime for the Atmos uses routines marked as <tt/.INTERRUPTOR/ for
263 interrupt handlers. Such routines must be written as simple machine language
264 subroutines and will be called automatically by the interrupt handler code
265 when they are linked into a program. See the discussion of the <tt/.CONDES/
266 feature in the <url url="ca65.html" name="assembler manual">.
272 This software is provided 'as-is', without any expressed or implied
273 warranty. In no event will the authors be held liable for any damages
274 arising from the use of this software.
276 Permission is granted to anyone to use this software for any purpose,
277 including commercial applications, and to alter it and redistribute it
278 freely, subject to the following restrictions:
281 <item> The origin of this software must not be misrepresented; you must not
282 claim that you wrote the original software. If you use this software
283 in a product, an acknowledgment in the product documentation would be
284 appreciated but is not required.
285 <item> Altered source versions must be plainly marked as such, and must not
286 be misrepresented as being the original software.
287 <item> This notice may not be removed or altered from any source