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 <url 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 <url
69 url="funcref.html" name="function reference"> for declaration and usage.
83 <sect1>Hardware access<p>
85 The following pseudo variables declared in the <tt/atmos.h/ header file do allow
86 access to hardware located in the address space. Some variables are
87 structures; accessing the struct fields will access the chip registers.
92 Access to the VIA (versatile interface adapter) chip is available via the
93 <tt/VIA/ variable. The structure behind this variable is explained in <tt/_6522.h/.
99 <sect>Loadable drivers<p>
101 <em>Note:</em> Since the Atmos doesn't have working disk I/O
102 (see <ref id="limitations" name="section "Limitations"">), the
103 available drivers cannot be loaded at runtime (so the term "loadable drivers"
104 is somewhat misleading). Instead, the drivers have to be statically linked. While
105 this may seem overhead, it has two advantages:
108 <item>The interface is identical to the one used for other platforms
109 and to the one for the Atmos once it has disk I/O.
110 <item>Once disk I/O is available, existing code can be changed to load drivers
111 at runtime with almost no effort.
114 The names in the parentheses denote the symbols to be used for static linking of the drivers.
117 <sect1>Graphics drivers<p>
119 The default drivers, <tt/tgi_stddrv (tgi_static_stddrv)/, point to <tt/atmos-240-200-2.tgi (atmos_240_200_2_tgi)/.
123 <tag><tt/atmos-228-200-3.tgi (atmos_228_200_3_tgi)/</tag>
124 This driver was written by Greg King and Stefan Haubenthal.
125 It features a resolution of 228×200 with a palette of two colors that
126 can be chosen from the Atmos's eight colors. The driver supports a third
127 palette-"color" that actually "flips" the pixel (it becomes the other color)
128 that is on the screen under the graphics cursor.
130 <tag><tt/atmos-240-200-2.tgi (atmos_240_200_2_tgi)/</tag>
131 This driver was written by Stefan Haubenthal and Greg King.
132 It features a resolution of 240×200 with black and white colors.
133 It is the default graphics driver for the Atmos.
138 <sect1>Extended memory drivers<p>
140 No extended memory drivers are currently available for the Atmos.
143 <sect1>Joystick drivers<p>
147 <tag><tt/atmos-pase.joy (atmos_pase_joy)/</tag>
148 Supports two standard joysticks connected to the P.A.S.E. interface of the Atmos.
153 <sect1>Mouse drivers<p>
155 No mouse drivers are currently available for the Atmos.
158 <sect1>RS232 device drivers<p>
162 <tag><tt/atmos-acia.ser (atmos_acia_ser)/</tag>
163 Driver for the Telestrat integrated serial controller and the Atmos with a
165 Note that, because of the peculiarities of the 6551 chip, together with the
166 use of the NMI, transmits are not interrupt driven; and, the transceiver
167 blocks if the receiver asserts flow control because of a full buffer.
173 <sect>Limitations<label id="limitations"><p>
177 The existing library for the Atmos doesn't implement C file
178 I/O. There are hacks for the <tt/read()/ and <tt/write()/ routines in
179 place, which will make functions work that read from and write to <tt/stdout/
180 (like <tt/printf()/). However, those functions have some shortcomings which
181 won't be fixed, because they're going to be replaced anyway.
183 To be more concrete, the limitation means that you cannot use any of the
184 following functions (and a few others):
202 <sect1>Function keys<p>
204 These are defined to be FUNCT + number key.
207 <sect1>Passing arguments to the program<p>
209 Command-line arguments can be passed to <tt/main()/. Since that is not
210 supported directly by BASIC, the following syntax was chosen:
213 CALL#500:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
217 <item>Arguments are separated by spaces.
218 <item>Arguments may be quoted.
219 <item>Leading and trailing spaces around an argument are ignored. Spaces within
220 a quoted argument are allowed.
221 <item>The first argument passed to <tt/main()/ is the program name.
222 <item>A maximum number of 10 arguments (including the program name) are
229 The runtime for the Atmos uses routines marked as <tt/.INTERRUPTOR/ for
230 interrupt handlers. Such routines must be written as simple machine language
231 subroutines and will be called automatically by the interrupt handler code
232 when they are linked into a program. See the discussion of the <tt/.CONDES/
233 feature in the <url url="ca65.html" name="assembler manual">.
239 This software is provided 'as-is', without any expressed or implied
240 warranty. In no event will the authors be held liable for any damages
241 arising from the use of this software.
243 Permission is granted to anyone to use this software for any purpose,
244 including commercial applications, and to alter it and redistribute it
245 freely, subject to the following restrictions:
248 <item> The origin of this software must not be misrepresented; you must not
249 claim that you wrote the original software. If you use this software
250 in a product, an acknowledgment in the product documentation would be
251 appreciated but is not required.
252 <item> Altered source versions must be plainly marked as such, and must not
253 be misrepresented as being the original software.
254 <item> This notice may not be removed or altered from any source