Apple ][ specific information for cc65 <author>Oliver Schmidt, <htmlurl url="mailto:ol.sc@web.de" name="ol.sc@web.de"> <date>2009-10-07 <abstract> An overview over the Apple ][ runtime system as it is implemented for the cc65 C compiler. </abstract>  <toc>  <sect>Overview This file contains an overview of the Apple ][ runtime system as it comes with the cc65 C compiler. It describes the memory layout, Apple ][ specific header files, available drivers, and any pitfalls specific to that platform. Please note that Apple ][ specific functions are just mentioned here, they are described in detail in the separate <htmlurl url="funcref.html" name="function reference">. Even functions marked as "platform dependent" may be available on more than one platform. Please see the function reference for more information. <sect>Binary format The standard binary file format generated by the linker for the Apple ][ target is a binary program with a 4 byte DOS 3.3 header containing the load address and load length. The default load address is $803. <bf/AppleCommander 1.3.5/ or later (available at <url url="http://applecommander.sourceforge.net/">) includes the option <tt/-cc65/ that allows to put binary files with a DOS 3.3 header onto disk images containing DOS 3.3 as well as ProDOS 8. For ProDOS 8 system programs the load address is fixed to $2000 so there is no need for a header. Thus the linker configuration <htmlurl url="apple2-4.html#ss4.3" name="apple2-system.cfg"> for those programs omits the DOS 3.3 header. The right AppleCommander option to put system files without a header on a ProDOS 8 disk image is <tt/-p/. <sect>Memory layout In the standard setup, cc65 generated programs use the memory from $803 to $95FF, so 35.5 KB of RAM are available. Special locations: <descrip> <tag/Stack/ The C runtime stack is located at HIMEM and grows downwards, regardless of how your linker config file is setup. <tag/Heap/ The C heap is located at the end of the program and grows towards the C runtime stack. </descrip> While running <tt/main()/ the Language Card bank 2 is enabled for read access. However while running module constructors/destructors the Language Card is disabled. Enabling the Language Card allows to use it as additional memory for cc65 generated code. However code is never automatically placed there. Rather code needs to be explicitly placed in the Language Card either per file by compiling with <tt/--code-name HIGHCODE/ or per function by enclosing in <tt/#pragma code-name (push, "HIGHCODE")/ and <tt/#pragma code-name (pop)/. In either case the cc65 runtime system takes care of actually moving the code into the Language Card. The amount of memory available in the Language Card for generated code depends on the chosen <htmlurl url="apple2-4.html" name="linker configuration">. <sect>Linker configurations The ld65 linker comes with a builtin config file for the Apple ][, which is used via <tt/-t apple2/ (and displayed via <tt/--dump-config apple2/). The apple2 package comes with additional secondary linker config files, which are used via <tt/-C <configfile>/. <sect1>builtin config file Default configuration optimized for a binary program running on ProDOS 8 with BASIC.SYSTEM. A plain vanilla ProDOS 8 doesn't actually use the Language Card bank 2 memory from $D400 to $DFFF. <descrip> <tag><tt/RAM:/ Main memory area</tag> From $803 to $95FF (35.5 KB) <tag><tt/LC:/ Language Card memory area</tag> From $D400 to $DFFF (3 KB) <tag><tt/STARTADDRESS:/ Program start address</tag> Variable (default: $803) <tag><tt/HEADER:/ Binary file header</tag> DOS 3.3 header (address and length) </descrip> <sect1><tt/apple2-dos33.cfg/ Configuration optimized for a binary program running on DOS 3.3. A plain vanilla DOS 3.3 doesn't make use of the Language Card at all. <descrip> <tag><tt/RAM:/ Main memory area</tag> From $803 to $95FF (35.5 KB) <tag><tt/LC:/ Language Card memory area</tag> From $D000 to $FFFF (12 KB) <tag><tt/STARTADDRESS:/ Program start address</tag> Variable (default: $803) <tag><tt/HEADER:/ Binary file header</tag> DOS 3.3 header (address and length) </descrip> <sect1><tt/apple2-system.cfg/ Configuration for a system program running on ProDOS 8. <descrip> <tag><tt/RAM:/ Main memory area</tag> From $2000 to $BEFF (39.75 KB) <tag><tt/LC:/ Language Card memory area</tag> From $D400 to $DFFF (3 KB) <tag><tt/STARTADDRESS:/ Program start address</tag> Fixed ($2000) <tag><tt/HEADER:/ Binary file header</tag> None </descrip> <sect1><tt/apple2-loader.cfg/ Configuration optimized for a binary program running on ProDOS 8 without BASIC.SYSTEM. Intended to be used with <bf/LOADER.SYSTEM - an Apple ][ ProDOS 8 loader for cc65 programs/, which is available in the cc65 User Contributions section. A program loaded by LOADER.SYSTEM works like a ProDOS 8 system program but isn't tied to the start address $2000. Thus with the default start address $800 the main memory area is increased by 6 KB. <descrip> <tag><tt/RAM:/ Main memory area</tag> From $800 to $BEFF (45.75 KB) <tag><tt/LC:/ Language Card memory area</tag> From $D400 to $DFFF (3 KB) <tag><tt/STARTADDRESS:/ Program start address</tag> Variable (default: $800) <tag><tt/HEADER:/ Binary file header</tag> DOS 3.3 header (address and length) </descrip> <sect1><tt/apple2-reboot.cfg/ Configuration optimized for a binary program running on ProDOS 8 without BASIC.SYSTEM. Intended to be used with <bf/LOADER.SYSTEM - an Apple ][ ProDOS 8 loader for cc65 programs/ (see above) together with the function <tt/rebootafterexit()/. If a ProDOS 8 system program doesn't quit to the ProDOS 8 dispatcher but rather reboots the machine after exit then a plain vanilla ProDOS 8 doesn't make use of the Language Card bank 2 at all. This setup makes nearly 50 KB available to a cc65 program - on a 64 KB machine! <descrip> <tag><tt/RAM:/ Main memory area</tag> From $800 to $BEFF (45.75 KB) <tag><tt/LC:/ Language Card memory area</tag> From $D000 to $DFFF (4 KB) <tag><tt/STARTADDRESS:/ Program start address</tag> Variable (default: $800) <tag><tt/HEADER:/ Binary file header</tag> DOS 3.3 header (address and length) </descrip> <sect>ProDOS 8 system programs ProDOS 8 system programs are always loaded to the start address $2000. For cc65 programs this means that the 6 KB from $800 to $2000 are by default unused. There are however several options to make use of that memory range. <sect1>LOADER.SYSTEM The easiest (and for really large programs in fact the only) way to have a cc65 program use the memory from $800 to $2000 is to link it as binary (as opposed to system) program using the linker configuration <htmlurl url="apple2-4.html#ss4.4" name="apple2-loader.cfg"> with start address $800 and load it with <bf/LOADER.SYSTEM - an Apple ][ ProDOS 8 loader for cc65 programs/. The program then works like a system program (i.e. quits to the ProDOS dispatcher). Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the program to load under name <program>.SYSTEM as a system program. For example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/. <sect1>Heap If the cc65 program can be successully linked as system program using the linker configuration <htmlurl url="apple2-4.html#ss4.3" name="apple2-system.cfg"> but uses the heap either explicitly or implicitly (i.e. by loading a driver) then the memory from $800 to $2000 can be added to the heap by calling <tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/. <sect1>ProDOS 8 I/O buffers ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default these buffers are allocated by the cc65 runtime system on the heap using <tt/posix_memalign()/. While this is generally the best solution it means quite some overhead for (especially rather small) cc65 programs which do open files but don't make use of the heap otherwise. The apple2 package comes with the alternative ProDOS 8 I/O buffer allocation module <tt/apple2-iobuf-0800.o/ which uses the memory between $800 and the program start address for the 1 KB I/O buffers. For system programs (with start address $2000) this results in up to 6 I/O buffers and thus up to 6 concurrently open files. While using <tt/_heapadd()/ as described in the section above together with the default I/O buffer allocation basically yields the same placement of I/O buffers in memory the primary benefit of <tt/apple2-iobuf-0800.o/ is a reduction in code size - and thus program file size - of more than 1400 bytes. Using <tt/apple2-iobuf-0800.o/ is as simple as placing it on the linker command line like this: <tscreen><verb> cl65 -t apple2 -C apple2-system.cfg myprog.c apple2-iobuf-0800.o </verb></tscreen> <sect>Platform specific header files Programs containing Apple ][ specific code may use the <tt/apple2.h/ header file. <sect1>Apple ][ specific functions The functions listed below are special for the Apple ][. See the <htmlurl url="funcref.html" name="function reference"> for declaration and usage. <itemize> <item>_dos_type <item>get_ostype <item>rebootafterexit <item>ser_apple2_slot <item>tgi_apple2_mix </itemize> <sect1>Hardware access There's currently no support for direct hardware access. This does not mean you cannot do it, it just means that there's no help. <sect>Loadable drivers <sect1>Graphics drivers <descrip> <tag><tt/a2.lo.tgi/</tag> This driver features a resolution of 40×48 with 16 colors. The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The function clears the corresponding area at the bottom of the screen. <tag><tt/a2.hi.tgi/</tag> This driver features a resolution of 280×192 with 8 colors and two hires pages. Note that programs using this driver will have to be linked with <tt/--start-addr $4000/ to reserve the first hires page or with <tt/--start-addr $6000/ to reserve both hires pages. The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The function doesn't clear the corresponding area at the bottom of the screen. In memory constrained situations the memory from $803 to $1FFF can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/ at the beginning of <tt/main()/. Doing so is beneficial even if the program doesn't use the the heap explicitly because loading the driver (and in fact already opening the driver file) uses the heap implicitly. </descrip> <sect1>Extended memory drivers <descrip> <tag><tt/a2.auxmem.emd/</tag> Gives access to 47,5 KB RAM (190 pages of 256 bytes each) on an Extended 80-Column Text Card. Note that this driver doesn't check for the actual existence of the memory and that it doesn't check for ProDOS 8 RAM disk content! </descrip> <sect1>Joystick drivers <descrip> <tag><tt/a2.stdjoy.joy/</tag> Supports up to two standard analog joysticks connected to the game port of the Apple ][. </descrip> <sect1>Mouse drivers <descrip> <tag><tt/a2.stdmou.mou/</tag> Driver for the AppleMouse II Card. Searches all Apple II slots for an AppleMouse II Card compatible firmware. The default bounding box is [0..279,0..191]. Programs using this driver will have to be linked with <tt/--start-addr $4000/ to reserve the first hires page if they are intended to run on an Apple ][ (in contrast to an Apple //e) because the AppleMouse II Card firmware writes to the hires page when initializing on that machine. Note that the Apple ][ default mouse callbacks support text mode only. </descrip> <sect1>RS232 device drivers <descrip> <tag><tt/a2.ssc.ser/</tag> Driver for the Apple II Super Serial Card. Supports up to 19200 baud, hardware flow control (RTS/CTS) and interrupt driven receives. Note that because of the peculiarities of the 6551 chip transmits are not interrupt driven, and the transceiver blocks if the receiver asserts flow control because of a full buffer. The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to <tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/ succeeds for all Apple II slots, but <tt/ser_open()/ fails with <tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot. </descrip> <sect>Limitations <sect1>DOS 3.3 Although the standard binaries generated by the linker for the Apple ][ generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with BASIC.SYSTEM) there are some limitations for DOS 3.3: <descrip> <tag>Disk File I/O</tag> There's no disk file I/O support. Any attempt to use it yields an error with <tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers are in general not functional as they depend on disk file I/O. However they may be converted to statically linked drivers using the co65 object-file converter. <tag/Interrupts/ There's no <tt/interruptor/ support. Any attempt to use it yields the message 'FAILED TO ALLOC INTERRUPT' on program startup. This implicitly means that <tt/a2.stdmou.mou/ and <tt/a2.ssc.ser/ are not functional as they depend on interrupts. </descrip> <sect1>DIO Although <htmlurl url="dio.html" name="DIO"> generally works with all ProDOS 8 devices, the function <htmlurl url="dio-3.html" name="dio_query_sectcount()"> simply always return 280 (which is only correct for a 140 KB disk). <sect1>Direct console I/O <descrip> <tag/Color/ The Apple ][ has no color text mode. Therefore the functions <htmlurl url="funcref-205.html" name="textcolor()">, <htmlurl url="funcref-68.html" name="bgcolor()"> and <htmlurl url="funcref-69.html" name="bordercolor()"> have no effect. <tag/Cursor/ The Apple ][ has no hardware cursor. Therefore the function <htmlurl url="funcref-88.html" name="cursor()"> has no effect. </descrip> <sect>Other hints <sect1>Passing arguments to the program Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not supported by BASIC, the following syntax was chosen: <tscreen><verb> ]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5 </verb></tscreen> <enum> <item>Arguments are separated by spaces. <item>Arguments may be quoted. <item>Leading and trailing spaces around an argument are ignored. Spaces within a quoted argument are allowed. <item>The first argument passed to <tt/main/ is the program name. <item>A maximum number of 10 arguments (including the program name) are supported. </enum> <sect1>Interrupts The runtime for the Apple ][ uses routines marked as <tt/.CONDES/ type <tt/interruptor/ for ProDOS 8 interrupt handlers. Such routines must be written as simple machine language subroutines and will be called automatically by the interrupt handler code when they are linked into a program. See the discussion of the <tt/.CONDES/ feature in the <htmlurl url="ca65.html" name="assembler manual">. <sect1>DIO The function <htmlurl url="dio-1.html" name="dio_open()"> has the single parameter <tt/drive_id/ to identify the drive to be opened. Therefore an Apple II slot and drive pair is mapped to that <tt/drive_id/ according to the formula <verb> drive_id = (slot * 2) + (drive - 1) </verb> so that for example slot 6 drive 1 is mapped to <tt/drive_id/ 12. The function <htmlurl url="dio-1.html" name="dio_open()"> succeeds only if a formatted disk is present in the drive. However intentionally no check is performed on the presence of a ProDOS 8 disk. Therefore access to all standard 16-sector disks (as for instance DOS 3.3) is possible. <sect>Bugs/Feedback If you have problems using the library, if you find any bugs, or if you're doing something interesting with it, I would be glad to hear from you. Feel free to contact me by email (<htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">). <sect>License This software is provided 'as-is', without any expressed or implied warranty. In no event will the authors be held liable for any damages arising from the use of this software. Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter it and redistribute it freely, subject to the following restrictions: <enum> <item> The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required. <item> Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. <item> This notice may not be removed or altered from any source distribution. </enum> </article>