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e47485f925
For quite some time I deliberately didn't add cursor support to the Apple II CONIO imöplementation. I consider it inappropriate to increase the size of cgetc() unduly for a rather seldom used feature. There's no hardware cursor on the Apple II so displaying a cursor during keyboard input means reading the character stored at the cursor location, writing the cursor character, reading the keyboard and finally writing back the character read initially. The naive approach is to reuse the part of cputc() that determines the memory location of the character at the cursor position in order to read the character stored there. However that means to add at least one additional JSR / RTS pair to cputc() adding 4 bytes and 12 cycles :-( Apart from that this approach means still a "too" large cgetc(). The approach implemented instead is to include all functionality required by cgetc() into cputc() - which is to read the current character before writing a new one. This may seem surprising at first glance but an LDA(),Y / TAX sequence adds only 3 bytes and 7 cycles so it cheaper than the JSR / RTS pair and allows to brings down the code increase in cgetc() down to a reasonable value. However so far the internal cputc() code in question saved the X register. Now it uses the X register to return the old character present before writing the new character for cgetc(). This requires some rather small adjustments in other functions using that internal cputc() code.
543 lines
18 KiB
Plaintext
543 lines
18 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Enhanced Apple //e specific information for cc65
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<author><url url="mailto:ol.sc@web.de" name="Oliver Schmidt">
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<date>2014-04-10
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<abstract>
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An overview over the enhanced Apple //e runtime system as it is
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implemented for the cc65 C compiler.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<sect>Overview<p>
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This file contains an overview of the enhanced Apple //e runtime system
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as it comes with the cc65 C compiler. It describes the memory layout,
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enhanced Apple //e specific header files, available drivers, and any
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pitfalls specific to that platform.
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Please note that enhanced Apple //e specific functions are just mentioned
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here, they are described in detail in the separate <url url="funcref.html"
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name="function reference">. Even functions marked as "platform dependent" may
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be available on more than one platform. Please see the function reference for
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more information.
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<sect>Binary format<p>
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The standard binary file format generated by the linker for the
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enhanced Apple //e target is a binary program with a 4 byte DOS 3.3 header
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containing the load address and load length. The default load address is
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$803.
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<bf/AppleCommander 1.3.5/ or later (available at <url
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url="http://applecommander.sourceforge.net/">) includes the option <tt/-cc65/
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that allows to put binary files with a DOS 3.3 header onto disk images
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containing DOS 3.3 as well as ProDOS 8.
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For ProDOS 8 system programs the load address is fixed to $2000 so there
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is no need for a header. Thus the linker configuration
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<ref id="apple-sys-cfg" name="apple2enh-system.cfg"> for those programs
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omits the DOS 3.3 header. The right AppleCommander option to put system files
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without a header on a ProDOS 8 disk image is <tt/-p/.
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<sect>Memory layout<p>
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In the standard setup, cc65 generated programs use the memory from
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$803 to $95FF, so 35.5 KB of RAM are available.
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Special locations:
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<descrip>
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<tag/Stack/
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The C runtime stack is located at HIMEM and grows downwards, regardless of
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how your linker config file is setup.
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<tag/Heap/
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The C heap is located at the end of the program and grows towards the C
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runtime stack.
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</descrip><p>
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While running <tt/main()/ the Language Card bank 2 is enabled for read access.
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However while running module constructors/destructors the Language Card is disabled.
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Enabling the Language Card allows to use it as additional memory for cc65
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generated code. However code is never automatically placed there. Rather code
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needs to be explicitly placed in the Language Card either per file by compiling
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with <tt/--code-name LC/ or per function by enclosing in <tt/#pragma code-name
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(push, "LC")/ and <tt/#pragma code-name (pop)/. In either case the cc65 runtime
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system takes care of actually moving the code into the Language Card.
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The amount of memory available in the Language Card for generated code depends
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on the <ref id="link-configs" name="linker configuration"> parameters. There are
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several usefull settings:
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<descrip>
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<tag>LC address: $D400, LC size: $C00</tag>
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For plain vanilla ProDOS 8 which doesn't actually use the Language Card bank 2
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memory from $D400 to $DFFF. This is the default setting.
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<tag>LC address: $D000, LC size: $1000</tag>
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For ProDOS 8 together with the function <tt/rebootafterexit()/. If a program
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doesn't quit to the ProDOS 8 dispatcher but rather reboots the machine after
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exit then a plain vanilla ProDOS 8 doesn't make use of the Language Card bank
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2 at all.
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<tag>LC address: $D000, LC size: $3000</tag>
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For plain vanilla DOS 3.3 which doesn't make use of the Language Card at all.
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</descrip><p>
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<sect>Linker configurations<label id="link-configs"><p>
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The ld65 linker comes with a default config file for the enhanced Apple //e,
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which is used via <tt/-t apple2enh/.
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The apple2enh package comes with additional secondary linker config files, which
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are used via <tt/-t apple2enh -C <configfile>/.
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<sect1>default config file (<tt/apple2enh.cfg/)<label id="apple-def-cfg"><p>
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Default configuration for a binary program.
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Parameters:
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<descrip>
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Default: $803. Use <tt/-S <addr>/ to set a different start address.
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<tag><tt/__EXEHDR__:/ Executable file header</tag>
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Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
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the header.
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<tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
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Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
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stack size.
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<tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
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Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
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highest usable address.
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<tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
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Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
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code address.
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<tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
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Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
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code size.
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</descrip><p>
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<sect1><tt/apple2enh-system.cfg/<label id="apple-sys-cfg"><p>
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Configuration for a system program running on ProDOS 8 and using the memory from
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$2000 to $BEFF.
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Parameters:
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<descrip>
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<tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
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Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
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stack size.
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<tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
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Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
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code address.
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<tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
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Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
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code size.
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</descrip><p>
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<sect1><tt/apple2enh-overlay.cfg/<p>
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Configuration for overlay programs with the up to nine overlays. The overlay files
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don't include the DOS 3.3 header. See <tt>samples/overlaydemo.c</tt> for more
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information on overlays.
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Parameters:
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<descrip>
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Default: $803. Use <tt/-S <addr>/ to set a different start address.
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<tag><tt/__EXEHDR__:/ Executable file header</tag>
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Default: DOS 3.3 header (address and length). Use <tt/-D __EXEHDR__=0/ to omit
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the header.
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<tag><tt/__STACKSIZE__:/ C runtime stack size</tag>
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Default: $800. Use <tt/-D __STACKSIZE__=<size>/ to set a different
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stack size.
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<tag><tt/__HIMEM__:/ Highest usable memory address presumed at link time</tag>
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Default: $9600. Use <tt/-D __HIMEM__=<addr>/ to set a different
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highest usable address.
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<tag><tt/__LCADDR__:/ Address of code in the Language Card</tag>
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Default: $D400. Use <tt/-D __LCADDR__=<addr>/ to set a different
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code address.
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<tag><tt/__LCSIZE__:/ Size of code in the Language Card</tag>
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Default: $C00. Use <tt/-D __LCSIZE__=<size>/ to set a different
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code size.
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<tag><tt/__OVERLAYSIZE__:/ Size of code in the overlays</tag>
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Default: $1000. Use <tt/-D __OVERLAYSIZE__=<size>/ to set a different
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code size.
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</descrip><p>
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<sect1><tt/apple2enh-asm.cfg/<p>
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Configuration for a assembler programs which don't need a special setup.
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Parameters:
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<descrip>
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<tag><tt/STARTADDRESS:/ Program start address</tag>
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Default: $803. Use <tt/-S <addr>/ to set a different start address.
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<tag><tt/__EXEHDR__:/ Executable file header</tag>
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Default: No header. Use <tt/-u __EXEHDR__ apple2enh.lib/ to add a DOS 3.3 header
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(address and length).
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</descrip><p>
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<sect>ProDOS 8 system programs<p>
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ProDOS 8 system programs are always loaded to the start address $2000.
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For cc65 programs this means that the 6 KB from $800 to $2000 are
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by default unused. There are however several options to make use of that memory
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range.
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<sect1>LOADER.SYSTEM<p>
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The easiest (and for really large programs in fact the only) way to have a cc65
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program use the memory from $800 to $2000 is to link it as binary
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(as opposed to system) program using the default linker configuration
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<ref id="apple-def-cfg" name="apple2enh.cfg"> with <tt/__HIMEM__/set to $BF00
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and load it with the LOADER.SYSTEM utility. The program then works like a system
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program (i.e. quits to the ProDOS dispatcher).
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Using LOADER.SYSTEM is as simple as copying it to the ProDOS 8 directory of the
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program to load under name <program>.SYSTEM as a system program. For
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example the program <tt/MYPROG/ is loaded by <tt/MYPROG.SYSTEM/.
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<sect1>Heap<p>
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If the cc65 program can be successfully linked as system program using the linker
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configuration <ref id="apple-sys-cfg" name="apple2enh-system.cfg">, but
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uses the heap either explicitly or implicitly (i.e. by loading a driver) then
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the memory from $800 to $2000 can be added to the heap by calling
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<tt/_heapadd ((void *) 0x0800, 0x1800);/ at the beginning of <tt/main()/.
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<sect1>ProDOS 8 I/O buffers<p>
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ProDOS 8 requires for every open file a page-aligned 1 KB I/O buffer. By default
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these buffers are allocated by the cc65 runtime system on the heap using
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<tt/posix_memalign()/. While this is generally the best solution it means quite
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some overhead for (especially rather small) cc65 programs which do open files
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but don't make use of the heap otherwise.
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The apple2enh package comes with the alternative ProDOS 8 I/O buffer allocation
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module <tt/apple2enh-iobuf-0800.o/ which uses the memory between $800 and
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the program start address for the 1 KB I/O buffers. For system programs (with
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start address $2000) this results in up to 6 I/O buffers and thus up to 6
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concurrently open files.
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While using <tt/_heapadd()/ as described in the section above together with the
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default I/O buffer allocation basically yields the same placement of I/O buffers
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in memory the primary benefit of <tt/apple2enh-iobuf-0800.o/ is a reduction in code
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size - and thus program file size - of more than 1400 bytes.
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Using <tt/apple2enh-iobuf-0800.o/ is as simple as placing it on the linker command
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line like this:
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<tscreen><verb>
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cl65 -t apple2enh -C apple2enh-system.cfg myprog.c apple2enh-iobuf-0800.o
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</verb></tscreen>
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<sect>Platform specific header files<p>
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Programs containing enhanced Apple //e specific code may use the
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<tt/apple2enh.h/ header file.
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<sect1>Enhanced Apple //e specific functions<p>
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The functions listed below are special for the enhanced Apple //e. See
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the <url url="funcref.html" name="function reference"> for declaration and
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usage.
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<itemize>
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<item>_auxtype
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<item>_dos_type
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<item>_filetype
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<item>get_ostype
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<item>rebootafterexit
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<item>ser_apple2_slot
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<item>textframe
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<item>textframexy
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<item>tgi_apple2_mix
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<item>videomode
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</itemize>
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<sect1>Hardware access<p>
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There's currently no support for direct hardware access. This does not mean
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you cannot do it, it just means that there's no help.
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<sect>Loadable drivers<p>
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The names in the parentheses denote the symbols to be used for static linking of the drivers.
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<sect1>Graphics drivers<p>
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<descrip>
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<tag><tt/a2e.lo.tgi (a2e_lo_tgi)/</tag>
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This driver features a resolution of 40×48 with 16 colors.
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The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
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function clears the corresponding area at the bottom of the screen.
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<tag><tt/a2e.hi.tgi (a2e_hi_tgi)/</tag>
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This driver features a resolution of 280×192 with 8 colors and two
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hires pages. Note that programs using this driver will have to be linked
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with <tt/-S $4000/ to reserve the first hires page or with <tt/-S $6000/
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to reserve both hires pages.
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Note that the second hires page is only available if the text display is not in
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80 column mode. This can be asserted by calling <tt/videomode (VIDEOMODE_40COL);/
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before installing the driver.
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The function <tt/tgi_apple2_mix()/ allows to activate 4 lines of text. The
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function doesn't clear the corresponding area at the bottom of the screen.
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In memory constrained situations the memory from $803 to $1FFF
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can be made available to a program by calling <tt/_heapadd ((void *) 0x0803, 0x17FD);/
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at the beginning of <tt/main()/. Doing so is beneficial even if the program
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doesn't use the the heap explicitly because loading the driver (and in fact
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already opening the driver file) uses the heap implicitly.
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</descrip><p>
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<sect1>Extended memory drivers<p>
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<descrip>
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<tag><tt/a2e.auxmem.emd (a2e_auxmem_emd)/</tag>
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Gives access to 47.5 KB RAM (190 pages of 256 bytes each) on an Extended
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80-Column Text Card.
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Note that this driver doesn't check for the actual existence of the memory
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and that it doesn't check for ProDOS 8 RAM disk content!
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</descrip><p>
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<sect1>Joystick drivers<p>
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<descrip>
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<tag><tt/a2e.stdjoy.joy (a2e_stdjoy_joy)/</tag>
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Supports up to two standard analog joysticks connected to the game port of
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the enhanced Apple //e.
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</descrip><p>
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<sect1>Mouse drivers<p>
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<descrip>
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<tag><tt/a2e.stdmou.mou (a2e_stdmou_mou)/</tag>
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Driver for the AppleMouse II Card. Searches all Apple II slots
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for an AppleMouse II Card compatible firmware. The default bounding
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box is [0..279,0..191].
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Note that the enhanced Apple //e default mouse callbacks support
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text mode only.
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</descrip><p>
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<sect1>RS232 device drivers<p>
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<descrip>
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<tag><tt/a2e.ssc.ser (a2e_ssc_ser)/</tag>
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Driver for the Apple II Super Serial Card. Supports up to 19200 baud,
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hardware flow control (RTS/CTS) and interrupt driven receives. Note
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that because of the peculiarities of the 6551 chip transmits are not
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interrupt driven, and the transceiver blocks if the receiver asserts
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flow control because of a full buffer.
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The driver defaults to slot 2. Call <tt/ser_apple2_slot()/ prior to
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<tt/ser_open()/ in order to select a different slot. <tt/ser_apple2_slot()/
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succeeds for all Apple II slots, but <tt/ser_open()/ fails with
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<tt/SER_ERR_NO_DEVICE/ if there's no SSC firmware found in the selected slot.
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</descrip><p>
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<sect>Limitations<p>
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<sect1>DOS 3.3<p>
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Although the standard binaries generated by the linker for the enhanced Apple //e
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generally run both on DOS 3.3 (with Applesoft BASIC) and on ProDOS 8 (with
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BASIC.SYSTEM) there are some limitations for DOS 3.3:
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<descrip>
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<tag>Disk File I/O</tag>
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There's no disk file I/O support. Any attempt to use it yields an error with
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<tt/errno/ set to <tt/ENOSYS/. This implicitly means that loadable drivers
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are in general not functional as they depend on disk file I/O. Therefore the statically
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linked drivers have to be used instead.
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<tag/Interrupts/
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There's no <tt/interruptor/ support. Any attempt to use it yields the message
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'Failed to alloc interrupt' on program startup. This implicitly means that
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<tt/a2e.stdmou.mou/ and <tt/a2e.ssc.ser/ are not functional as they depend on
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interrupts.
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</descrip><p>
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<sect1>Direct console I/O<p>
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<descrip>
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<tag/Color/
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The enhanced Apple //e has no color text mode. Therefore the functions
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textcolor(), bgcolor() and bordercolor() have no effect.
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</descrip><p>
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<sect>Other hints<p>
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<sect1>Passing arguments to the program<p>
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Command line arguments can be passed to <tt/main()/ after BLOAD. Since this is not
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supported by BASIC, the following syntax was chosen:
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<tscreen><verb>
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]CALL2051:REM ARG1 " ARG2 IS QUOTED" ARG3 "" ARG5
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</verb></tscreen>
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<enum>
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<item>Arguments are separated by spaces.
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<item>Arguments may be quoted.
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<item>Leading and trailing spaces around an argument are ignored. Spaces within
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a quoted argument are allowed.
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<item>The first argument passed to <tt/main/ is the program name.
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<item>A maximum number of 10 arguments (including the program name) are
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supported.
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</enum>
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<sect1>Function keys<p>
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These are defined to be OpenApple + number key.
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<sect1>Interrupts<p>
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The runtime for the enhanced Apple //e uses routines marked as
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<tt/.INTERRUPTOR/ for ProDOS 8 interrupt handlers. Such routines must be
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written as simple machine language subroutines and will be called
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automatically by the interrupt handler code when they are linked into a
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program. See the discussion of the <tt/.CONDES/ feature in the <url
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url="ca65.html" name="assembler manual">.
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<sect1>DIO<p>
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<descrip>
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<tag/Drive ID/
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The function <url url="dio.html#s1" name="dio_open()"> has the single
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parameter <tt/device/ to identify the device to be opened. Therefore an
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Apple II slot and drive pair is mapped to that <tt/device/ according
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to the formula
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<tscreen>
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device = slot + (drive - 1) * 8
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</tscreen>
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so that for example slot 6 drive 2 is mapped to <tt/device/ 14.
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<tag/Sector count/
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The function <url url="dio.html#s3" name="dio_query_sectcount()"> returns
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the correct sector count for all ProDOS 8 disks. However for any non-ProDOS 8
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disk it simply always returns 280 (which is only correct for a 140 KB disk).
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This condition is indicated by the <tt/_oserror/ value 82.
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</descrip><p>
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<sect>License<p>
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This software is provided 'as-is', without any expressed or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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<enum>
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<item> The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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<item> Altered source versions must be plainly marked as such, and must not
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be misrepresented as being the original software.
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<item> This notice may not be removed or altered from any source
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distribution.
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</enum>
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</article>
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