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337 lines
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337 lines
10 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Commodore 128 specific information for cc65
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<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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<date>2003-12-14
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<abstract>
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An overview over the C128 runtime system as it is implemented for the cc65 C
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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 C128 runtime system as it comes with the
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cc65 C compiler. It describes the memory layout, C128 specific header files,
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available drivers, and any pitfalls specific to that platform.
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Please note that C128 specific functions are just mentioned here, they are
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described in detail in the separate <htmlurl url="funcref.html" name="function
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reference">. Even functions marked as "platform dependent" may be available on
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more than one platform. Please see the function reference for more
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information.
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<sect>Binary format<p>
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The standard binary output format generated by the linker for the C128 target
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is a machine language program with a one line BASIC stub. This means that a
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program can be loaded as BASIC program and started with RUN. It is of course
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possible to change this behaviour by using a modified startup file and linker
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config.
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<sect>Memory layout<p>
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cc65 generated programs with the default setup run with the I/O area and the
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kernal ROM enabled. Note that this is a non standard memory layout, and that
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there is no "memory configuration index" for this layout. This means that
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special case has to be taken when changing the configuration, or calling any
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code that does this. The memory configuration register at $FF00 should
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be saved and restored instead of relying on the memory configuration index
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stored in the zero page.
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The setup gives a usable memory range of $1C00 - $CFFF. Having
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just the kernal ROM mapped in means, that kernal entry points may be called
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directly, but using the BASIC ROM is not possible without additional code.
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Special locations:
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<descrip>
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<tag/Text screen/
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The text screen is located at $400 (as in the standard setup).
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<tag/Stack/
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The C runtime stack is located at $CFFF and growing downwards.
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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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<sect>Platform specific header files<p>
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Programs containing C128 specific code may use the <tt/c128.h/ or <tt/cbm.h/
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header files. Using the later may be an option when writing code for more than
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one CBM platform, since it includes <tt/c128.h/ and declares several functions
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common to all CBM platforms.
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<sect1>C128 specific functions<p>
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The functions listed below are special for the C128. See the <htmlurl
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url="funcref.html" name="function reference"> for declaration and usage.
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<itemize>
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<item>toggle_videomode
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<item>c64mode
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<item>fast
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<item>slow
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</itemize>
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<sect1>CBM specific functions<p>
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Some functions are available for all (or at least most) of the Commodore
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machines. See the <htmlurl url="funcref.html" name="function reference"> for
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declaration and usage.
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<itemize>
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<item>cbm_close
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<item>cbm_closedir
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<item>cbm_k_setlfs
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<item>cbm_k_setnam
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<item>cbm_k_load
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<item>cbm_k_save
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<item>cbm_k_open
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<item>cbm_k_close
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<item>cbm_k_readst
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<item>cbm_k_chkin
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<item>cbm_k_ckout
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<item>cbm_k_basin
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<item>cbm_k_bsout
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<item>cbm_k_clrch
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<item>cbm_load
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<item>cbm_open
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<item>cbm_opendir
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<item>cbm_read
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<item>cbm_readdir
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<item>cbm_save
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<item>cbm_write
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<item>get_tv
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</itemize>
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<sect1>Hardware access<p>
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The following pseudo variables declared in the <tt/c128.h/ header file do
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allow access to hardware located in the address space. Some variables are
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structures, accessing the struct fields will access the chip registers.
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<descrip>
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<tag><tt/VIC/</tag>
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The <tt/VIC/ structure allows access to the VIC II (the graphics
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controller). See the <tt/_vic2.h/ header file located in the include
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directory for the declaration of the structure.
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<tag><tt/SID/</tag>
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The <tt/SID/ structure allows access to the SID (the sound interface
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device). See the <tt/_sid.h/ header file located in the include directory
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for the declaration of the structure.
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<tag><tt/VDC/</tag>
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The <tt/VDC/ structure allows access to the VDC (the video display
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controller). See the <tt/_vdc.h/ header file located in the include
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directory for the declaration of the structure.
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<tag><tt/CIA1, CIA2/</tag>
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Access to the two CIA (complex interface adapter) chips is available via
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the <tt/CIA1/ and <tt/CIA2/ variables. The structure behind these variables
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is explained in <tt/_6526.h/.
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<tag><tt/COLOR_RAM/</tag>
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A character array that mirrors the color RAM of the C64 at $D800.
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</descrip><p>
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<sect>Loadable drivers<p>
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<sect1>Graphics drivers<p>
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Note: The graphics drivers for the VDC are incompatible with the extended
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memory drivers using the VDC memory!
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<descrip>
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<tag><tt/c128-vdc.tgi/</tag>
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This driver was written by Maciej Witkowiak. It uses the 80 column display
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and features a resolution of 640*200 with two colors and an adjustable
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palette (that means that the two colors can be chosen out of the 16 VDC
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colors).
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<tag><tt/c128-vdc2.tgi/</tag>
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This driver was written by Maciej Witkowiak. This driver uses the 80 column
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display and features a resolution of 640*480 with two colors and an
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adjustable palette (that means that the two colors can be chosen out of the
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16 VDC colors). The driver requires 64KB VDC RAM.
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</descrip><p>
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Note: The colors are translated from definitions in headers to correct VDC values
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so please use definitions or VIC color numbers only. Colors <tt/GRAY3/ and <tt/BROWN/ are
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missing on VDC and are translated to the two colors missing from VIC palette.
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<sect1>Extended memory drivers<p>
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<descrip>
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<tag><tt/c128-georam.emd/</tag>
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A driver for the GeoRam cartridge. The driver will always assume 2048 pages
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of 256 bytes each. There are no checks, so if your program knows better,
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just go ahead.
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<tag><tt/c128-ram.emd/</tag>
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An extended memory driver for the RAM in page 1. The common memory area is
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excluded, so this driver supports 251 pages of 256 bytes each.
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<tag><tt/c128-ramcart.emd/</tag>
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A driver for the RamCart 64/128 written and contributed by Maciej Witkowiak.
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Will test the hardware for the available RAM.
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<tag><tt/c128-reu.emd/</tag>
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A driver for the CBM REUs. The driver will determine from the connected REU
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if it supports 128KB of RAM or more. In the latter case, 256KB are assumed,
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but since there are no range checks, the application can use more memory if
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it has better knowledge about the hardware than the driver.
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<tag><tt/c128-vdc.emd/</tag>
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A driver for the VDC memory of the C128 written and contributed by Maciej
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Witkowiak. Autodetects the amount of memory available (16 or 64K) and offers
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64 or 256 pages of 256 bytes each. Note: This driver is incompatible with
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any of the graphics drivers using the VDC!
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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/c128-ptvjoy.joy/</tag>
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Driver for the Protovision 4-player adapter originally written by Groepaz
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for the C64 and converted for the C128 by me. See <htmlurl
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url="http://www.protovision-online.de/hardw/hardwstart.htm"
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name="http://www.protovision-online.de/hardw/hardwstart.htm"> for prices and
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building instructions. Up to four joysticks are supported.
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<tag><tt/c128-stdjoy.joy/</tag>
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Supports up to two joysticks connected to the standard joysticks port of
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the C128.
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</descrip><p>
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<sect1>Mouse drivers<p>
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Currently no drivers available (in fact, the API for loadable mouse drivers
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does not exist).
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<sect1>RS232 device drivers<p>
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<descrip>
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<tag><tt/c128-swlink.ser/</tag>
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Driver for the SwiftLink cartridge. Supports up to 38400 baud, hardware flow
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control (RTS/CTS) and interrupt driven receives. Note that because of the
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peculiarities of the 6551 chip together with the use of the NMI, transmits
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are not 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 uses the RS232 variables and buffers of the kernal (buffers at
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$C00 and $D00).
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</descrip><p>
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<sect>Limitations<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()/. 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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RUN: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>Program return code<p>
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The program return code (low byte) is passed back to BASIC by use of the
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<tt/ST/ variable.
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<sect1>Interrupts<p>
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The runtime for the C128 uses routines marked as <tt/.CONDES/ type 2 for
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interrupt handlers. Such routines must be written as simple machine language
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subroutines and will be called automatically by the interrupt handler code
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when they are linked into a program. See the discussion of the <tt/.CONDES/
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feature in the <htmlurl url="ca65.html" name="assembler manual">.
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<sect>Bugs/Feedback<p>
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If you have problems using the library, if you find any bugs, or if you're
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doing something interesting with it, I would be glad to hear from you. Feel
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free to contact me by email (<htmlurl url="mailto:uz@cc65.org"
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name="uz@cc65.org">).
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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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