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174 lines
7.1 KiB
Plaintext
174 lines
7.1 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Synertek Systems Sym-1 specific information for cc65
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<author><url url="mailto:wayne@parhamdata.com" name="Wayne Parham">
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<abstract>
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An overview over the Sym-1 runtime system as it is 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 Sym-1 runtime system as it comes with the cc65 C compiler.
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It describes the memory layout, Sym-1 specific header files, available drivers, and any pitfalls
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specific to the platform.
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Please note that Sym-1 specific functions are just mentioned here, they are described in detail
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in the separate <url url="funcref.html" name="function reference">. Even functions marked as
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"platform dependent" may be available on more than one platform. Please see the
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function reference for more information.
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<sect>Binary format<p>
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The output format generated by the linker for the Sym-1 target is a raw binary BIN file, which
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is essentially a memory image. You can convert this to a HEX file using BIN2HEX, which is a
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popular open-source conversion utility program. A HEX file has ASCII representations of the
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hexadecimal byte values of the machine-language program. So the HEX file can be transferred
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to the Sym-1 using the RS-232 terminal port, just as if the machine-code was entered by hand.
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Enter 'm 200' in the monitor and start the HEX file transfer.
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<p>
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Included with this distribution is a 4k configuration file and a 32k config file. The Sym-1
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on-board memory is limited to 4 kbytes but system memory can be increased to 32 kbytes of
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contiguous RAM with aftermarket add-on boards. So choose the config file that matches your
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system configuration before compiling and linking user programs.
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<sect>Memory layout<p>
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The ROMs and I/O areas are defined in the configuration files, as are most of the entry points
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for useful subroutines in the Sym-1 monitor ROM. cc65 generated programs compiled and linked
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using 4k config run in the memory range of $200 - $0FFF. The 32k config expands
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this range to $7FFF. Memory above 32k can be used to extend the heap, as described below.
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The starting memory location and entry point for running the program is $200, so when the
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program is transferred to the Sym-1, it is executed by typing 'g 200'. The system returns control
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back to the monitor ROM when the program terminates, providing the '.' prompt.
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Special locations:
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<descrip>
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<tag/Text screen/
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Conio support is not currently available for the Sym-1. But stdio console functions are available.
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<tag/Stack/
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The C runtime stack is located at $0FFF on 4kb Syms, or at $7FFF for 32kb systems.
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The stack always grows 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 runtime stack. Extended
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memory can be added to the heap, as described below.
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</descrip><p>
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<sect>Platform specific header files<p>
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Programs containing Sym-1 code may use the <tt/sym1.h/ header file. See the header file for more information.
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<sect1>Hardware access<p>
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The pseudo variables declared in the <tt/sym1.inc/ include file allow access to hardware located in the
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address space. See the include file for more information.
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<sect>Loadable drivers<p>
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<sect1>Graphics drivers<p>
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No graphics drivers are currently available for the Sym-1.
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<sect1>Extended memory drivers<p>
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There are no extended memory drivers for the Sym-1. However, there is a way to access memory beyond the
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32kb boundary, if extended memory is physically present in the system. See the example program,
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symExtendedMemory, in the samples directory.
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<sect1>Joystick drivers<p>
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No joystick driver is currently available for the Sym-1.
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<sect1>Mouse drivers<p>
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No mouse drivers are currently available for the Sym-1.
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<sect1>RS232 device drivers<p>
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No communication port drivers are currently available for the Sym-1. It has only the "master console"
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e.g. stdin and stdout.
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<sect>Limitations<p>
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<sect1>Disk I/O<p>
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The existing library for the Sym-1 doesn't implement C file I/O.
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To be more specific, this limitation means that you cannot use any of the following functions (and a few others):
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<itemize>
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<item>fopen
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<item>fclose
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<item>fread
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<item>fwrite
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<item>...
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</itemize>
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<sect>Other hints<p>
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<sect1>sym1.h<p>
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This header exposes Sym-specific I/O functions that are useful for reading and writing its ports and front panel.
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See the <tt/sym1.h/ include file for a list of the functions available.
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<sect2>Limited memory applications<p>
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As stated earlier, there are config files for 4kb and 32kb systems. If you have 32kb RAM, then you will probably
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want to use the sym1-32k configuration, but if not - if you are using the sym1-4k configuration - then you may
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want to use functions like getchar, putchar, gets and puts rather than functions like scanf and printf.
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Printf, for example, requires about 1KB because it needs to know how to process all the format specifiers.
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<sect3>Using extended memory<p>
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Memory may be physically present that is addressed at locations above the monitor ROM at $8000. This extended
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memory is accessible by adding to the heap, as described in the symExtendedMemory sample program.
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<sect4>Sample programs<p>
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All the samples will run on the "stock" 4kb Sym-1, except for symIO and symNotepad, which require 32kb.
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Additionally, symExtendedMemory shows how to access memory above 32kb, so it expects more than 32kb.
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These sample programs can be found in the samples/sym1 directory:
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<itemize>
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<item>symHello prints "Hello World!" and then inputs characters, which are echoed on the screen.
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It also makes a "beep" sound.</item>
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<item>symTiny does the same as symHello, but does it with puts() rather than printf() to show the difference
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in compiled binary size.</item>
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<item>symDisplay allows entry of a message, which is then displayed by scrolling it across the front panel display.</item>
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<item>symIO allows access to the Sym-1 digital I/O ports.</item>
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<item>symNotepad is a simple text entry/retrieval program that uses tape storage.</item>
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<item>symExtendedMemory demonstrates how to access upper-memory and add it to the heap.</item>
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</itemize>
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<sect>License<p>
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This software is provided 'as-is', without any expressed or implied warranty. In no event will the authors be held
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liable for any damages arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose, including commercial applications, and to alter
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it and redistribute it 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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