<article>
-<title>Commodore 610 specific information for cc65
-<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
-<date>2003-12-16
+<title>Commodore 610-specific information for cc65
+<author>
+<url url="mailto:uz@cc65.org" name="Ullrich von Bassewitz">,<newline>
+<url url="mailto:greg.king5@verizon.net" name="Greg King">
+<date>2014-04-25
<abstract>
An overview over the Commodore 610 runtime system as it is implemented for the
<sect>Overview<p>
This file contains an overview of the CBM 610 runtime system as it comes with
-the cc65 C compiler. It describes the memory layout, CBM 610 specific header
+the cc65 C compiler. It describes the memory layout, CBM 610-specific header
files, available drivers, and any pitfalls specific to that platform.
-Please note that CBM 610 specific functions are just mentioned here, they are
-described in detail in the separate <htmlurl url="funcref.html" name="function
+Please note that CBM 610-specific functions are just mentioned here, they are
+described in detail in the separate <url 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.
In addition to the Commodore 610 (named B40 in the U.S.), several other
machines are supported by this cc65 target, since they have identical
hardware: The Commodore 620 and 630 (more memory, additional coprocessor
-card), and the Commodore 710, 720 and 730 (same hardware in another case with
-a builtin monitor).
+card), and the Commodore 710, 720, and 730 (same hardware in another case with
+a built-in monitor).
<sect>Binary format<p>
-The standard binary output format generated by the linker for the CBM610
-target is a machine language program with a short BASIC stub. This means that
-a program can be loaded as BASIC program and started with RUN. It is of course
-possible to change this behaviour by using a modified startup file and linker
+The standard binary output format generated by the linker for the Commodore
+610 target is a machine language program with a one-line BASIC stub, which
+transfers control to the machine language running in bank 1. That means that a
+program can be loaded as a BASIC program, and started with RUN. It is, of course,
+possible to change that behaviour by using a modified startup file and linker
config.
+
<sect>Memory layout<p>
cc65 generated programs for the Commodore 610 run in bank 1, the memory bank
-reserved for BASIC programs. Since there are no ROMs in this memory bank, the
-program has almost full 64K for its own. A disadvantage is that kernal
-subroutines cannot be called (at least not in a fast and effective manner), so
-the runtime has replace kernal functionality.
+reserved for BASIC programs. Since there are no ROMs in this memory bank,
+kernal subroutines are either emulated or called by bank switching, which has
+the disadvantage of being slow compared to a direct call.
The default memory configuration for the CBM 610 allocates all memory between
$0002 and $FFF0 in bank 1 for the compiled program. Some space
in low memory is lost, because a separate hardware stack is set up in page 1,
and the kernal replacement functions need some more memory locations. A few
-more bytes are lost in high memory, because the runtime sets up a CBM
-compatible jump table at $FF81. The main startup code is located at
+more bytes are lost in high memory, because the runtime sets up a CBM-compatible
+jump table at $FF81. The main startup code is located at
$0400, so about 63K of the complete bank are actually usable for
applications.
-<bf>Note:</bf> The zero page from $02 to $5F is free to use for
-applications!
-
Special locations:
<descrip>
<tag/Stack/
- The C runtime stack is located at $FF81 and growing downwards.
+ The C runtime stack is located at $FF81, and grows downwards.
<tag/Heap/
- The C heap is located at the end of the program and grows towards the C
+ The C heap is located at the end of the program, and grows towards the C
runtime stack.
</descrip><p>
-<sect>Platform
specific header files<p>
+<sect>Platform
-specific header files<p>
-Programs containing CBM 610 specific code may use the <tt/cbm610.h/ or
+Programs containing CBM 610-specific code may use the <tt/cbm610.h/ or
<tt/cbm.h/ header files. Using the later may be an option when writing code
-for more than one CBM platform, since it includes <tt/cbm610.h/ and declares
+for more than one CBM platform, since it includes <tt/cbm610.h/, and declares
several functions common to all CBM platforms.
-Please note that because of <ref id="limitations" name="current limitations">
-of the runtime library for the platform, several standard C and CBM functions
-are not available.
+<sect1>CBM 610-specific functions<p>
-<sect1>CBM 610 specific functions<p>
-
-The functions listed below are special for the CBM 610. See the <htmlurl
+The functions listed below are special for the CBM 610. See the <url
url="funcref.html" name="function reference"> for declaration and usage.
<itemize>
<item>peekbsys
-<item>peewsys
+<item>peekwsys
<item>pokebsys
<item>pokewsys
</itemize>
-<sect1>CBM
specific functions<p>
+<sect1>CBM
-specific functions<p>
Some functions are available for all (or at least most) of the Commodore
-machines. See the <htmlurl url="funcref.html" name="function reference"> for
+machines. See the <url url="funcref.html" name="function reference"> for
declaration and usage.
+<itemize>
+<item>cbm_close
+<item>cbm_closedir
+<item>cbm_k_setlfs
+<item>cbm_k_setnam
+<item>cbm_k_load
+<item>cbm_k_save
+<item>cbm_k_open
+<item>cbm_k_close
+<item>cbm_k_readst
+<item>cbm_k_chkin
+<item>cbm_k_ckout
+<item>cbm_k_basin
+<item>cbm_k_bsout
+<item>cbm_k_clrch
+<item>cbm_k_tksa
+<item>cbm_k_second
+<item>cbm_load
+<item>cbm_open
+<item>cbm_opendir
+<item>cbm_read
+<item>cbm_readdir
+<item>cbm_save
+<item>cbm_write
+<item>get_tv
+</itemize>
+
+
<sect1>Hardware access<p>
The following pseudo variables declared in the <tt/cbm610.h/ header file do
allow access to hardware located in the address space. Some variables are
-structures, accessing the struct fields will access the chip registers.
+structures; accessing the struct fields will access the chip registers.
-<bf>Note:</bf> All I/O chips are located in the system bank (bank 15) and can
+<em/Note:/ All I/O chips are located in the system bank (bank 15); and can
therefore not be accessed like on other platforms. Please use one of the
-<tt/peekbsys/, <tt/peewsys/, <tt/pokebsys/ and <tt/pokewsys/ functions to
+<tt/peekbsys/, <tt/peekwsys/, <tt/pokebsys/, and <tt/pokewsys/ functions to
access the I/O chips. Direct reads and writes to the structures named below
will <em>not</em> work!
declaration of the structure.
<tag><tt/TPI1, TPI2/</tag>
- The two 6525 triport chips may be accessed by using this variable. See the
+ The two 6525 triport chips may be accessed by using these variables. See the
<tt/_6525.h/ header file located in the include directory for the
declaration of the structure.
<sect>Loadable drivers<p>
-<bf>Note:</bf> Since the CBM 610 doesn't have working disk I/O (see <ref
-id="limitations" name="section "Limitations"">), the available
-drivers cannot be loaded at runtime (so the term "loadable drivers" is
-somewhat misleading). Instead, the drivers have to be converted using the
-<htmlurl url="co65.html" name="co65 utility"> and statically linked. While
-this may seem overhead, it has two advantages:
-
-<enum>
-<item>The interface is identical to the one used for other platforms
- and to the one for the CBM 610 once it has disk I/O.
-<item>Once disk I/O is available, existing code can be changed to load drivers
- at runtime with almost no effort.
-</enum>
+The names in the parentheses denote the symbols to be used for static linking of the drivers.
<sect1>Graphics drivers<p>
No graphics drivers are currently available for the Commodore 610 (and since
the machine has no graphics capabilities, chances for a graphics driver aren't
-really good:-).
+really good :-).
<sect1>Extended memory drivers<p>
<descrip>
- <tag><tt/cbm610-ram.emd/</tag>
+ <tag><tt/cbm610-ram.emd (cbm610_ram_emd)/</tag>
A driver for the RAM in bank 2. Supports up to 255 pages with 256 bytes
- each. Untested!
+ each.
</descrip><p>
<sect1>Joystick drivers<p>
-The Commodore 610 is a business machine and doesn't have joystick ports. There
-are no drivers for the non existing ports available.
-
+The Commodore 610 is a business machine, and doesn't have joystick ports. There
+are no drivers for the non-existing ports available.
<sect1>Mouse drivers<p>
-Currently no drivers available (in fact, the API for loadable mouse drivers
-does not exist).
+No mouse drivers are currently available for the Commodore 610.
<sect1>RS232 device drivers<p>
-Currently no RS232 drivers exist for the Commodore 610.
+<descrip>
+
+ <tag><tt/cbm610-std.ser (cbm610_std_ser)/</tag>
+ Driver for the 6551 ACIA chip built into the Commodore 610. Supports up to
+ 19200 BPS, 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.
+
+</descrip><p>
<sect>Limitations<label id="limitations"><p>
-<sect1>Disk I/O<p>
-
-The existing library for the CBM 610 doesn't implement C file I/O. Please note
-that this includes <tt/printf/! You may use the conio functions for screen I/O.
+<sect1>Kernal and hardware access<p>
-To be more concrete, this limitation means that you cannot use any of the
-following functions (and a few others):
+Since the program runs in bank 1, and the kernal and all I/O chips are located
+in bank 15, calling ROM routines or accessing hardware needs special code. The
+cc65 runtime implements wrappers for all functions in the kernal jump table.
+While this simplifies things, it should be noted that the wrappers do have
+quite an impact on performance: A cross-bank call has an extra 300µs
+penalty added by the wrapper.
-<itemize>
-<item>fclose
-<item>fgets
-<item>fopen
-<item>fread
-<item>fprintf
-<item>fputc
-<item>fscanf
-<item>fwrite
-<item>gets
-<item>printf
-<item>...
-</itemize>
+<sect1>Interrupts<p>
-<sect1>Kernal and hardware access<p>
+Compiled programs contain an interrupt handler that runs in the program bank.
+This has several advantages, one of them being performance (see cross-bank
+call overhead mentioned above). However, this introduces one problem:
+Interrupts are lost while the CPU executes code in the kernal bank. As a
+result, the clock may go wrong; and (worse), serial interrupts may get lost.
-Since the program runs in bank 1, and the kernal and all I/O chips are located
-in bank 15, calling ROM routines or accessing hardware needs special code.
+Since the cc65 runtime does only call the kernal for disk I/O, this means that
+a program should not do file I/O while it depends on interrupts.
<sect>Other hints<p>
+
<sect1>Passing arguments to the program<p>
-Command line argument passing is currently not supported for the Commodore
-610.
+Command-line arguments can be passed to <tt/main()/. Since that is not
+supported directly by BASIC, the following syntax was chosen:
+
+<tscreen><verb>
+ RUN: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>Program return code<p>
+The program return code (low byte) is passed back to BASIC by use of the
+<tt/ST/ variable.
-<sect>Bugs/Feedback<p>
-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">).
+<sect1>Interrupt handlers<p>
+
+The runtime for the Commodore 610 uses routines marked as <tt/.INTERRUPTOR/
+for 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 <url url="ca65.html" name="assembler manual">.
</enum>
</article>
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-
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projects / cc65 / blobdiff