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some documentation for sim65

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bbbradsmith 2019-05-25 02:56:53 -04:00 committed by Oliver Schmidt
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doc/sim65.sgml
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<abstract> <abstract>
sim65 is a simulator for 6502 and 65C02 CPUs. It allows to test target sim65 is a simulator for 6502 and 65C02 CPUs. It allows to test target
independed code. independent code.
</abstract> </abstract>
<!-- Table of contents --> <!-- Table of contents -->
@ -18,8 +18,8 @@ independed code.
<sect>Overview<p> <sect>Overview<p>
sim65 is the only solution as part of the toolchain to execute code. The sim65 is used as part of the toolchain to test 6502 or 65C02 code.
binary needs to be compiled with <tt/--target sim6502/ or <tt/--target sim65c02/. The binary to test needs to be compiled with <tt/--target sim6502/ or <tt/--target sim65c02/.
<sect>Usage<p> <sect>Usage<p>
@ -104,6 +104,59 @@ PVExit ($01)
</verb></tscreen> </verb></tscreen>
<sect>Creating a Test in C<p>
For a C test compiled and linked with <tt/--target sim65/ the
command line arguments to <tt/sim65/ will be passed to <tt/main/,
and the return value from <tt/main/ will become sim65's exit code.
The <tt/exit/ function may also be used to terminate with an exit code.
Exit codes are limited to 8 bits.
In addition to this, the simulator provides a set of built-in functions
for simple file input and output:
<tscreen><verb>
int open (const char* name, int flags, ...);
int __fastcall__ close (int fd);
int __fastcall__ read (int fd, void* buf, unsigned count);
int __fastcall__ write (int fd, const void* buf, unsigned count);
</verb></tscreen>
<sect>Creating a Test in Assembly<p>
Assembly tests may similarly be assembled ant linked with <tt/--target sim65/,
and the sim65 library provides an <tt/exit/ symbol that the program may <tt/JMP/
to terminate with the current A register value as an exit code.
Without using the provided target library, there are some relevant internal details:
<itemize>
<item>The binary input file has a 1 byte header. A value of 0 indicates 6502 simulation,
and 1 indicates 65C02.
<item>The rest of the input file, after the header, will be loaded at <tt/$0200/,
and execution will begin at <tt/$0200/.
<item>The entire 64 kilobyte address space is writeable RAM.
Aside from the loaded binary, the reset vector at <tt/$FFFC/ will be
pre-loaded with <tt/$0200/ as the start address.
<item>The <tt/exit/ address is <tt/$FFF1/.
Jumping to this address will terminate execution with the A register value as an exit code.
<item>The built-in functions are provided by 6 "paravirtualization" hooks present at
<tt/$FFF0-$FFF5/. Except for <tt/exit/, a <tt/JSR/ to one of these
addresses will return immediately after performing a special function,
intended only for use with the sim65 target C library.
<item><tt/IRQ/ and <tt/NMI/ events will not be generated, though <tt/BRK/
can be used if the IRQ vector at <tt/$FFFE/ is manually prepared by the test code.
</itemize>
<sect>Copyright<p> <sect>Copyright<p>