mirror of
https://github.com/elliotnunn/NetBoot.git
synced 2024-09-06 17:54:25 +00:00
132 lines
4.1 KiB
Plaintext
132 lines
4.1 KiB
Plaintext
This chapter documents the backend for the MOS/Rockwell 6502
|
|
microprocessor family. It also supports the Rockwell/WDC 65C02 and the
|
|
Hudson Soft HuC6280 instruction sets.
|
|
|
|
@section Legal
|
|
|
|
This module is written in 2002,2006,2008-2012,2014-2020 by Frank Wille
|
|
and is covered by the vasm copyright without modifications.
|
|
|
|
|
|
@section Additional options for this module
|
|
|
|
This module provides the following additional options:
|
|
|
|
@table @option
|
|
@item -6280
|
|
Recognize all HuC6280 instructions.
|
|
@item -bbcade
|
|
Swap meaning of @code{<} and @code{>} unary operators for compatibility
|
|
with the BBC ADE assembler.
|
|
@item -c02
|
|
Recognize all 65C02 instructions. This excludes DTV (@option{-dtv})
|
|
and illegal (@option{-illegal}) instructions.
|
|
@item -dtv
|
|
Recognize the three additional C64-DTV instructions.
|
|
@item -illegal
|
|
Allow 'illegal' 6502 instructions to be recognized.
|
|
@item -opt-branch
|
|
Enables 'optimization' of B<cc> branches into
|
|
"B<!cc> *+3 ; JMP label" sequences when necessary.
|
|
@item -wdc02
|
|
Recognize all 65C02 instructions and the WDC65C02 extensions
|
|
(RMB,SMB,BBR,BBS,STP,WAI).
|
|
@end table
|
|
|
|
@section General
|
|
|
|
This backend accepts 6502 family instructions as described in
|
|
the instruction set reference manuals from MOS and Rockwell, which are valid
|
|
for the following CPUs: 6502 - 6518, 6570, 6571, 6702, 7501, 8500, 8502.
|
|
|
|
Optionally accepts 65C02 family instructions as decribed in the
|
|
instruction set reference manuals from Rockwell and WDC. Also supports
|
|
the WDC extensions in the W65C02 and W65C134.
|
|
|
|
Optionally accepts 65CE02 family instructions as decribed in the
|
|
instruction set reference manuals from Commodore Semiconductor Group.
|
|
|
|
Optionally accepts HuC6280 instructions as described in the instruction
|
|
set reference manuals from Hudson Soft.
|
|
|
|
The target address type is 16 bit.
|
|
|
|
Instructions consist of one up to three bytes for the standard 6502 family
|
|
(up to 7 bytes for the 6280) and require no alignment.
|
|
There is also no alignment requirement for sections and data.
|
|
|
|
All known mnemonics for illegal instructions are optionally recognized (e.g.
|
|
@code{dcm} and @code{dcp} refer to the same instruction). Some illegal
|
|
insructions (e.g. @code{$ab}) are known to show unpredictable behaviour,
|
|
or do not always work the same on different CPUs.
|
|
|
|
@section Extensions
|
|
|
|
This backend provides the following specific extensions:
|
|
|
|
@itemize @minus
|
|
|
|
@item The parser understands a lo/hi-modifier to select low- or high-byte
|
|
of a 16-bit word. The character @code{<} is used to select the low-byte
|
|
and @code{>} for the high-byte. It has to be the first character before
|
|
an expression.
|
|
|
|
@item When applying the operation @code{/256}, @code{%256} or @code{&256}
|
|
on a label, an appropriate lo/hi-byte relocation will automatically be
|
|
generated.
|
|
|
|
@end itemize
|
|
|
|
This backend extends the selected syntax module by the following
|
|
directives:
|
|
|
|
@table @code
|
|
@item setdp <expr>
|
|
Set the current base address of the zero/direct page for
|
|
optimizations from absolute to zero-page addressing modes.
|
|
Example: set it to @code{$2000} for the HuC6280/PC-Engine.
|
|
|
|
@item zpage <symbol>
|
|
Mark <symbol> as zero page and use zero page addressing for
|
|
expressions based on this symbol.
|
|
@end table
|
|
|
|
@section Optimizations
|
|
|
|
This backend performs the following operand optimizations:
|
|
|
|
@itemize @minus
|
|
|
|
@item Branches, where the destination is out of range, are translated
|
|
into @code{B<!cc> *+3} and an absolute @code{JMP} instruction.
|
|
|
|
@end itemize
|
|
|
|
@section Known Problems
|
|
|
|
Some known problems of this module at the moment:
|
|
|
|
@itemize @minus
|
|
|
|
@item None.
|
|
|
|
@end itemize
|
|
|
|
@section Error Messages
|
|
|
|
This module has the following error messages:
|
|
|
|
@itemize @minus
|
|
|
|
@item 2001: instruction not supported on selected architecture
|
|
@item 2002: trailing garbage in operand
|
|
@item 2003: missing closing parenthesis in addressing mode
|
|
@item 2004: data size %d not supported
|
|
@item 2005: relocation does not allow hi/lo modifier
|
|
@item 2006: operand doesn't fit into %d bits
|
|
@item 2007: branch destination out of range
|
|
@item 2008: illegal bit number
|
|
@item 2009: identifier expected
|
|
|
|
@end itemize
|