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Merge pull request #2774 from mrdudz/somedocs

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Somedocs
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Bob Andrews
2025-07-07 23:27:14 +02:00
committed by GitHub
parent 7c6efded1c cf89172cf7
commit 593bf159fa
2 changed files with 97 additions and 41 deletions
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@@ -1434,38 +1434,6 @@ constant is defined:
CPU_ISET_M740
</verb></tscreen>
<!-- Sorry but explaining these with the changes from #2751 is too cringy for
me - must be done by someone else. The remainder is from the old
".macpack cpu" section"
The value read from the <tt/<ref id=".CPU" name=".CPU">/ pseudo variable may
be checked with <tt/<ref id="operators" name=".BITAND">/ to determine if the
currently enabled CPU supports a specific instruction set. For example the
65C02 supports all instructions of the 65SC02 CPU, so it has the
<tt/CPU_ISET_65SC02/ bit set in addition to its native <tt/CPU_ISET_65C02/
bit. Using
<tscreen><verb>
.if (.cpu .bitand CPU_ISET_65SC02)
lda (c_sp)
.else
ldy #$00
lda (c_sp),y
.endif
</verb></tscreen>
it is possible to determine if the
<tscreen><verb>
lda (c_sp)
</verb></tscreen>
instruction is supported, which is the case for the 65SC02, 65C02 and 65816
CPUs (the latter two are upwards compatible to the 65SC02).
see section <ref id="6502-mode" name="6502 format"> and following.
-->
<tt/.CPU/ may be used to replace the .IFPxx pseudo instructions or to
construct even more complex expressions.
@@ -1483,8 +1451,43 @@ see section <ref id="6502-mode" name="6502 format"> and following.
.endif
</verb></tscreen>
See also: <tt><ref id=".CAP" name=".CAP"></tt>
<bf>The dilemma:</bf>
The original design of this feature was made under the assumption, that any
"higher" CPU will support the entire instruction set of the "lower" CPU. For
example: the WDC W65C02 supports all instructions of the 65C02, which again
support all instructions of the 65SC02. Unfortunately this is not true for all
CMOS CPUs - when the 65CE02 was made, some instructions were changed, and a new
addressingmode was added. As a result all CPUS after (and including) 65CE02
are no more (source code) compatible with all instructions originally introduced
by the 65SC02.
Because of this, the .CPU function and the ISET* macros were repurposed to
indicate <em>groups of instructions</em> only, ie only the set of instructions
that was added by that particular CPU. In the value returned by .CPU only the
bits will be set, that refer to the groups of instructions that are completely
supported by that CPU.
The advantage of this is, that the mechanism keeps working for all new CPUs
added. The inevitable disadvantage is that you now have to know exactly which
CPU added which instructions (look <htmlurl url="cpus.html" name="here"> for reference).
<tscreen><verb>
.if (.cpu .bitand CPU_ISET_65SC02)
; This will be assembled for the W65C02, 65C02, 65SC02, 65816, HUC6820
lda (c_sp)
.elseif (.cpu .bitand CPU_ISET_65CE02)
; This will be assembled for the 65CE02, 4510, 45GS02
ldz #$00
lda (c_sp),z
.else
ldy #$00
lda (c_sp),y
.endif
</verb></tscreen>
See also: <tt><ref id=".CAP" name=".CAP"></tt>, which is a similar mechanism,
but without the problem outlined above.
<sect1><tt>.ISIZE</tt><label id=".ISIZE"><p>
@@ -3807,7 +3810,6 @@ See: <tt><ref id=".ASCIIZ" name=".ASCIIZ"></tt>,<tt><ref id=".BYTE" name=".BYTE"
<tscreen><verb>
atari Defines the scrcode macro.
cbm Defines the scrcode macro.
cpu Defines constants for the .CPU variable.
generic Defines generic macros like add, sub, and blt.
longbranch Defines conditional long-jump macros.
</verb></tscreen>
@@ -5121,6 +5123,7 @@ For better orthogonality, the assembler defines similar symbols as the
compiler, depending on the target system selected:
<itemize>
<item><tt/__AGAT__/ - Target system is <tt/agat/
<item><tt/__APPLE2__/ - Target system is <tt/apple2/ or <tt/apple2enh/
<item><tt/__APPLE2ENH__/ - Target system is <tt/apple2enh/
<item><tt/__ATARI2600__/ - Target system is <tt/atari2600/
@@ -5133,23 +5136,31 @@ compiler, depending on the target system selected:
<item><tt/__C128__/ - Target system is <tt/c128/
<item><tt/__C16__/ - Target system is <tt/c16/ or <tt/plus4/
<item><tt/__C64__/ - Target system is <tt/c64/
<item><tt/__C65__/ - Target system is <tt/c65/
<item><tt/__CBM__/ - Target is a Commodore or Commodore-alike system
<item><tt/__CBM510__/ - Target system is <tt/cbm510/
<item><tt/__CBM610__/ - Target system is <tt/cbm610/
<item><tt/__CREATIVISION__/ - Target system is <tt/creativision/
<item><tt/__CX16__/ - Target system is <tt/cx16/
<item><tt/__GAMATE__/ - Target system is <tt/gamate/
<item><tt/__GEOS__/ - Target is a GEOS system
<item><tt/__GEOS_APPLE__/ - Target system is <tt/geos-apple/
<item><tt/__GEOS_CBM__/ - Target system is <tt/geos-cbm/
<item><tt/__KIM1__/ - Target system is <tt/kim1/
<item><tt/__LUNIX__/ - Target system is <tt/lunix/
<item><tt/__LYNX__/ - Target system is <tt/lynx/
<item><tt/__MEGA65__/ - Target system is <tt/mega65/
<item><tt/__NES__/ - Target system is <tt/nes/
<item><tt/__OSIC1P__/ - Target system is <tt/osic1p/
<item><tt/__PCE__/ - Target system is <tt/pce/
<item><tt/__PET__/ - Target system is <tt/pet/
<item><tt/__PLUS4__/ - Target system is <tt/plus4/
<item><tt/__RP6502__/ - Target system is <tt/rp6502/
<item><tt/__SIM6502__/ - Target system is <tt/sim6502/
<item><tt/__SIM65C02__/ - Target system is <tt/sim65c02/
<item><tt/__SUPERVISION__/ - Target system is <tt/supervision/
<item><tt/__SYM1__/ - Target system is <tt/sym1/
<item><tt/__TELESTRAT__/ - Target system is <tt/telestrat/
<item><tt/__VIC20__/ - Target system is <tt/vic20/
</itemize>