2013-09-19 21:21:09 +00:00
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;
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; Macros to disable and enable the ROM on Atari XL systems.
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;
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; Christian Groessler, chris@groessler.org, 19-Sep-2013
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;
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2013-09-19 22:10:34 +00:00
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;
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; Defines which modify the operation of the macros:
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;
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; CHARGEN_RELOC: If defined, CHBAS and CHBASE are updated when
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; enabling or disabling the ROM.
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; If the ROM is enabled, $E0 is written to CHBAS
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; and CHBASE.
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; If the ROM is disabled, the upper byte of
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; __CHARGEN_START__ is written to CHBAS and CHBASE.
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; USEWSYNC: If defined, the code waits for horizontal retrace
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; before switching the ROM and updating CHBAS and
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2013-09-19 22:26:49 +00:00
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; CHBASE. This define only has effect if CHARGEN_RELOC
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2013-09-19 22:10:34 +00:00
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; is also defined.
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2013-09-19 21:21:09 +00:00
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.ifdef __ATARIXL__
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2013-09-19 22:10:34 +00:00
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.ifdef CHARGEN_RELOC
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.macro set_chbase val
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lda #val
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sta CHBAS
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sta CHBASE
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.endmacro
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2013-10-16 15:55:45 +00:00
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.else ; above CHARGEN_RELOC, below not
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2013-09-19 22:10:34 +00:00
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.macro set_chbase val
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.endmacro
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.endif ; .ifdef CHARGEN_RELOC
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2013-09-19 21:34:45 +00:00
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.if .defined(USEWSYNC) .and .defined(CHARGEN_RELOC)
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2013-09-19 22:10:34 +00:00
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2013-09-19 21:21:09 +00:00
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.macro wsync
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sta WSYNC
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.endmacro
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2013-09-19 22:10:34 +00:00
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2013-10-16 15:55:45 +00:00
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.else ; above USEWSYNC, below not
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2013-09-19 22:10:34 +00:00
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2013-09-19 21:21:09 +00:00
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.macro wsync
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.endmacro
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2013-09-19 22:10:34 +00:00
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2013-09-19 21:21:09 +00:00
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.endif
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2013-09-19 22:10:34 +00:00
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; "disable ROM" macros
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2013-09-19 21:21:09 +00:00
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.macro disable_rom
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lda PORTB
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and #$fe
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wsync
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sta PORTB
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2013-09-19 22:10:34 +00:00
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set_chbase >__CHARGEN_START__
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2013-09-19 21:21:09 +00:00
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.endmacro
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2013-09-19 22:10:34 +00:00
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2013-09-19 21:21:09 +00:00
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.macro disable_rom_quick
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lda PORTB
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and #$fe
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sta PORTB
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2013-09-19 22:10:34 +00:00
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set_chbase >__CHARGEN_START__
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2013-09-19 21:21:09 +00:00
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.endmacro
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2013-09-19 22:10:34 +00:00
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2013-09-19 21:21:09 +00:00
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.macro disable_rom_val val
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lda val
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wsync
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sta PORTB
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2013-09-19 22:10:34 +00:00
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set_chbase >__CHARGEN_START__
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2013-09-19 21:21:09 +00:00
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.endmacro
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2013-09-19 22:10:34 +00:00
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; "enable ROM" macros
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2013-09-19 21:21:09 +00:00
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.macro enable_rom
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lda PORTB
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ora #1
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wsync
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sta PORTB
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2013-09-19 22:10:34 +00:00
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set_chbase $E0
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2013-09-19 21:21:09 +00:00
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.endmacro
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2013-09-19 22:10:34 +00:00
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2013-09-19 21:21:09 +00:00
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.macro enable_rom_quick
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lda PORTB
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ora #1
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sta PORTB
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2013-09-19 22:10:34 +00:00
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set_chbase $E0
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2013-09-19 21:21:09 +00:00
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.endmacro
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.else ; above __ATARIXL__, below not
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.macro disable_rom
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.endmacro
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.macro enable_rom
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.endmacro
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.endif
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