dos33fsprogs/games/mist_hgr/lc_detect.s

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2021-07-08 04:57:11 +00:00
; Code from TotalReplay by 4am and qkumba
;------------------------------------------------------------------------------
; Has64K
; Checks whether computer has functioning language card (64K)
;
; in: none
; out: C clear if 64K detected
; C set if 64K not detected
; all other flags and registers clobbered
; ROM in memory (not LC RAM bank)
;------------------------------------------------------------------------------
detect_language_card:
; enable language card
; READ_RAM1_WRITE_RAM1
bit $C08B
bit $C08B
lda #$AA ; test #1 for $D0 page
sta $D000
eor $D000
bne no_lc
lsr $D000 ; test #2 for $D0 page
lda #$55
eor $D000
bne no_lc
clc
bcc done_detect
no_lc:
sec
done_detect:
; READ_ROM_NO_WRITE
bit $C08A
rts