mirror of https://github.com/cc65/cc65.git
45 lines
926 B
ArmAsm
45 lines
926 B
ArmAsm
;
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; Marco van den Heuvel, 2018-04-14
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;
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; unsigned char detect_c64dtv (void);
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;
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;/* Check for the presence of the C64DTV.
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; *
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; * Possible return values:
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; * 0x00 : C64DTV not present
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; * 0x01 : C64DTV present
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; */
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.export _detect_c64dtv
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.include "accelerator.inc"
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_detect_c64dtv:
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ldy C64DTV_Extended_Regs
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lda #$00
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ldx $D000
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; Make sure the CPU is a 6510
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.byte $1A ; NOP on 8502, INA on 65(S)C(E)02, 4510 and 65816
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bne not_found
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lda #$01
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sta C64DTV_Extended_Regs
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; Check if $D000 is mirrored at $D040
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cpx $D040
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bne found
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inc $D000
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cpx $D040
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bne not_found
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found:
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lda #$01
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.byte $2C
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not_found:
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lda #$00
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stx $D000
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ldx #$00
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sty C64DTV_Extended_Regs
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rts
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