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79 lines
2.0 KiB
ArmAsm
79 lines
2.0 KiB
ArmAsm
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; Oliver Schmidt, 2012-09-04
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; Christian Groessler, 2017-12-28
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;
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; unsigned char getfirstdevice (void);
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; unsigned char __fastcall__ getnextdevice (unsigned char device);
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;
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.include "atari.inc"
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.export _getfirstdevice
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.export _getnextdevice
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MAX_DIO_DEVICES = 8
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;------------------------------------------------------------------------------
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; _getfirstdevice
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_getfirstdevice:
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lda #$FF
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; Fall through
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;------------------------------------------------------------------------------
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; _getnextdevice
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_getnextdevice:
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tax
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next: inx
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cpx #MAX_DIO_DEVICES
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beq none
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jsr check_device
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bmi next
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done: txa
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ldx #$00
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rts
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none: ldx #255 ; INVALID_DEVICE (see include/device.h)
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bne done ; jump always
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;------------------------------------------------------------------------------
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; check_device - checks if a disk device is present
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; input: X - device id (0 = D1, 1 = D2, ...)
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; output: NF - 0/1 for detected/not detected
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; X register preserved
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check_device:
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txa
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pha
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lda #SIO_STAT
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sta DCOMND ; set command into DCB
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lda #%01000000 ; direction value, "receive data"
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sta DSTATS ; set data flow directon
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lda #15
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sta DTIMLO ; value got from DOS source
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lda #4
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sta DAUX1 ; set sector # (dummy: 4)
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sta DBYTLO ; # of bytes to transfer
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lda #0
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sta DAUX2
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sta DBYTHI
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lda #>DVSTAT
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sta DBUFHI
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lda #<DVSTAT
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sta DBUFLO ; set buffer address into DCB
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lda #DISKID ; SIO bus ID of diskette drive
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sta DDEVIC
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inx
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stx DUNIT ; unit number (1-based)
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jsr SIOV ; execute SIO command
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pla
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tax
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lda DSTATS
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rts
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.end
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