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164 lines
4.3 KiB
ArmAsm
164 lines
4.3 KiB
ArmAsm
;
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; Christian Groessler, February 2005
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;
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; This file provides the _dio_open and _dio_close functions
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; Since on the Atari no real open and close is necessary, they
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; do not open or close something. The _dio_open sets the sector
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; size of the drive which is later used by the _dio_read and
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; _dio_write functions. To query the sector size, the _dio_open
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; accesses the disk drive.
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;
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; dhandle_t __fastcall__ dio_open (unsigned char device);
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; unsigned char __fastcall__ dio_close (dhandle_t handle);
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;
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.export _dio_open, _dio_close
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.export sectsizetab
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.import ___oserror, __sio_call, _dio_read
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.import pushax, addysp, subysp
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.importzp ptr2, sp
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.include "atari.inc"
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.bss
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sectsizetab:
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.res NUMDRVS * sst_size
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.code
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; code for _dio_open
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_inv_drive:
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lda #NONDEV ; non-existent device
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sta ___oserror
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lda #0
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tax
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rts ; return NULL
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_dio_open:
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cmp #NUMDRVS ; valid drive id?
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bcs _inv_drive
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tay ; drive #
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asl a ; make index from drive id
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asl a
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tax
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lda #128 ; preset sectsize
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sta sectsizetab+sst_sectsize,x
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sta sectsizetab+sst_flag,x ; set flag that drive is "open"
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lda #0
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sta sectsizetab+sst_sectsize+1,x
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sta ___oserror ; success
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tya
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sta sectsizetab+sst_driveno,x
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stx ptr2
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lda #<sectsizetab
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clc
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adc ptr2
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sta ptr2
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lda #>sectsizetab
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adc #0
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tax
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stx ptr2+1 ; ptr2: pointer to sectsizetab entry
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; query drive for current sector size
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; procedure:
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; - read sector #4 (SIO command $54) to update drive status;
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; read length is 128 bytes, buffer is allocated on the stack,
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; sector data is ignored;
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; returned command status is ignored, we will get an error with
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; a DD disk anyway (read size 128 vs. sector size 256);
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; - issue SIO command $53 (get status) to retrieve the sector size;
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; use the DVSTAT system area as return buffer;
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; if the command returns with an error, set sector size to 128
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; bytes;
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;
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ldy #128
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jsr subysp ; allocate buffer on the stack
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lda sp
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pha
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lda sp+1
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pha ; save sp (buffer address) on processor stack
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lda ptr2
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ldx ptr2+1
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jsr pushax ; handle
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ldx #0
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lda #4
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jsr pushax ; sect_num
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pla
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tax
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pla ; AX - buffer address
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; sst_sectsize currently 128
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jsr _dio_read ; read sector to update status
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ldy #128
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jsr addysp ; discard stack buffer
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lda ptr2
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ldx ptr2+1
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jsr pushax ; handle
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ldx #0
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lda #4
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jsr pushax ; dummy sector #, ignored by this SIO command,
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; but set to circumvent the special 1-3 sector
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; handling in __sio_call
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ldx #>DVSTAT
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lda #<DVSTAT
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jsr pushax ; buffer address
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ldy #sst_sectsize
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lda #4
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sta (ptr2),y ; 4 bytes transfer
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ldx #%01000000 ; direction value
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lda #SIO_STAT ; get status
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jsr __sio_call
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bmi error
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ldy #sst_sectsize
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lda DVSTAT
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and #%100000
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beq s128
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;s256
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lda #0
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sta (ptr2),y
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iny
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lda #1
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finish: sta (ptr2),y ; set default sector size
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fini2: lda ptr2
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ldx ptr2+1
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rts
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error: ldy #sst_sectsize
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s128: lda #128
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bne finish
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; end of _dio_open
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.proc _dio_close
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sta ptr2
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stx ptr2+1
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lda #0
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ldy #sst_flag
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sta (ptr2),y
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sta ___oserror ; success
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tax
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rts ; return no error
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.endproc
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