dio implementation by Oliver Schmidt

git-svn-id: svn://svn.cc65.org/cc65/trunk@3432 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/apple2/dioopen.s

@@ -0,0 +1,53 @@
+;
+; Oliver Schmidt, 24.03.2005
+;
+; dhandle_t __fastcall__ dio_open (driveid_t drive_id);
+;
+; drive_id = (slot * 2) + (drive - 1)
+
+        .export 	_dio_open
+        .import		decaxy, return0
+
+        .include	"zeropage.inc"
+        .include	"errno.inc"
+        .include	"mli.inc"
+
+_dio_open:
+        ; Convert drive id into unit number
+        lsr
+        bcc	:+
+        ora	#%00001000
+:       asl
+        asl
+        asl
+        asl
+        sta	mliparam + MLI::ON_LINE::UNIT_NUM
+
+        ; Alloc 16-byte buffer just below stack
+        ldy	#16
+        lda	sp
+        ldx	sp+1
+        jsr	decaxy
+        sta	mliparam + MLI::ON_LINE::DATA_BUFFER
+        stx	mliparam + MLI::ON_LINE::DATA_BUFFER+1
+
+        ; Get device state
+        lda	#ON_LINE_CALL
+        ldx	#ON_LINE_COUNT
+        jsr	callmli
+        bcc	:+
+
+        ; DIO level access doesn't necessarily need a
+        ; ProDOS 8 disk so ignore "high level" errors
+        cmp	#$40
+        bcc	oserr
+
+        ; Return success
+:       lda	mliparam + MLI::ON_LINE::UNIT_NUM
+        ldx	#$00
+        stx	__oserror
+        rts
+
+        ; Return oserror
+oserr:  sta     __oserror
+        jmp	return0