updates to floppy code

src/dos_m65/lowlevel/lowlevel_fd_helpers.s

@@ -1,84 +0,0 @@
-
-; Helper routines for low-level disk operations
-
-
-lowlevel_fd_ensure_presence_refresh:
-
-	jsr lowlevel_fd_wait_clr_BUSY     ; to be extra sure
-
-	; XXX stepping head is definitely needed, but probably still not enough
-
-	; lda #%00011000                     ; step head 1 track in (XXX: check if it is really in)
-	; sta FDC_COMMAND  ; $D081
-	; jsr lowlevel_fd_wait_clr_BUSY
-
-	; lda #%00010000                     ; step head 1 track out (XXX: check if it is really out)
-	; sta FDC_COMMAND  ; $D081
-	; jsr lowlevel_fd_wait_clr_BUSY
-
-	; FALLTROUGH
-
-lowlevel_fd_ensure_presence:
-
-	lda FDC_STATUS_B ; $D083           ; check if disk is inserted
-	and #$08
-	beq @not_present
-	rts
-
-@not_present:
-
-	pla
-	pla
-
-	jsr lowlevel_fd_motor_off          ; if disk not present, disable drive motor
-
-	; XXX set error code, invalidate buffers, etc.
-
-	sec
-	rts
-
-lowlevel_fd_motor_on:
-
-	lda FDC_CONTROL
-	and #%00100000
-	bne lowlevel_fd_rts               ; if motor already enabled, do nothing
-
-	; XXX find out why it is not disabled at all 
-	; lda #%00100000                     ; enable drive motor and LED
-	; tsb FDC_CONTROL  ; $D080
-
-	; Allow some time for spin-up; according to https://wiki.osdev.org/Floppy_Disk_Controller
-	; 300 ms should be more than enough
-	
-	; XXX reenable this
-	; phx
-	; ldx #$0F
-	; jsr wait_x_bars
-	; plx
-
-	bra lowlevel_fd_wait_clr_BUSY
-
-lowlevel_fd_motor_off:
-
-	lda #%00100000                     ; disable drive motor and LED
-	trb FDC_CONTROL  ; $D080
-
-	; FALLTROUGH
-
-lowlevel_fd_wait_clr_BUSY:
-
-	bit FDC_STATUS_A ; $D082
-	bmi lowlevel_fd_wait_clr_BUSY
-
-	rts
-
-lowlevel_fd_wait_set_RDREQ:
-
-	bit FDC_STATUS_B ; $D083
-	bpl lowlevel_fd_wait_set_RDREQ
-
-	; FALLTROUGH
-
-lowlevel_fd_rts:
-
-	rts

src/dos_m65/lowlevel/lowlevel_fd_readsector.s

@@ -1,5 +1,6 @@
 
-; Read a sector pair from a block device
+; Read a sector pair from a block device, flow partially based on:
+; - https://github.com/MEGA65/mega65-tools/blob/master/src/tests/floppytest.c
 
 
 lowlevel_xx_readsector:
@@ -11,48 +12,46 @@ lowlevel_xx_readsector:
 
 lowlevel_fd_readsector:
 
-	; Set drive
+	; Check if buffer contains data from given track, sector, drive
-
-	lda #%00001111                     ; set drive 0 (internal) and side 0
-	trb FDC_CONTROL  ; $D080
-
-	cpx #$01
-	beq @1
-
-	lda #%00000001                     ; if needed, switch to drive 1 (external)
-	tsb FDC_CONTROL
-@1:
-	; Ensure disk is present
-
-	jsr lowlevel_fd_ensure_presence_refresh
-
-	; Check if buffer contains data from given track
-	; XXX compare device and unit too
 
 	lda PAR_TRACK
 	cmp BUFTAB_TRACK+1
-	bne lowlevel_readsector_force
+	bne lowlevel_fd_readsector_force
- 
-	; Check if sectors match
 
 	lda PAR_SECTOR
 	and #%11111110
 	cmp BUFTAB_SECTOR+1
-	bne lowlevel_readsector_force
+	bne lowlevel_fd_readsector_force
+
+	; XXX compare drive
 
 	; Data already loaded into buffer - do nothing
 
 	clc
 	rts
 
-lowlevel_readsector_force:
+lowlevel_fd_readsector_force:
 
-	jsr lowlevel_fd_motor_on           ; enable drive motor and LED
+	; Set drive, motor ON
-	jsr lowlevel_fd_ensure_presence
 
-	lda #%10000000                     ; select floppy buffer
+	lda #$68
+	cpx #$01
+	beq @1
+	inc
+@1:
+	sta FDC_CONTROL  ; $D080
+
+	; Select floppy buffer
+
+	lda #%10000000
 	trb SD_BUFCTL    ; $D689
 
+	; Wait until BUSY flag clears
+
+@2:
+	lda FDC_STATUS_A ; $D082
+	bmi @2
+
 	; Select physical track and sector based on logical ones from PAR_TRACK and PAR_SECTOR
 
 	lda PAR_TRACK
@@ -84,21 +83,30 @@ lowlevel_readsector_force:
 	inc
 	sta FDC_SECTOR   ; $D085
 
+	; Reset buffers
+
+	lda #$00
+	sta FDC_COMMAND  ; $D081
+
 	; Ask the controller to read the sector    XXX how to detect errors, missing disk, etc.?
 
 	lda #$40
 	sta FDC_COMMAND  ; $D081
 
-	jsr lowlevel_fd_wait_set_RDREQ     ; wait till sector is found
+	; Wait for busy flag to assert   XXX how much? 1 second? most likelly too much...
-	jsr lowlevel_fd_wait_clr_BUSY      ; wait for BUSY flag to clear
 
-	; Wait for DRQ and EQ flags to go high
+	ldy #71
+@3:
+	ldx #$00
+	jsr wait_x_bars
+	dey
+	bne @3
 
-@lp1:
+	; Wait until BUSY flag clears
+
+@4:
 	lda FDC_STATUS_A ; $D082
-	and #%01100000
+	bmi @4
-	cmp #%01000000   ; XXX is this correct? .A seems to stay at $40 at this point
-	bne @lp1
 
 	; Copy sector to buffer in RAM
 
@@ -125,3 +133,13 @@ lowlevel_readsector_force:
 
 	clc
 	rts
+
+
+
+lowlevel_fd_motor_off:
+
+	; XXX set correct drive
+
+	lda #$00
+	sta FDC_CONTROL  ; $D080
+	rts