commented out some problematic code

src/dos_m65/lowlevel/lowlevel_helpers_fdc.s

@@ -8,13 +8,13 @@ lowlevel_fdc_ensure_presence_refresh:
 
 	; 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_fdc_wait_clr_BUSY
+	; lda #%00011000                     ; step head 1 track in (XXX: check if it is really in)
+	; sta FDC_COMMAND  ; $D081
+	; jsr lowlevel_fdc_wait_clr_BUSY
 
-	lda #%00010000                     ; step head 1 track out (XXX: check if it is really out)
-	sta FDC_COMMAND  ; $D081
-	jsr lowlevel_fdc_wait_clr_BUSY
+	; lda #%00010000                     ; step head 1 track out (XXX: check if it is really out)
+	; sta FDC_COMMAND  ; $D081
+	; jsr lowlevel_fdc_wait_clr_BUSY
 
 	; FALLTROUGH
 
@@ -39,16 +39,22 @@ lowlevel_fdc_ensure_presence:
 
 lowlevel_fdc_motor_on:
 
-	lda #%00100000                     ; enable drive motor and LED
-	tsb FDC_CONTROL  ; $D080
+	lda FDC_CONTROL
+	and #%00100000
+	bne lowlevel_fdc_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
 	
-	phx
-	ldx #$0F
-	jsr wait_x_bars
-	plx
+	; XXX reenable this
+	; phx
+	; ldx #$0F
+	; jsr wait_x_bars
+	; plx
 
 	bra lowlevel_fdc_wait_clr_BUSY
 
@@ -71,4 +77,8 @@ lowlevel_fdc_wait_set_RDREQ:
 	bit FDC_STATUS_B ; $D083
 	bpl lowlevel_fdc_wait_set_RDREQ
 
+	; FALLTROUGH
+
+lowlevel_fdc_rts:
+
 	rts

src/dos_m65/lowlevel/lowlevel_readsector.s

@@ -85,8 +85,6 @@ lowlevel_readsector_force:
 	cmp #%01000000   ; XXX is this correct? .A seems to stay at $40 at this point
 	bne @lp1
 
-	jsr lowlevel_fdc_motor_off         ; disable drive motor
-
 	; Copy sector to buffer in RAM
 
 	lda #$00

src/dos_m65/unit_floppy/unit_fd_cmd_close.s

@@ -8,4 +8,6 @@ unit_fd_cmd_CLOSE:
 
 	; XXX provide implementation
 
+	jsr lowlevel_fdc_motor_off         ; disable drive motor  XXX only do this if no channel is opened
+
 	jmp dos_EXIT_SEC