rework for the initial CBDOS

src/dos_m65/dos_unitchk.s

@@ -0,0 +1,56 @@
+
+;
+; Unit number handling. For detailed description see 'm65dos_bridge.s' file
+;
+
+
+dos_UNITCHK:
+
+	; Check if memory content is not damaged
+
+	jsr dos_MEMCHK
+	bcs dos_UNITCHK_none
+
+	; Check for unit
+
+	cmp UNIT_SDCARD
+	beq dos_UNITCHK_sdcard
+	cmp UNIT_FLOPPY
+	beq dos_UNITCHK_floppy
+	cmp UNIT_RAMDISK
+	beq dos_UNITCHK_ramdisk
+
+	; FALLTROUGH
+
+dos_UNITCHK_none:
+
+	sec
+	rts
+
+dos_UNITCHK_sdcard:
+
+	lda #$00
+	+skip_2_bytes_trash_nvz
+
+	; FALLTROUGH
+
+dos_UNITCHK_floppy:
+
+	lda #$01
+	+skip_2_bytes_trash_nvz
+
+	; FALLTROUGH
+
+dos_UNITCHK_ramdisk:
+
+	lda #$02
+	
+	clc
+	rts
+
+dos_UNITCHK_mem_fail:
+
+	plx
+	pla
+	sec
+	rts