MEGA65 glue code for DOS finished

src/kernal/iec_fast/m65dos_bridge.s

@@ -8,44 +8,58 @@
 
 .label VDOS_INIT    = $4000 +  0 * 2
 .label VDOS_CHKUNIT = $4000 +  1 * 2
-.label VDOS_ACPTR   = $4000 +  2 * 2
-.label VDOS_CIOUT   = $4000 +  3 * 2
-.label VDOS_LISTEN  = $4000 +  4 * 2
-.label VDOS_SECOND  = $4000 +  5 * 2
-.label VDOS_TALK    = $4000 +  6 * 2
-.label VDOS_TKSA    = $4000 +  7 * 2
-.label VDOS_UNTLK   = $4000 +  8 * 2
-.label VDOS_UNLSN   = $4000 +  9 * 2
-
-
-// XXX connect this to core IEC implementation
+.label VDOS_SETUNIT = $4000 +  2 * 2
+.label VDOS_ACPTR   = $4000 +  3 * 2
+.label VDOS_CIOUT   = $4000 +  4 * 2
+.label VDOS_LISTEN  = $4000 +  5 * 2
+.label VDOS_SECOND  = $4000 +  6 * 2
+.label VDOS_TALK    = $4000 +  7 * 2
+.label VDOS_TKSA    = $4000 +  8 * 2
+.label VDOS_UNTLK   = $4000 +  9 * 2
+.label VDOS_UNLSN   = $4000 + 10 * 2
 
 
 m65dos_init:
 
+	// Initializes the DOS internal variables
+
 	jsr map_DOS_1
 	jsr_ind VDOS_INIT
 	jmp_8 !+
 
-m65dos_chkunit:
+m65dos_chkunit:                        // XXX expose to BASIC
+
+	// Checks is the unit number is supported by the internal DOS
+	// Input:  .A - unit number to check
+	// Output: Carry set if not supported, otherwise .A contains unit type (0 = SD card, 1 = internal floppy, 2 = RAM disk)
 
 	jsr map_DOS_1
 	jsr_ind VDOS_CHKUNIT
 	jmp_8 !+
 
+m65dos_setunit:                        // XXX expose to BASIC
+
+	// Set the unit number
+	// Input:  .A - unit number, .X - unit type (as in m65dos_chkunit)
+	// Output: Carry set means error
+
+	jsr map_DOS_1
+	jsr_ind VDOS_SETUNIT
+	jmp_8 !+
+
 m65dos_acptr:
 
 	jsr map_DOS_1
 	jsr_ind VDOS_ACPTR
 !:
-	jmp map_NORMAL_from_DOS_1          // try to make ACPTR slightly faster
+	jmp map_NORMAL_from_DOS_1          // ACPTR is slightly faster
 
 m65dos_ciout:
 
 	jsr map_DOS_1
 	jsr_ind VDOS_CIOUT
 !:
-	jmp map_NORMAL_from_DOS_1          // try to make CIOUT slightly faster
+	jmp map_NORMAL_from_DOS_1          // CIOUT is slightly faster
 
 m65dos_listen: