more work on RAM disk support, added ATTIC/CELLAR RAM test

src/dos_m65/unit_ramdisk/unit_rd_preload.s

@@ -0,0 +1,47 @@
+
+;
+; Preload RAM disk image from SD card
+;
+
+
+unit_rd_preload:
+
+	; XXX make sure attic RAM is present
+
+	rts ; XXX remove when code is fully implemented
+
+	; Set file name
+
+	ldy #>ramdisk_filename
+	ldx #<ramdisk_filename
+	lda #$2E                           ; dos_setname
+	sta HTRAP00
+	+nop
+	bcc @error_not_found
+
+	; Try to find the file
+
+	lda #$34                           ; dos_findfile
+	sta HTRAP00
+	+nop
+	bcc @error_not_found               ; branch if file not found
+
+	; XXX load the file
+
+
+
+
+	; lda #$20                           ; dos_closefile
+	; sta HTRAP00
+	; +nop
+
+	; End of initialization
+
+	rts
+
+
+@error_not_found:
+
+	; XXX set information about file not found
+
+	rts