diff --git a/mdttool b/mdttool
index 934185d..e2c0bf1 100755
--- a/mdttool
+++ b/mdttool
@@ -29,6 +29,43 @@ parttab['len2']      = list()
 
 blocksz = 512
 
+# This is 6502 code that must be present in the disk image from offset 0x0200 to 0x03ff
+code_200 = [
+  0x8e, 0x00, 0x82, 0x86, 0x43, 0x8a, 0x4a, 0x4a, 0x4a, 0x4a, 0x09, 0xc0, 0x85, 0x01, 0x8d, 0x81,
+  0x80, 0xa0, 0x00, 0x84, 0x00, 0x84, 0x02, 0xa0, 0xff, 0xb1, 0x00, 0x8d, 0x80, 0x80, 0xa0, 0xf2,
+  0xb1, 0x00, 0xc9, 0xc9, 0xd0, 0x38, 0xc8, 0xb1, 0x00, 0xc9, 0xc4, 0xd0, 0x31, 0xc8, 0xb1, 0x00,
+  0xc9, 0xc5, 0xf0, 0x16, 0xc9, 0xc4, 0xf0, 0x0e, 0x85, 0x02, 0xc9, 0xd2, 0xf0, 0x0c, 0xc9, 0xd5,
+  0xf0, 0x04, 0xc9, 0xd4, 0xd0, 0x18, 0xa9, 0x02, 0xd0, 0x02, 0xa9, 0x00, 0x8d, 0x02, 0x82, 0xa0,
+  0xf9, 0xb1, 0x00, 0xc9, 0xca, 0xd0, 0x07, 0xc8, 0xb1, 0x00, 0xc9, 0xcc, 0xf0, 0x0a, 0x20, 0x58,
+  0xfc, 0x20, 0x39, 0xfb, 0xa0, 0x08, 0xd0, 0x2e, 0x20, 0x5c, 0x81, 0xa0, 0x00, 0x84, 0x46, 0x84,
+  0x47, 0x84, 0x44, 0xc8, 0x84, 0x42, 0xa9, 0x08, 0x85, 0x45, 0xad, 0x00, 0x82, 0x85, 0x43, 0x20,
+  0xff, 0xff, 0xb0, 0x0d, 0xad, 0x00, 0x08, 0xc9, 0x01, 0xd0, 0x06, 0xae, 0x00, 0x82, 0x4c, 0x01,
+  0x08, 0x20, 0x58, 0xfc, 0xa0, 0x06, 0x20, 0x36, 0x81, 0x4c, 0x00, 0xe0, 0xa8, 0x80, 0xc1, 0x80,
+  0xd8, 0x80, 0xf1, 0x80, 0x08, 0x81, 0x1d, 0x81, 0xb0, 0x04, 0xad, 0xad, 0xa0, 0xd2, 0xc1, 0xcd,
+  0xc6, 0xe1, 0xf3, 0xf4, 0xa0, 0xc9, 0xc4, 0xc5, 0xa0, 0xc3, 0xe1, 0xf2, 0xe4, 0xa0, 0xad, 0xad,
+  0x00, 0xb1, 0x04, 0xad, 0xad, 0xa0, 0xd4, 0xf5, 0xf2, 0xe2, 0xef, 0xa0, 0xc9, 0xc4, 0xc5, 0xa0,
+  0xc3, 0xe1, 0xf2, 0xe4, 0xa0, 0xad, 0xad, 0x00, 0xb0, 0x05, 0xa8, 0xe3, 0xa9, 0xa0, 0xb1, 0xb9,
+  0xb9, 0xb6, 0xa0, 0xca, 0xef, 0xe1, 0xe3, 0xe8, 0xe9, 0xed, 0xa0, 0xcc, 0xe1, 0xee, 0xe7, 0xe5,
+  0x00, 0xb1, 0x05, 0xd6, 0xef, 0xec, 0xf5, 0xed, 0xe5, 0xa0, 0xee, 0xef, 0xf4, 0xa0, 0xe6, 0xef,
+  0xf2, 0xed, 0xe1, 0xf4, 0xf4, 0xe5, 0xe4, 0x00, 0xd0, 0x06, 0xc9, 0xc4, 0xc5, 0xa0, 0xc3, 0xe1,
+  0xf2, 0xe4, 0xa0, 0xee, 0xef, 0xf4, 0xa0, 0xe6, 0xef, 0xf5, 0xee, 0xe4, 0x00, 0xd8, 0x07, 0xd6,
+  0xef, 0xec, 0xf5, 0xed, 0xe5, 0xf3, 0xa0, 0xb1, 0xae, 0xae, 0xa0, 0xa0, 0xe1, 0xf6, 0xe1, 0xe9,
+  0xec, 0xe1, 0xe2, 0xec, 0xe5, 0x00, 0xb9, 0x9c, 0x80, 0x85, 0x00, 0xb9, 0x9d, 0x80, 0x85, 0x01,
+  0xa0, 0x00, 0xb1, 0x00, 0x8d, 0x55, 0x81, 0xc8, 0xb1, 0x00, 0x8d, 0x56, 0x81, 0xc8, 0xa2, 0x00,
+  0xb1, 0x00, 0xf0, 0x07, 0x9d, 0xff, 0xff, 0xc8, 0xe8, 0xd0, 0xf5, 0x60, 0xac, 0x02, 0x82, 0x20,
+  0x36, 0x81, 0xa0, 0x04, 0x20, 0x36, 0x81, 0xa5, 0x02, 0xf0, 0xf0, 0xac, 0x1a, 0xc8, 0xc0, 0x02,
+  0x90, 0x11, 0xa5, 0x02, 0xf0, 0x0d, 0xb9, 0xec, 0x81, 0x48, 0xa0, 0x0a, 0x20, 0x36, 0x81, 0x68,
+  0x8d, 0xe3, 0x07, 0xad, 0x61, 0xc0, 0x0d, 0x62, 0xc0, 0x10, 0xd0, 0xa5, 0x02, 0xf0, 0xf4, 0xad,
+  0x00, 0xc0, 0x10, 0xef, 0xc9, 0xba, 0x90, 0x02, 0x29, 0xdf, 0xac, 0x10, 0xc0, 0xac, 0x1a, 0xc8,
+  0xd9, 0xec, 0x81, 0xf0, 0x05, 0x88, 0xd0, 0xf8, 0xf0, 0xd9, 0x88, 0xf0, 0xae, 0x98, 0x0a, 0x0a,
+  0xa8, 0x8c, 0x01, 0x82, 0xa2, 0x00, 0xb9, 0x80, 0xc8, 0x48, 0xbd, 0x80, 0xc8, 0x85, 0x1e, 0x68,
+  0x9d, 0x80, 0xc8, 0xa5, 0x1e, 0x99, 0x80, 0xc8, 0xc8, 0xe8, 0xe0, 0x04, 0x90, 0xe8, 0xac, 0x01,
+  0x82, 0xa2, 0x00, 0xb9, 0x40, 0xc8, 0x48, 0xbd, 0x40, 0xc8, 0x85, 0x1e, 0x68, 0x9d, 0x40, 0xc8,
+  0xa5, 0x1e, 0x99, 0x40, 0xc8, 0xc8, 0xe8, 0xe0, 0x04, 0x90, 0xe8, 0x60, 0xb0, 0xb1, 0xb2, 0xb3,
+  0xb4, 0xb5, 0xb6, 0xb7, 0xb8, 0xb9, 0xc1, 0xc2, 0xc3, 0xc4, 0xc5, 0xc6, 0xc7, 0x00, 0x00, 0x00
+]
+
+
 # Write val as a 16 bit integer into array data[], starting at index start
 def write16(data, start, val):
 	data[start] = val & 0x00ff
@@ -95,7 +132,7 @@ def print_part_tbl():
 # Write partition table in parttab to file f
 # Writes 256 blocks (ie 128K)
 def write_part_tbl(f):
-	magic = 0xcacc
+	magic = 0xccac
 	if ((parttab['cyls'] == -1)
 	    or (parttab['heads'] == -1)
 	    or (parttab['sectors'] == -1)
@@ -119,12 +156,14 @@ def write_part_tbl(f):
 	for i in range(parttab['numparts2']):
 		write32(b, 0x80 + i * 4, parttab['start2'][i])
 		write32(b, 0xa0 + i * 4, parttab['len2'][i])
-	block = bytes(b)
 	with open(f, 'wb') as outfile:
+		block = bytes(b)
 		outfile.write(block)
-		blanks = bytes([0] * blocksz)
-		for i in range(255):
-			outfile.write(blanks)
+		block = bytes(code_200)
+		outfile.write(block)
+		block = bytes([0] * blocksz)
+		for i in range(254):
+			outfile.write(block)
 
 # Extract partition n from file f and write it to outputfile
 def extract_partition(f, n, outputfile):