1a UA (all)
-Mprog doesn's seem to write this:
-After last string
-0x02 0x03 0x01 with PnP == 0
+
+Additional fields after the serial string:
+One byte: 0 - reserved for "legacy port name prefix"
+One byte: 0 - reserved for "legacy port name prefix"
+One byte: 0 - reserved for plug and play options
+(Observed values with PnP == 0:
+0x02 0x03 0x01)
+
+Note: The additional fields after the serial number string
+collide with the official FTDI formula from AN_121 regarding
+the start of the user area:
+"Start Address = the address following the last byte of SerialNumber string."