Patent ID: 6883122

Claim:
A data reader arranged to read user data and non-user data written across at least two channels of a data-holding medium, said data being arranged into a plurality of data items each including user data and non-user data, said non-user data holding information relating to said user data, the information including write pass number information, and data items written across the said channels at the same time being identified as a set of data items, said write pass number information being included in a header for each said data item, said header including header error detection information, said data reader comprising an arrangement for holding a current write pass number, a read head for reading a respective said channel of said data-holding medium and for thereby deriving a data signal having said data items, and processing circuitry arranged to (a) receive and process said data signals of a set of data items, including processing said write pass number information of each of said data items in said set, (b) receive updating of said current write pass number held by said data reader on the basis of the write pass number information of said data items in said set, and (c) process (i) said header error detection information and (ii) said write pass number information for each said data item in said set before updating said current write pass number.