Patent ID: 7640483

Claim:
An error detecting code calculation circuit that calculates an error detecting code for detecting an error in a user data code string having a first sequence, the circuit processing data in units of data groups including two or more sectors containing the user data code string, each data group including an operation target sector having a structure that the error detecting code is appeared in an end of the user data code string when read in the first sequence and the error detecting code is appeared in a middle of the user data code string when read in a different sequence from the first sequence, the error detecting code calculation circuit comprising: a first operation section for calculating an error detecting code intermediate value from a part of user data in the operation target sector; and a second operation section for calculating an error detecting code from a remaining part of user data in the operation target sector and the error detecting code intermediate value, wherein the second operation section calculates the error detecting code to be added to the user data code string contained in the operation target sector that is read in the different sequence from the first sequence.