Patent ID: 7656607

Claim:
A disk drive comprising: a disk; a head; an actuator for actuating the head over the disk; and control circuitry operable to generate an actuator control signal by: assigning a memory address to a first state variable memory (SVM 1 ); using the memory address to read a first state k variable from the SVM 1 ; storing the first state k variable in a second state variable memory (SVM 2 ) while processing the first state k variable to generate a first state k+1 variable; storing the first state k+1 variable in the SVM 2 ; assigning the memory address to the SVM 2 so that the first state k+1 variable becomes a second state k variable and the first state k variable becomes a first state k−1 variable; using the memory address to read the second state k variable and the first state k−1 variable from the SVM 2 ; storing the second state k variable in the SVM 1 while processing the second state k variable and the first state k−1 variable to generate a second state k+1 variable; storing the second state k+1 variable in the SVM 1 ; and assigning the memory address to the SVM 1 so that the second state k+1 variable becomes a third state k variable.