Fujitsu MHN2150AT Manual/User Guide - Page 60

Theory of Device Operation Power-on Start a) Self-diagnosis 1 - MPU bus test - Internal register write/read test - Work RAM write/read test The spindle motor starts. b) Self-diagnosis 2 - Data buffer write/read test c) Confirming spindle motor speed Load the head assembly d) Initial on-track and read out of system information e) Execute self-calibration f) Drive ready state (command waiting state) End Figure 4.4 Power-on operation sequence 4.5 Self-calibration The disk drive occasionally performs self-calibration in order to sense and calibrate mechanical external forces on the actuator, and VCM torque. This enables precise seek and read/write operations. 4.5.1 Self-calibration contents (1) Sensing and compensating for external forces The actuator suffers from torque due to the FPC forces and winds accompanying disk revolution. The torque vary with the disk drive and the cylinder where the head is positioned. To execute stable fast seek operations, external forces are occasionally sensed. The firmware of the drive measures and stores the force (value of the actuator motor drive current) that balances the torque for stopping head stably. This includes the current offset in the power amplifier circuit and DAC system. 4-8 C141-E120-02EN