Fujitsu MAN3735MC Manual/User Guide - Page 126
Servo format, SPM/VCM driver
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Data Head Head IC Read Channel bus8 Processor Servo bus16 DSP bus16 Drive Demodulator I/F LSI Control Signal (PWM) SPM/VCM Combo HDC bus16 MCU ARM7 VCM SPM Notes: DSP controls actuator servo system MCU controls spindle servo system Figure 8.4 Block diagram of servo control circuit (1) Processor-ASIC (Processor-application specific IC) A DSP controls the spindle motor and the voice coil motor. The SCSI sends an instruction to the DSP through the SCSI control MCU via drive interface. The Processor is a 1-chip ASIC, and also contains an analog-to-digital converter, a digital-to-analog converter, RAM, and other logic circuits. (2) Servo demodulator As explained in 8.7.2, servo signals consist of a training segment, a Servo Mark segment, a Position segment and a Gray Code segment, and 120 frames for MAN series are arranged around the circumference. In the servo demodulator, the Gray Code and Position signals from the servo signal are demodulated and used to control head positioning. (3) SPM/VCM driver The SPM driver consists of a controller and a power MOSFET driver. The controller controls the sensor-less spindle motor by checking counter electro-motive voltage, and the driver drives the spindle motor. The VCM driver also consists of a controller and a power MOSFET driver. The controller converts the power amp driver signal output by the digital signal processor (DSP) into a current for driving the VCM, and the driver drives the VCM. The 1-chip SPM/VCM Combo driver contains both power MOSFET drivers. 8.7.2 Servo format (1) Zone format The voice coil motor is controlled to position a data head over a target cylinder, using the servo data that has already been recorded on the data surface. Figure 8.5 shows zone format. 8 - 10 C141-E128-01EN
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