The hard disk control circuit is divided into the following parts: main control chip, data transfer chip, high-speed data cache chip, etc. The main control chip is responsible for hard disk data read/write instructions and other tasks. The data transfer chip reads the data from the head pre-control circuit of the hard disk, corrects and transforms it, and then transmits it to the host system via the data interface. The high-speed data cache chip is designed to coordinate the difference in data processing speed between the hard disk and the host. The effect of the cache on disk performance is undeniable. When reading scattered file data, a large cache can bring significant performance advantages. This is why there have been high-end SCSI hard drives with 8MB data cache products.
In terms of the working principle of the hard drive, it uses the polarity of specific magnetic particles to record data. When the head reads data, it converts the different polarities of magnetic particles into different electrical pulse signals, and then uses a data converter to transform these raw signals into data that the computer can use. Writing operations are just the opposite. In addition, there is also a storage buffer in the hard drive, which is set up to coordinate the difference in data processing speed between the hard disk and the host. Since the structure of the hard disk is much more complex than that of a floppy disk, its formatting work is also heavier, including low-level formatting, hard disk partitioning, hard disk recovery, high-level formatting, and establishing a file system.
After the hard disk drive is powered on and working normally, the initialization module of the microcontroller in the control circuit performs initialization work, at this time the head is located at the center of the disk. After initialization is completed, the spindle motor will start and rotate at high speed. The carriage mechanism that carries the floating head moves to position the floating head on track 00 of the disk surface, waiting for command initiation. When the interface circuit receives instruction signals transferred from the microcomputer system, it drives the voice coil motor to emit magnetic signals through the pre-amplifier control circuit. Based on the change in inductive resistance, the head positions the data information on the disk and decodes the received data information, transmitting it through the amplifier control circuit to the interface circuit, feeding back to the host system to complete the instruction operation. After the hard disk operation ends and power is cut off, the floating head returns to rest at the center of the disk under the action of the counter-torque spring.
Original article by Hefei Data Recovery Center: http://www.cndr.cn/hydt/12917.html