Today’s peripheral storage devices, hard disk drives or solid-state drives, are self-contained sub-systems capable of storing data bits on a magnetic or solid-state medium.  These devices comprise three major components: the storage medium, the read/write sensor, and the system-on-chip (SoC).  These components together determine the achievable storage capacity, reliability, speed, and power consumption of the drive. 

The storage medium in HDDs is a rigid disk, consisting of magnetic materials coated onto a rigid substrate.  Data bits are stored by suitably creating magnetic patterns on the medium.  In SSDs, the medium is a monolithic memory chip, comprising a vast array of pre-fabricated NAND cells whose internal state can be altered to represent data bits. 

The read/write sensor is a transducer which suitably records and retrieves the signals to and from the medium.  The read/write transducer in HDDs converts electrical signals to magnetic fields, and vice versa.  In SSDs, the write transducer alters the charge state of the NAND cell based on the data pattern to be stored; the read transducer senses the charge state of the cell to create a readback electrical signal.

The SoC is the “brains” of the device, residing on the printed circuit board (PCB) with buffer memory and motor control chips.  It embeds the all-important functions of data recovery and data transport, as well as other blocks required to manage the data flow and the functionality of the device. 

The data recovery function performs data encoding to enable reliable retrieval of the stored data in the presence of sensor/medium impairments that include inter-symbol interference, electronics noise, medium and sensor noise, nonlinear distortion, signal drop outs, and stray interferences. It also critically determines how efficiently the media and the read/write sensor are utilized.  If the data recovery method is sub-par, the achievable areal density and reliability are significantly reduced.  On the other hand, powerful data recovery techniques can enable higher areal density, improved product reliability, and higher manufacturing yields.

The data transport function handles the delivery of the recovered data using a prescribed interface protocol. Common interface protocols used in storage devices include Serial Advanced Technology Attachment (SATA), Serial Attached SCSI (SAS), Consumer Electronics ATA (CE-ATA), etc.  Interoperability and compliance with standards specifications of the data transport function are key requirements.  Link_A_Media Devices offers industry-compliant building blocks for standard data transport protocols.