Older models of computers, electronic musical instruments and industrial automation often used floppy disk drives for data transfer.
A typical floppy disk controller sends an MFM / FM / GCR encoded signal to the drive to write data, and expects a similar signal returned when reading the drive.
[6] On a write, a hardware PLL or a software-based filter component undoes the encoding, and stores the sector data as logically written by the host.
Most FDC interfaces do not directly address tracks; instead they provide "step-in" and "step-out" pulses.
This may require the emulator to provide buffering, with some delay in updating the permanent storage.