Development of a programmable computer interface circuit: a four diskette drive adapter

The function of a floppy disk controller (FDC) is to interface the microprocessor of a system to the disk drive. This FDC adapter is designed for double-density, MFM-coded four diskette drives and uses a write precompensation with an analog Phase-locked loop and data recovery. The adapter is a general-purpose device, using the NEC VL6765- 08PC compatible controller chip, which is programmable. The diskette drive write protect feature is also supported. The FDC is buffered on the I/O bus and uses DMA for record data transfers.