DP8473

DP8473 Floppy Disk Controller PLUS-2 July 1990 DP8473 Floppy Disk Controller PLUS-2 TM General Description This controller is a full featured floppy disk controller that is software compatible with the mPD765A but also includes many additional hardware and software enhancements These enhancements include additional logic specifically required for an IBM PC PC-XT PC-AT or PS 2 design This controller incorporates a precision analog data separator that includes a self trimming delay line and VCO Up to three external filters are switched automatically depending on the data rate selected This provides optimal performance at the standard PC data rates of 250 300 kb s and 500 kb s It also enables optimum performance at 1 Mb s (MFM) These features combine to provide the lowest possible PLL bandwidth with the greatest lock range and hence the widest window margin This controller includes write precompensation circuitry A shift register is used to provide a fixed 125 ns early-late precompensation for all tracks at 500k 300k 250 kb s (83 ns for 1 MB s) or a precompensation value that scales with (Continued) Features Y Y Y Y Y Y Fully mPD765A and IBM-BIOS compatible Integrates all PCXT PCAT and most PS 2 Logic On chip 24 MHz Crystal Oscillator DMA enable logic IBM compatible address decode of A0 – A2 12 mA mP bus interface buffers 48 mA floppy drive interface buffers Data rate and drive control registers Precision analog data separator Self-calibrating PLL and delay line Automatic...