HD63265 Floppy Disk Controller Users Manual 2ed Mar89 - Bitsavers

9.5 FDC CONTROL9.5.1 FDC Operating StatesThe FDC has three operating states as follows.1. IDLE state: Usual command wait state2. SLEEP mode: Low power dissipation mode, and also command wait state3. Execution state: State during command execution9.5.2 Interrupt ServicingThe FOC generates the IRQ signal in the following four cases:1. Data read/write request in Non-DMA (PIO) mode2. Result status read request at the termination of READ/WRITE commands3. Starting request of CHECK INTERRUPT STATUS command at the termination of aSEEK or RECALIBRATE operation4. Starting request of CHECK INTERRUPT STATUS command when the READY signalfrom an FDD has changed state since it was polled last time.Thus, a host computer detects IRQ of the FDC, reads the status register,identifies which of the above cases caused the interrupt, and then servicesthe request, accordingly.9.6 HOST INTERFACEThe following examples show how to connect the FDC to the 80-series and68-series 8-bit bus systems.9.6.1 80-Series 8-Bit Bus SystemFigure 9-9 shows a typical FDC interface circuit for a HD64B180-based80-series 8-bit bus system.HITACHI 97