HOST SOFTWARE INTERFACE
6 – 6
Reset and Interrupt Handling
Reset Handling
One of three different conditions may cause a reset: power on, hardware reset or software reset. All three
cause the interface processor to initialize itself and the Task File registers of the interface. A reset also causes a
set of the Busy bit in the Status register. The Busy bit does not clear until the reset clears and the drive
completes initialization. Completion of a reset operation does not generate a host interrupt.
Task File registers are initialized as follows:
Error
1
Sector Count
1
Sector Number
1
Cylinder Low
0
Cylinder High
0
Drive/Head
0
Interrupt Handling
The drive requests data transfers to and from the host by asserting its IRQ 14 signal. This signal interrupts the
host if enabled by bit 1 (IRQ enable) of the Fixed Disk Control register.
Clear this interrupt by reading the Status register, writing the Command register, or by executing a host
hardware or software reset.
