Abstract: A disk drive circuit that includes a configuration resistor, a reference resistor, a capacitor and a processor. The processor is mounted on a first circuit assembly in the disk drive, such as the controller circuit board, and the configuration resistor is mounted on a second circuit assembly, such as the head-disk assembly (I-IDA). The resistance of the configuration resistor corresponds to the configuration of the second circuit assembly. The configuration may represent the number of heads or the type of preamplifier in the IDA. The processor calculates the resistance of the configuration resistor to determine the configuration of the second circuit assembly in the following manner. The processor charges the capacitor. The processor then allows the capacitor to discharge through a first circuit that includes both the configuration resistor and the reference resistor and measures the discharge time or time constant. The processor again charges the capacitor.

Abstract: A method for controlling a rotating disk magnetic data storage device employing several reduced power modes which are automatically entered and exited under the control of the rotating disk device microcontroller. Two modes are provided which are fully responsive to host computer commands, and are thereby transparent to the host computer user, all providing significant power savings. An additional full power down mode is provided which can be initiated by a command from the host computer user, wherein the operational state parameters of the rotating disk device are stored in the host computer until the host computer powers on the device. At this time the stored state parameter are restored into the rotating disk device allowing it to resume its operational state immediately prior to the power suspension.