Abstract: Error information is passed across a limited interface from a disk drive to its using system by making use of the read data line during a fault mode operation. Fault mode operation is detected by a pulse width detector in an adapter between the using system and the disk drive. The pulse width detector detects the presence of a fault signal on the read data line and inhibits the passage of the spindle motor on (MTR ON) signal from the using system to the disk drive. The step signal normally used to index the recording head is passed to the disk drive during fault mode operation. A microcomputer at the disk drive detects the absence of the MTR ON signal and the presence of the step signal and outputs a fault data bit. Thereafter, the fault data word is gated onto the read data line at the rate of one bit per step of the step signal so long as the MTR ON signal is absent.

Abstract: A braking system for an electrical stepping motor having its rotor mechanically connected to drive a transducer carriage of a magnetic disk drive machine, the braking system including a transistor which is responsive to the voltage across the stator coils of the stepping motor and initiates the controlled discharging of a capacitor. The charge on the capacitor is effective through transistor control circuits so as to short all of the stator coils, with the exception of the one to which an energizing voltage is applied for locating the rotor in its target position, when the capacitor discharges in a predetermined time so as to brake the rotor as the rotor approaches its target position on a return movement after the rotor initially passes across its target position.