Table of Contents
Advertisement
4.1.4
SEEK MODE
The read/write head carriage is mounted on a threaded shaft connected to the stepper motor. As the
stepper motor turns in one direction, the head is stepped outward toward the edge of the diskette.
When the motor turns in the other direction, the head is stepped inward toward the spindle hub.
This allows access to any track on the diskette. Direction Select from the interface or controller
determines the direction of rotation of the stepper motor, while the number of Step pulses deter-
mines the amount of stepper-motor rotation. The control logic translates these input pulses into a
sequential pattern of phase currents to the stepper motor. Each pulse on the Step line causes the
RIW head to move one track in or out, depending on the state of the Direction Select line. Multiple-
track accessing is accomplished by repeated pulsing of the Step line until the desired track has been
reached. Seeking cannot occur while a Write operation is in progress.
4.1.5
READ/WRITE HEAD
The Model FDD100-5 Disk Drive uses a unique single-sided read/write head assembly that is mounted
on the head carriage. The head is fixed with respect to the carriage and diskette surface. The head is
basically a ferrite core that is mounted in a ceramic button assembly, the face of which has a spherical
profile. The head also uses a trailing tunnel-erase structure.
4.1.6
SENSORS AND SWITCHES
The index sensor is a light-sensitive device which is activated whenever an index or sector hole
passes it in rotation. The sensor output is a pulse which is fed back to the interface as the Index/
Sector signal. The Track
0llJ
signal is generated when the RIW head carriage trips a microswitch as it
reaches track
00
on the diskette. The Track
l l J l l J
signal is then transmitted back to the interface. The
Write Protect sensor detects the presence or absence of a notch in the diskette envelope. If a tab is
covering the notch (to indicate a Read-only diskette), a Write Protect signal is sent back to the
interface. The Write Protect signal also disables the Write logic so that writing on the diskette is not
possible.
4-3
Advertisement
Table of Contents
