Specifications

1.3.2 Drive Mechanism
The Head Positioning Actuator moves the read/write head{s} to the desired track on the diskette. The head{s} is
loaded onto the diskette when the door knob is closed. If no diskette is inserted when the door knob is closed, the
heads will not touch each other.
The dc drive motor under phase locked loop speed control (using an integral tachometer) rotates the spindle at 360
rpm. A contracting collet/spindle assembly provides precision media positioning and clamping to ensure data inter-
change. A diskette ejector places the diskette within reach of the operator when the diskette
is unclamped.
1.3.3 Positioning Mechanism
The read/write head assembly is accurately positioned through the use of a precision HeliCam V-groove lead
screw with a flat nut follower which
is attached to the head carriage assembly. Precise track location is accomplished
as the lead screw
is rotated in discrete increments by a stepper motor.
1.3.4 Read/Write Heads
The proprietary head {s} is a single element ceramic read/ write head with straddle erase elements to provide erased
areas between data tracks. Thus, normal interchange tolerances between media
and drives will not degrade the
signal to noise ratio
and diskette interchangeability is ensured.
The read/write head{s) is mounted on a carriage which is located on precision carriage ways. The diskette is held in
a plane perpendicular to the read/write head (s) by a platen located on the base casting. This precise registration
assures perfect compliance with
the read/write head{s}. The read/write head{s} is in direct contact with the
diskette. The
head surfaces have been designed to obtain maximum signal transfer to and from the magnetic sur-
face of the diskette with minimum
head/diskette wear due to the low mass suspension system.
1.3.5 Recording Formats
The format of the data recorded on the diskette is totally a function of the host system. This format can be designed
around the user's application to take maximum advantage of the total available bits that can be written on anyone
track.
Figure 1-2 provides a functional diagram of the
SA810/860. For a detailed discussion of the various recording for-
mats, refer to Section
VI.
1.4 FUNCTIONAL OPERATIONS
1.4.1 Power Sequencing
Applying dc power to the SA810 or SA860 can be done in any sequence; however, during power up, the WRITE
"GATE line must be held inactive or at a high level. After application of dc power, a 90 ms delay should be introduc-
ed before a seek operation or before the control output signals are valid. After powering on, the initial position of
the read/write heads with respect to the data tracks on the media is indeterminant. In order to assure proper posi-
tioning of the read/write
heads after power on and internal write current SWitching at the proper track, a STEP
OUT operation should be performed until the TRACK 00 line becomes active (recalibrate).
1.4.2 Drive Selection
Drive selection occurs when the DRIVE SELECT line in the drive is activated. Only the drive with this line active
will respond to input lines or gate output lines. Under normal operation, the DRIVE SELECT line enables the input
and output lines, starts the spindle motor, locks the door, and lights the Activity LED on the front of the drive.
1.4.3 Motor On
In order for the host system to read or write data, the dc drive motor must be turned on. In the standard configura-
tion, this
is accomplished by activating the line DRIVE SELECT. A 165 ms delay must be introduced after ac-
tivating this line (or the
TRUE READY line may be monitored) to allow the motor to come up to speed before
reading
or writing can be accomplished. All motors in a daisy chain configuration can be turned on with the op-
tional
MOTOR ON line or the spindle motor may be activated when both MOTOR ON and DRIVE SELECT are
present. Refer to paragraphs
7.8 and 7.9.
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