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3.1
INTRODUCTION
SECTION 3
APPLICATIONS
The Q20S0 drive will be incorporated into a number of different systems. Each of these applications will vary
depending on system design, software, drive controller, cabinet design, etc. Quantum intends to assist engineers
working with the Q20S0 by supplying accurate technical data on the drive. This section of the Q20S0 Technical
Manual provides information on those aspects of the Q20S0 that influence the integration of the drive into a system.
Specific topics include the interface, errors and media defects, self diagnostics, and track formats.
3.2
POWER ON RECALmRATION SEQUENCE
The following summarizes the recalibration procedure that the Q20S0 performs when power to the drive is turned
on.
1. Initialize all registers.
2. Check index time.
3. Delay 2 seconds.
4. Calibrate PI and P2 ("circle" size.)
a) Find PI and P2 maximum and minimum.
b) Compute PI and P2 center value.
5. Servos.
6.
Generate rough calculations of "NULL 1" value (to negate stiffness of wires on the head stack).
7.
Do 100-5 track seeks to the center of the disk track area (5 track seeks equal single step mode.)
S. Wait 1 second to calculate a new "NULL 1" value.
9. Find track 0 (uses single step seeks).
10. Settle and look at track 0 bursts.
(If
fifth servo burst equals zero amplitude, then track 0 has been detected.)
11. Compare servo burst values for average amplitude.
12. Compare results (track 0 detect) to the track counter.
13. If error, drop actuator power and try again.
3.3
INTERFACE
The Q20S0 uses a SAIOOO compatible drive interface with a 4.34 Mbitlsec transfer rate. General interface tim-
ing specifications can be found in the Q2080 Product Description OEM Manual. Also, refer to section 1.3.9 and
1.3.15 of this manual for additional interface information.
When the drive receives more STEP pulses than there are cylinders on the disk and the direction of seek is out
(toward disk OD), the heads will seek to track O. Then the drive sends SEEK COMPLETE and asserts READY.
3.4
ERRORS AND MEDIA DEFECTS
3.4.1 ERRORS
Any discrepancy between recorded data and recovered data is defined as an error. High density digital record-
ing systems require an error detection and correction scheme to enhance the operational performance and increase
the reliability of the system. Disk storage systems record data in a precisely timed bit stream. Data recovery is ac-
complished with a data separator that uses this precise bit positioning to detect encoded data bits.
In these systems three types of errors occur, drop outs, drop ins, and phase shifts, with the most predominant
error pattern being a burst of errors occuring in one or more data tracks.
A drop in is when the system sees a bit when it was not expecting to see one. This is caused by a media flow caus-
ing a rise in signal amplitude. A drop out is a bit that has shifted from its nominal position further than the data
separator can tolerate due to signal amplitude decrease. Phase shift detects are small shifts in the data signal that the
data separator cannot tolerate but have little or no effect on the signal amplitude.
3-1
REV A (01/84)
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