Differentiai Read Filter: Test Points 1 And; Track 0 Sensor: Ic 3B, Pin; Index Sensor: Test Point 9; Figure 31: Index Sensor - Seagate ST212 Product Manual

9.1.1 DIFFERENTIAL READ FILTER: TEST POINTS 1 AND 2
These points may be used to moinitor Differential Read Data. The typical am-
plitude of the signal resulting from adding the two channels is 160 mVolts. This
signal is observedat Cylinder Zero, head 0 or 1. A full track record of high fre-
quency data (0000 or 1111) will typically resemble Figure 30.
FIGURE 30:
DifferentiaI Read Filter
9.1.2 TRACK 0 SENSOR: IC 38, PIN 1
IC 3B, pin 1 may be used to monitor the Track 0 sensor. A high logic level indi-
cates valid Track 0. The microprocessor requires the stepper motor to he at phase
A and the Read/Write heads to be at Cylinder Zero before it will output a valid
Thlck
0
signal.
9.1.3 INDEX SENSOR: TEST POINT 9
lest point 9 may be used to monitor the Index sensor. Only the leading edge
of the pulse is valid. A typical signal will resemble Figure 31.
16.67 msec. ±1%
1.3 msec. typical-_-I
FIGURE 31:
Index Sensor
34
ST212 PRODUCT MANUALIRev. B