BASF 6106 - Ready Oetection

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2.2.7.2 READY DETECTION
The ready detector (Fig. 2-25) is used to
monitor the
INDEX pulses for the rotational
speed of the disko The INDEX pulses are input
to the 300 msec hold-over-one shot. When the
time
between two consecutive INDEX pulses
is greater than 300 msec, the index counter
is held reset. If the time is less than
300 msec, the hold-over-one shot is held fired and
enables the index counter. When three consecutive
INDEX pulses have clocked the index counter, SPEED
is high and the READY/ signal is sent to the host
system (see
Timing Diagram Fig. 2-26).
FROH INPUT IXTERFACE ~I..:.../O.::....::E:.:.N..:...A~ ___ --,
FROH
INDEX
DETECTOR
INDEX
300 IDSec
O~"E SHOT
DIDEX COUNTER
A
A
FROH DC- CONTROL .-----_-'
INDEX
300 msec- OS
FFA
SPEED
READY
I
lOO .. ce;
FIGURE 2 - 25 READY DETECTOR
FIGURE 2 - 26 READY TIMING
2 - 19
HOST
SYSTEM
.... __ -.::;SP:,.:E:.:;E::;D ..
TO
THE ACTlVITY LED AND
DOOR LOCK DRIVER
SPEED
L----=I.",ND;;E~X;.:::;.O .. tr'o THE HEAD LOAD CIRCUIT