~.:!I.~
i1UFFERED SEEK
The ST22S mlY be configured \(j the RECOVERY MODE oplion by
shorting pill! ] IInd ~ II J1. This oplion enables Ihe ReJlcI/W~ilelIeacis
to mierostep. This ~epositionini oplion mlY be used lifter Ihe conlroller
has completed ill retry oplions on a read error.
RECOVERY MODE is initialed by the controller assenini die
RECOVERY MODE line low (Irue) at Ihe interface. This changes the
STEP line to
II microslep function aRev iOOnsec. A Step pulse will
now cause SEEK COMPLETE to go false IOOnsec after the drive
Il'e-
ceives the pulse. The drive then microsteJl' olf-tl1lck using the op-
timum algorithm. dlowing 8mSIeCfor the heads to settle, and then
takes the SEEK COMPLETE line true.
The controller may then allempt to read data. If data is not read
com:ctly, the coniroller malY issue Iin additionall Step pulse. Up to
eight scparIte micros\ep algorithms may be: accessed before the se-
quence is repeated.
When data is read correctly, the controller exits RECOVERY MODE
by taking the RECOVERY MODE line false ai the interface. The
drive then returns the heads to the nominal position
by taking SEEK
COMPLETE false. waiting 8mscc for the heads to settle and reassert-
ing SEEK COMPLETE.
Note:
AU writing is inhibited while the RECOVERY MODE signal is
irUc.
To minimize access time. pubes may be issued at an accelerated rate
and buffered in a counter. Initiation of a seek starts immediately after
the lint pulse is m:aved. Head motion occun durinS pulse accumula-
tion. and \he seek is completed followina r=:ipt of all pulses.
- DIRECTIONIN
I~'!~E//A STABLE V///t~nCARF,I////
1__ -11- -I ~ -11-1__
~1J
1_1yp.-:-l~r--I I-~':..
-SEEK COMPlETE Ib- L
1__ -""9·1
--f . ----1 .__ .-1
---DA-ove-SEl£-CT-1 . I
"Tme II !rom ~ 01 heed _ 10 SEEK COMPlETE.
4.3.2 SLOW-STEP(Treck-to-Treck)
In single-track Slow-Step mode. the Read/Write heads move at the
rate of the incomina Step pulses. The minimum pulse period is
3mscc. The stepper motor is sellied and SEEK COMPLETE is issued
20mscc max. after the leadina edge of the last pulse.
- DAN! SEl£1 ,
-Ir'_...·-11-'__ .
- DIRECTIONINI
~OON'T:cAAEi'A V/////////tOON'T ~REI/////////
-STEI' -11-'__ :-:11-'-_.
~1J I'
._,.-I-t-':~~~----l
- SEEK COMPlETE I L-
18
FIGURE 14:
Buffered-Seek Timing
FIGURE 15:
Slow-Step Timing
ST11' OEMIR,.. i'
~
,J)
t.
t.
Q"••
RECOVERY MODE 3J.i'!J
$111' OEM/« ••. F IS
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