Access Time Definition And Timing; Step Pulse Period And Seek Method; Figure 5. Buffered-Seek Timing; Figure 6. Auto-Truncation Timing - Seagate ST251 Product Manual

1.2 ACCESS TIME DEFINITION AND TIMING
FIGURE
5:
Buffered-Seek Timing
1.3 STEP PULSE PERIOD AND SEEK METHOD
Access time is defined as the time from the leading edge of the first
step pulse received to Seek Complete (including settling). All seek
ti mes are true statistical averages and are calculated with a step pulse
period of 10 jJsec. at nominal power and temperature.
- DIRECTION IN
-1 ~
100
nsec. min.
-STEP
-1 ~
r-,
3 ~sec. min.
100
nsec. typo
200
~sec. max.
. .
. ,
- SEEK COMPLETE :
I L
~DON'T CARE~A STABLE ~DON'T CARE~
2
~sec. min.
~ L
1 0
~sec. max.
100
nsec min.
_11_
-I ~
(
b
(
8 msec. max.
40 msec. max.
95 msec, max,
8.33 msec.
Track-to-Track:
Average:
Full-Stroke:
Average Latency:
- DRIVE SELECT
I :
I
I.•
40 msec. avg.
~I
95
msec. max.
The step signal is a 2jJsec. minimum width pulse which initiates read/
write head motion. The step pulse period determines the access
method. The number of pulses determines the seek length. The step
pulse period must be between 3 jJsec. and 200 jJsec.
Step pulses may be lost at periods greater than 200jJsec. For additional
information on step pulses and seek methods consult the Seagate
ST412 Interface Manual,
(
"
(
100
nsec. min-1 ~ 100 nsec. min-1 ~
FIGURE
6:
Auto- Truncation Timing
- TRACK
eJ
:. Excessive Step Pulses Recognized
,
: rr. _
: )) 1 --
·11
!<
- SEEK
COMPLETE
9 msec. typo
I ••
~I
: ;;_r I _
(
(
I••
13 sec. max.
~I
1-2
ST251/251 R/277R Product Manual, Rev.A
ST251/251R/277R Product Manual, Rev.A
1-15