Appeal No. 2000-1259
Application 08/815,894
sequence associated with a trellis, with the result that the
output of the sequence detector is delayed by the length of this
buffer. Id. at 3. Prior-art read channels wait for the sequence
detector to finish processing a current sector before changing
the loop coefficients of the gain control, timing recovery, and
DC offset circuits, thereby necessitating that the sectors be
separated by a physical gap which is long enough to account for
the latency in the sequence detector:
Before the read channel can process a new user or
servo data sector, components such as the filters in
timing recovery, gain control, and DC offset control
must be reconfigured to acquire the preamble of the new
sector. During this reconfiguration process, the
magnetic disk continues to spin under the read head[,]
creating [the need for] a physical gap on the medium
between the end of a current sector and the beginning
of a new sector.
Specification at 21, l. 22 to p. 22, l. 4. Appellants' sampled
amplitude read channel, shown in Figure 3, reduces the size of
the required gap by using the following pipelining technique:
In order to reduce the gap between sectors, operation
of the read channel is pipelined by reconfiguring the
gain control 50, timing recovery 28, the DC offset 1
circuits before the discrete time equalizing filter 26
and sequence detector 34 have finished processing the
samples for the current sector. This allows the read
channel to begin acquiring the preamble (68,5) of a
next sector (user or servo data) concurrent with
processing the end of the previous sector, thereby
decreasing the [required] physical gap on the medium
between sectors.
Id. at 22, ll. 4-12.
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