When both GAP and WGATE bits of the
PERPENDICULAR MODE COMMAND are both
programmed to "0" (Conventional mode), then
D0, D1, D2, D3, and D4 can be programmed
independently to "1" for that drive to be set
automatically to Perpendicular mode. In this
mode the following set of conditions also apply:
1. The GAP2 written to a perpendicular drive
during a write operation will depend upon the
programmed data rate.
Note: Bits D0-D3 can only be overwritten when
OW is programmed as a "1".
If either GAP or WGATE is a "1" then
D0-D3 are ignored.
Software and hardware resets have the
following effect on the PERPENDICULAR
MODE COMMAND:
1. "Software" resets (via the DOR or DSR
registers) will only clear GAP and WGATE
bits to "0". D0-D3 are unaffected and retain
their previous value.
2. The write pre-compensation given to
perpendicular mode drive wil be 0ns.
a
3. For D0-D3 programmed to "0" for
conventional mode drives any data written
will be at the currently programmed write
pre-compensation.
2. "Hardware" resets will clear all bits (GAP,
WGATE and D0-D3) to "0", i.e all
conventional mode.
Table 29 - Effects of WGATE and GAP Bits
PORTION OF
GAP 2
LENGTH OF
WRITTEN BY
GAP2 FORMAT WRITE DATA
WGATE GAP
MODE
FIELD
OPERATION
0
0
0
1
Conventional
Perpendicular
(500 Kbps)
Reserved
(Conventional)
Perpendicular
(1 Mbps)
22 Bytes
22 Bytes
0 Bytes
19 Bytes
1
1
0
1
22 Bytes
41 Bytes
0 Bytes
38 Bytes
The LOCK command defines whether the
EFIFO, FIFOTHR, and PRETRK parameters of
the CONFIGURE command can be RESET by
the DOR and DSR registers. When the LOCK
bit is set to logic "1" all subsequent "software
RESETS by the DOR and DSR registers will not
change the previously set parameters to their
default values. All "hardware" RESET from the
RESET pin will set the LOCK bit to logic "0" and
return the EFIFO, FIFOTHR, and PRETRK to
LOCK
In order to protect systems with long DMA
latencies against older application software that
can disable the FIFO the LOCK Command has
been added. This command should only be
used by the FDC routines, and application
software should refrain from using it. If an
application calls for the FIFO to be disabled
then the CONFIGURE command should be
used.
69
SMSC [ SMSC CORPORATION ]
