82091AA Datasheet, PDF (158/204 Pages) Intel Corporation – ADVANCED INTEGRATED PERIPHERAL (AIP)

82091AA
tween Conventional and Perpendicular drives are al-
lowed without having to issue PERPENDICULAR
MODE Commands between the accesses of the two
different drives nor having to change write precom-
pensation values
With this command the length of the Gap2 field and
VCO enable timing can be altered to accommodate
the unique requirements of these drives Table 36
describes the effects of the WGATE and GAP bits
for the PERPENDICULAR MODE Command
Software and Hardware reset have the following ef-
fects on the enhanced PERPENDICULAR MODE
Command
1 A software reset (Reset via DOR or DSR regis-
ters) only sets GAP and WGATE bits to 0
D0 and D1 retain their previously programmed
values
2 A hardware reset (Reset via pin 32) sets all bits
(GAP Wgate D0 and D1) to 0 (All Drives Con-
ventional Mode)
When both GAP and WGATE equal 0 the PERPEN-
DICULAR MODE Command will have the following
effect on the FDC
1 If any of the new bits D0 and D1 are pro-
grammed to 1 the corresponding drive is auto-
matically programmed for Perpendicular mode
(ie GAP2 being written during a write operation
the programmed Data Rate will determine the
length of GAP2) and data will be written with 0
ns write precompensation
2 Any of the new bits (DO D1) are programmed for
0 the designated drive is programmed for Con-
ventional Mode and data will be written with the
currently programmed write precompensation
value
3 Bits D0 and D1 can only be over-written when
the OW bit is 1 The status of these bits can be
determined by interpreting the eighth result byte
of the DUMPREG Command (Note if either
the GAP or WGATE bit is 1 bits D0 and D1 are
ignored )
8 5 3 13 POWERDOWN MODE Command
The POWERDOWN MODE Command allows the
automatic power management and enables the en-
hanced registers (EREG EN) of the FDC The use of
the command can extend the battery life in portable
PC applications To enable auto powerdown the
command may be issued during the BIOS power on
self test (POST)
This command includes the ability to configure the
FDC into the enhanced mode extending the SRB
and TDR registers These extended registers ac-
commodate bits that give more information about
floppy drive interface allow for boot drive selection
and identify the values of the PD and IDLE status
As soon as the command is enabled a 10 ms or a
0 5 sec minimum powerup timer is initiated depend-
ing on whether the MIN DLY bit is set to 0 or 1 This
timer is one of the required conditions that has to be
satisfied before the FDC will enter auto powerdown
Table 36 Effects of WGATE and GAP Bits
GAP WGATE
MODE
VCO Low
Time after
Index Pulse
Length of
Gap2 Format
Field
Portion of
Gap2
Written by
Write Data
Gap2 VCO
Low Time for
Read
Operations
Operation
0
0 Conventional Mode
33 Bytes
22 Bytes
0 Bytes 24 Bytes
0
1 Perpendicular Mode
33 Bytes
22 Bytes 19 Bytes 24 Bytes
(500 Kbps and Lower Data Rates)
1
0 Reserved (Conventional)
33 Bytes
22 Bytes
0 Bytes 24 Bytes
1
1 Perpendicular Mode
(1 Mbps Data Rate)
18 Bytes
41 Bytes 38 Bytes 43 Bytes
NOTE
When either GAP or WGATE bit is set the current value of precompensation in the DSR is used
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