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参数资料
| 型号： | 37C67X |
| 厂商： | SMSC Corporation |
| 英文描述： | ENHANCED SUPER I/O CONTROLLER WITH FAST IR |
| 中文描述： | 增强的超级I / O控制器，快速红外线 |
| 文件页数： | 156/194页 |
| 文件大小： | 546K |
| 代理商： | 37C67X |
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64
with a single Relative Seek command is 255
(D).
The internal register, PCN, will overflow as the
cylinder number crosses track 255 and will
contain 39 (D). The resulting PCN value is thus
(RCN + PCN) mod 256. Functionally, the FDC
starts counting from 0 again as the track
number goes above 255 (D).
It is the user's
responsibility to compensate FDC functions
(precompensation
track
number)
when
accessing tracks greater than 255. The FDC
does not keep track that it is working in an
"extended track area" (greater than 255). Any
command issued will use the current PCN value
except for the Recalibrate command, which only
looks for the TRACK0 signal.
Recalibrate will
return an error if the head is farther than 79 due
to its limitation of issuing a maximum of 80 step
pulses. The user simply needs to issue a second
Recalibrate command. The Seek command and
implied seeks will function correctly within the
44 (D) track (299-255) area of the "extended
track area". It is the user's responsibility not to
issue a new track position that will exceed the
maximum track that is present in the extended
area.
To return to the standard floppy range (0-255) of
tracks, a Relative Seek should be issued to
cross the track 255 boundary.
A Relative Seek can be used instead of the
normal Seek, but the host is required to
calculate the difference between the current
head
location
and
the
new
(target)
head
location. This may require the host to issue a
Read ID command to ensure that the head is
physically on the track that software assumes it
to be.
Different FDC commands will return
different cylinder results which may be difficult
to keep track of with software without the Read
ID command.
Perpendicular Mode
The Perpendicular Mode command should be
issued prior to executing Read/Write/Format
commands that access a disk drive with
perpendicular recording capability.
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
30 describes the effects of the WGATE and
GAP bits for the Perpendicular Mode command.
Upon a reset, the FDC will default to the
conventional mode (WGATE = 0, GAP = 0).
Selection
of
the
500
Kbps
and
1
Mbps
perpendicular modes is independent of the
actual data rate selected in the Data Rate Select
Register. The user must ensure that these two
data rates remain consistent.
The Gap2 and VCO timing requirements for
perpendicular recording type drives are dictated
by the design of the read/write head.
In the
design of this head, a pre-erase head precedes
the normal read/write head by a distance of 200
micrometers. This works out to about 38 bytes
at a 1 Mbps recording density. Whenever the
write head is enabled by the Write Gate signal,
the pre-erase head is also activated at the same
time. Thus, when the write head is initially
turned on, flux transitions recorded on the media
for the first 38 bytes will not be preconditioned
with the pre-erase head since it has not yet been
activated. To accommodate this head activation
and
deactivation
time,
the
Gap2
field
is
expanded to a length of 41 bytes. The format
field shown on Page 57 illustrates the change in
the Gap2 field size for the perpendicular format.
相关PDF资料 |
PDF描述 |
|---|---|
| 37C957FR | ULTRA I/O CONTROLLER FOR PORTABLE APPLICATIONS |
| 37FMA1-ABW31N | SPECIAL SWITCH-PIEZO SWITCH, SPST, MOMENTARY, 0.2A, 24VDC, PANEL MOUNT-THREADED |
| 37FML1-BEW31N | SPECIAL SWITCH-PIEZO SWITCH, SPST, MOMENTARY, 0.2A, 24VDC, PANEL MOUNT-THREADED |
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相关代理商/技术参数 |
参数描述 |
|---|---|
| 37C-6BH-5-5 | 制造商:Birtcher Products 功能描述: |
| 37C72U-185 | 制造商:White-Rodgers 功能描述: |
| 37C73U-170 | 制造商:White-Rodgers 功能描述: |
| 37C73U-171 | 制造商:White-Rodgers 功能描述: |
| 37C922BQFP | 制造商:SMSC 功能描述: |
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