FDC37C78-HT View Datasheet(PDF) - Microchip Technology
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Description
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FDC37C78-HT Datasheet PDF : 82 Pages
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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.
2. The write pre-compensation given to a
perpendicular mode drive wil be 0ns.
3. For D0-D3 programmed to "0" for conventional
mode drives any data written will be at the
currently programmed write pre-compensation.
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. "Hardware" resets will clear all bits ( GAP,
WGATE and D0-D3) to "0", i.e all conventional
mode.
WGATE
0
0
1
1
GAP
Table 29 - Effects of WGATE and GAP Bits
LENGTH OF
PORTION OF GAP 2
GAP2 FORMAT WRITTEN BY WRITE
MODE
FIELD
DATA OPERATION
0 Conventional
1 Perpendicular
(500 Kbps)
0 Reserved
(Conventional)
1 Perpendicular
(1 Mbps)
22 Bytes
22 Bytes
22 Bytes
41 Bytes
0 Bytes
19 Bytes
0 Bytes
38 Bytes
56
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