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Copyright © 2000 Toshiba corporation. All rights reserved.
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10.12 Reset
A RESET condition sets the drive ( or both drives in case of Master/Slave connection ) BSY, allowing the
drive to perform the specified initialization required for normal operation.
A RESET condition can be generated by both hardware and software. There are two hardware resets, one
is by the Host (- RESET) and the other is by the drive power sense circuitry. These resets are set high
when the system and the drive respectively acknowledge specified supply voltage ( See 6.1).
The other reset is software generated. The Host can write to the Device Control register and set the
reset bit. The host software condition will continue until the reset bit is set to zero.
.
Once the reset is negated and the drive is re-enabled, with BSY still active, the drive will perform
necessary hardware initialization, clear any previously programmed drive parameters and revert
to the defaults, load the Task File registers with their initial values, and then clear BSY. No interrupt
is generated when initialization is complete. The initial values ( hex ) for the Task File registers are
as follows.
Table 10.12-1 Initialization of Task File registers
REGISTER POWER ON HARDWARE RESET SOFTWARE RESET
Data 00 00 00
Error 01 01 01
Sector Count 01 01 01
Sector Number 01 01 01
Cylinder Low 00 00 00
Cylinder High 00 00 00
Device/Head Register 00 00 00
Status/Alternate Status 50 or 52 50 or 52 50 or 52
Device address
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7E or FE 7E or FE 7E or FE
ECC Length 4 bytes 4 bytes no change(*1)
Data Buffer undefined undefined no change
Addressing mode default default no change
Auto stand-by mode disable disable no change
Read Cache enable enable no change (*1)
Write Cache
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enable enable no change (*1)
Multiple mode 16 sectors 16 sectors no change (*1)
DMA transfer mode Multiword
DMA mode 2
Multiword DMA mode
2
no change(*1)
PIO transfer mode PIO mode 4
flow control
PIO mode 4 flow
control
no change(*1)
(*1): Software reset settings are affected by set feature command.
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ATA-2 Notes: This register is obsolete. It is recommended that a device not respond to a read of this address. If a
device does respond, it shall be sure not to drive the DD7 signal to prevent possible conflict with floppy disk
implementations.
The drive supports this register to maintain compatibility for ATA-1.
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ATA-2 Notes: The default mode for write cache is “disable” after ATA-2. This is violation of ATA-2 specification. This setting can be
changed by factory.