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Note:
For drives which do not require Reduced Write Current
and/or Write Precompensation, the user should set these
cylinder values to the number of data cylinders plus 1.
The Landing Zone position is used with the START/STOP command to
indicate the direction and number of cylinders from the last, or
first, cylinders to the desired shipping or stopped position.
The most significant bit indicates the direction.
AO indicates
the landing zone is beyond the maximum cylinder,
as I indicates
it is before track 0.
The other 7 bits indicate the number of
cylinders in the desired direction the head will stop.
The Step Pulse Rate specifies the timing of seek steps.
The
three options are:
00
=
Non-Buffered Seek (3.0 ms/step)
01
=
Buffered Seek (28 us/step)
02
=
Buffered Seek (12 us/step).
The Drive Parameter List for hard-sectored or removable drives
must begin with a
List Format Code of 02 and contains two
additional bytes.
This parameter list must be sent if the E-F or
G-H jumpers are installed (indicating hard-sectored drives).
The Drive Type Code indicates the characteristics of the drive,
defined as:
Bits
Bit
2
Bit 3
Bits
This
units
0-1
=
0
=
0
=
1
=
0
=
1
4-7
=
0
command
for the
Must be 0
Soft-sectored
Hard-sectored
Removable media drive
Fixed Media Drive
Must be 0.
is used to reserve logical units or extents within
use of an Initiator.
The Reservation function is used to prohibit certain kinds of
access from some Initiators so that the reserving Initiator can
complete multi-step transactions without
interference.
Extra
drives are also implicitly reserved to the active initiator
during an active chain of linked commands.
An Initiator may only
have one reservation per logical unit.
Reserve Unit:
If the Extent bit (Bit 0 of Byte 01)
is zero,
and no extent
within the unit is currently reserved by another Initiator, then
this command shall cause the unit to be reserved for exclusive
use of the Initiator until the reservation is released by a
RELEASE UNIT command issued by the same Initiator or by a BUS
DEVICE RESET message from any Initiator or a "Hard" RESET
condi-
tion.
It is permissible for an Initiator to reserve a logical
unit that is currently reserved for that Initiator.
The Reserva-
tion Identification (Byte 02) and the Extent List Length (Bytes
500504-00
6-36
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