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3.4.4
PARITY ENABLE
The installation of the PAR jumper will cause the ACB-5500 to
c he c k for bus
0
u t (d a t a i n t o t h e A C B - 5500) par i t y err
0
r s •
Th i s
jumper should only be installed if all SCSI devices communicating
with the ACB-5500 generate SCSI data parity.
The ACB-5500 will
always generate parity on bus in data.
3.4.5
SCSI BUS ADDRESS
The installation of jumper A4,
A2,
and Al set the SCSI bus
address for the ACB-5500.
SCSI devices can have an address of 0
to 7 but no two devices can have the same address.
3.5
POWERING-ON THE ACB-5500
Once the ACB-5500 is properly configured,
the controller may be
powered on.
When power is supplied to the system, the controller
will enter a power-up mode and wait for a maximum of 18 seconds
for the drive to become ready.
During the l8-second power-on
sequence, the controller performs a self test and begins checking
for drive 0, 1, 2, and 3 to become ready.
If the host sends a
command requiring access to a drive before it has become ready
(and before
18
seconds have elapsed) the controller will accept
the command and cont i nue to check for a ready s ta tus.
Once the
drive comes ready, the controller will then execute the command;
if
18
seconds elapse, and the drive does not come ready, a DRIVE
NOT READY (04 H ) error will result.
The controller will then
check for a ready status on the next command requiring access to
that drive.
Once a drive comes ready, the controller will recalibrate the
head to track 0.
If the drive started at track 0, the controller
will step the head off of track 0 to confirm that the drive can
seek and that the track 0 signal was valid.
With the drive's
ability to seek confirmed, the controller then seeks back to
t r a c k 0.
Th e d r i ve act u a tor
(i
f i t can be see n) a pp ear s tom a k e
a short 'bl ip. '
The controller then attempts to read from track 0, parameter
information, which is written during formatting.
If the drive is
unformatted,
or had been formatted by other than an Adaptec
c on t roll e r ,
the par am e t e r
i n for mat ion
i s
not pre sen t •
Th e
controller
then sets "blown format" to warn the user that the
drive is unusable,
the reset sequence is stopped and the
controller is ready for a command.
The drive must be formatted
to allow a READ or WRITE access to disk data.
If the drive is correctly formatted, the controller will seek the
drive to the last cylinder and read the largest block address
present.
The parameter information and largest block addresses
are saved by the ACB-5500.
500504-00
3-5
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