Adaptec 1520A User Guide - Page 30

SCSI Termination, Synchronous, Negotiation, Interrupt Channel

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AHA-1510A/20A Series User's Guide SCSI Termination The default termination setting AHA-1510A/20A Series host adapters is enabled. Disable termination for the host adapter if you attach SCSI devices to both the internal and external connectors. For more information on host adapter termination, see Terminating the SCSI Bus on page 3-2. Synchronous Negotiation Synchronous negotiation is a SCSI feature that allows the SCSI host adapter and its attached SCSI devices to transfer data in synchronous mode. Synchronous data transfer is faster than asynchronous data transfer. The Initiate Synchronous Negotiation setting determines whether the host adapter initiates synchronous negotiation with the SCSI device. At the default setting, yes, the host adapter initiates synchronous negotiation with the SCSI device. If you change the setting to no, the host adapter does not initiate synchronous negotiation; however, the host adapter always responds to synchronous negotiation if the SCSI device initiates it. If neither the host adapter nor the SCSI device negotiates for synchronous data transfers, data is transferred in asynchronous mode.You should normally leave the default setting because most SCSI devices support synchronous negotiation and because it allows for faster data transfer. Some older SCSI-1 devices do not support synchronous negotiation. This may cause your computer to operate erratically or hang if Initiate Synchronous Negotiation is enabled. Set Initiate Synchronous Negotiation to no for these devices. Interrupt Channel Host adapters and other option cards in your computer may not share IRQ settings. If you are installing two SCSI host adapters, make sure they each have unique IRQ settings. s The same IRQ channel must be selected on both jumper blocks J6 and J9. s Note that some operating systems may not run properly if you assign IRQ 9 to the host adapter. 2-10 AAAAAAAAAAAAAAAAAASPCAAAAAArtuHoiAAArncAAAArtkAAAe-SAAAn1NAAApt5AAAeuD1AAAcmAAA0aAAANtAbeAAAeu:/AAAr2mAAA1:0AAA15bAAAA/1eAAA1rAAA0S8:AAA4/e4AAA90rAAA94i0eAAA1-AAAs08AAAU04AAA,2AAAsR-AAAe0AAAre0'AAAvsAAA.AAAGCAAAuAAAAAAidAAAeAAAAAAAAAEAAACAAAAAANAAAAAADAAAAAAaAAAtAAAePAAA: aAAA1gAAA1AAAe/AAA:2AAA29AAA-/AAA91AAA40AAAAAAAAAAAAAAAAAAAA

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2-10
AHA-1510A/20A Series User’s Guide
AHA-1510A/20A Series User’s Guide
Stock Number: 510400-00, Rev. C
Page: 2-10
Print Spec Number: 491842-00
Current Date: 11/18/94
ECN Date: 11/29/94
SCSI Termination
The default termination setting AHA-1510A/20A Series host adapters
is
enabled
. Disable termination for the host adapter if you attach SCSI
devices to
both
the internal and external connectors. For more infor-
mation on host adapter termination, see
Terminating the SCSI Bus
on
page 3-2.
Synchronous
Negotiation
Synchronous negotiation
is a SCSI feature that allows the SCSI host
adapter and its attached SCSI devices to transfer data in synchro-
nous mode. Synchronous data transfer is faster than asynchronous
data transfer.
The Initiate Synchronous Negotiation setting determines whether
the host adapter initiates synchronous negotiation with the SCSI
device. At the default setting,
yes
, the host adapter initiates synchro-
nous negotiation with the SCSI device. If you change the setting to
no,
the host adapter does not initiate synchronous negotiation; how-
ever, the host adapter always responds to synchronous negotiation if
the SCSI device initiates it. If neither the host adapter nor the SCSI
device negotiates for synchronous data transfers, data is transferred
in asynchronous mode.You should normally leave the default set-
ting because most SCSI devices support synchronous negotiation
and because it allows for faster data transfer.
Some older SCSI-1 devices do not support synchronous negotiation.
This may cause your computer to operate erratically or hang if Ini-
tiate Synchronous Negotiation is enabled. Set Initiate Synchronous
Negotiation to
no
for these devices.
Interrupt Channel
Host adapters and other option cards in your computer may not
share IRQ settings. If you are installing two SCSI host adapters,
make sure they each have unique IRQ settings.
■
The same IRQ channel must be selected on both jumper blocks
J6 and J9.
■
Note that some operating systems may not run properly if you
assign IRQ 9 to the host adapter.