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Installing the A5150A Adapter
SCSI Bus Termination
Chapter 230
The A5150A is supported on the A400, A500, L-Class, and N-Class
HP 9000 systems.
Bus Termination
The SCSI bus must be properly terminated. The first and last physical
SCSI devices on the ends of the SCSI bus must be terminated either by
physical terminators or auto termination. The terminators of all other
SCSI devices on the bus must be removed or disabled. Note that the
A5150A HBA is also on the bus. However, because the A5150A HBA
contains an automatic termination feature, external terminators on the
HBA are not usually required. (Terminators are not shipped with the
A5150A; you can order them separately, if needed.) The A5150A provides
automatic termination when a SCSI cable from a powered SCSI device (a
peripheral or other HBA) is connected to either the internal or external
connector of the A5150A. Some exceptions where external terminators
are required are described in “When and How to Turn Off Auto
Termination” on page 31.
The older A5150A HBA (A5150-60001) has two sets of pins that control
enabling and disabling (defeating) the auto termination feature. The
pins—labeled A_TERM and B_TERM—are at the end of the HBA that is
opposite the bulkhead connectors. A_TERM controls the auto
termination feature for channel A, and B_TERM controls the feature for
channel B.
NOTE The A5150A’s auto termination feature cannot be set independently for
the internal and external connectors of the HBA.
Table 2-3 Auto Termination PDC Versions
HP 9000 System PDC Version
A400 and A500 40.20 or later
L-Class 39.40 or later
N-Class 39.41 or later