IBM PCI SCSI-2 Fast/Wide Single-Ended Adapter, Installation Manual

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Appendix C. Jumper Settings and Multi-Adapter
Configurations
Jumper Settings and Multi-Adapter Configurations
The PCI SCSI-2 Fast/Wide Single-Ended Adapter contains built-in SCSI terminators.
The adapter determines if it is in the middle of the SCSI chain or at the end of the
chain and enables or disables the built-in terminators as required. This is
accomplished by determining which, if any, cables are attached to the adapter.
Jumper Block J7:
The default configuration for the adapter places all the jumper
settings to OUT and is how the adapter is shipped. This configuration is for a single
adapter on a SCSI chain allowing the adapter to sense where it is in the chain, in the
middle or on the end. The adapter enables or disables its built-in SCSI terminator as
required.
Typical installations use only one adapter with some internal or external SCSI
devices. In these cases, the jumpers are left in the factory position.
Multi-Adapter Configurations:
Using more than one SCSI adapter on any
single SCSI bus may require the automatic termination sensing logic to be
overridden by setting the individual jumpers on jumper block J7.
The automatic sensing logic that controls the enablement and disablement of the
built-in terminators detects external and internal terminators on the external and
internal SCSI bus. This control logic cannot sense other built-in terminators of
another adapter on the SCSI bus. For those instances, you must tell the adapters
that the external cabling is in use by moving the jumpers on jumper block J7.
Switch Setting Definitions:
The various switch settings and cable attachments
can be combined in many different ways. The following switch setting definitions
explain how the terminators are affected:
S1 When placed in the OUT position, the termination control logic
automatically determines the attachment or non-attachment of an internal
narrow cable and terminator.
When placed in the IN position, the termination control logic indicates that
an internal narrow cable and terminator is attached.
S2 When placed in the OUT position, the termination control logic
automatically determines the attachment or non-attachment of an internal
wide SCSI cable and terminator.
Appendix C. Jumper Settings and Multi-Adapter Configurations
C-1