2.2.6SCSI Bus Termination
The devices making up the SCSI bus are connected serially (chained together) with SCSI cables. The first and last physical SCSI devices connected on the ends of the SCSI bus must have their terminators active. All other SCSI devices on the bus must have their terminators removed or disabled. Remember that the LSIU80ALVD is also on the SCSI
Important: To utilize Ultra2 SCSI performance, the user must only have LVD devices on the bus. Do not mix any SE devices with LVD devices as the entire bus will drop to SE with maximum Ultra SCSI performance.
The peripheral device terminators are usually set with jumpers, resistor modules, or with a switch on the peripheral. Refer to the peripheral manufacturer’s instructions and to the user’s manual for your computer for information on how to identify the terminator setting of each device and how to change it.
Caution: The autoenable/disable sensing feature on the LSIU80ALVD may enable termination erroneously if it is directly cabled to another SCSI device or host adapter using the same sensing method. The LSIU80ALVD senses the presence of SCSI devices by detecting the ground signal on conductor 50 of the SCSI cable.
The LSIU80ALVD automatically controls SCSI bus termination for three different bus configurations, depending on the use of connectors (see Figure 2.1). The three bus configurations are:
•Only for internal SCSI connections,
•Only for an external SCSI connection, and
•Connections to both internal and external SCSI connectors.
Termination on the LSIU80ALVD for these three different bus configurations is discussed below.
Installing the LSIU80ALVD |