2.2.6 SCSI 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 SYM8953U host adapter is also on the SCSI
Important: To utilize Ultra2 SCSI performance, you must only have LVD devices on the bus. Do not mix any SE devices with LVD devices or the entire bus will drop to SE, limiting bus performance to Ultra SCSI levels.
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 type/setting for each device and how to set/change it.
Caution: The autoenable/disable sensing feature on the SYM8953U may enable termination erroneously if it is directly cabled to another SCSI device or host adapter using the same sensing method. The SYM8953U senses the presence of SCSI devices by detecting the ground signal on conductor 50 of the SCSI cable.
The SYM8953U automatically controls SCSI bus termination for three different bus configurations, depending on how it is connected (see Figure 2.1). The three bus configurations are:
•Section 2.2.6.1, “Internal Bus Connections”
•Section 2.2.6.2, “External Bus Connections”
•Section 2.2.6.3, “Internal and External Bus Connections”
Termination on the SYM8953U host adapter for these three different bus configurations is discussed below.
Installing the SYM8953U Host Adapter |
