LSI U80ALVD - Manual (Page 17)

Interface Descriptions 1-5
1.3.3 Ultra2 SCSI Technology
The LSIU80ALVD fully supports Ultra2 SCSI. Ultra2 SCSI is an extension
of the SCSI Parallel Interface 2 and 3 (SPI-2 and SPI-3) family of
standards that expands the bandwidth of the SCSI bus, allowing faster
synchronous data transfers.
For the internal bus, special impedance SCSI ribbon cables are specified
for operation with Ultra and Ultra2 SCSI devices. You must consider the
total length of the bus cables and the number of devices on the SCSI
bus when setting up your system.
Use SCSI cables that have been rated for standard SCSI (Fast, Ultra,
and Ultra2) environments.
See Chapter 2, “Installing the LSIU80ALVD,” for a detailed explanation of
SCSI bus connections.
1.3.4 LVDlink Technology
To support greater device connectivity and a longer SCSI cable, the
LSIU80ALVD features LVDlink technology, the LSI Logic implementation
of Universal LVD SCSI. LVDlink transceivers provide the inherent
reliability of differential SCSI, and a long-term migration path to faster
SCSI transfer rates.
The LVDlink transceivers reduce the power needed to drive the SCSI
bus, so that the I/O drivers can be integrated directly into the chip.
LVDlink technology lowers the amplitude of noise reflections and allows
higher transmission frequencies.
The LVDlink transceivers operate in LVD and SE modes. They also allow
the chip to detect a High Voltage Differential (HVD) signal when the chip
is mistakenly connected to external HVD transceivers. The LSI53C895A
automatically detects which type of signal is connected, based on the
voltage detected, and automatically switches as needed to the SE or LVD
mode. All bus devices must be LVD or SE. If a HVD device is detected,
the board puts the SCSI bus in the high impedance state and shuts
down.