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1.12
Low-Voltage Differential
1.12.1
Ultra2-SCSI
The SPI-2, Fast-40 Standard defines the characteristics of cables, signals, and transceivers required
for 40 MB/s signal transmission. The services required to communicate with a higher layer
protocol is defined by the SPI-2.
In addition, the expansion to SPI-2 parallel interface is defined to enhance the available data
transfer rate. Only the interface specifications associated with the higher data speed are included
in this Standard.
1.12.2
Ultra-160
The technologies of the following are added since Ultra2-SCSI:
(1) DT data transfer mode (Up to maximum data transfer rate :160MB/s)
(2) Domain Validation (Write/Read Buffer Command with Echo Buffer Option)
(3) Parity CRC Available (P_CRCA) (DATA Phase CRC Protection)
These technologies are included in Ultra3-SCSI and are part of it. The name "Ultra-160" isn't in
SCSI Parallel Interface – 3 (SPI-3) but is generally well known in the hard disk market. The
technology "Ultra-160" enable synchronous data transfer rate of more than 80 megatransfers per
second and less than or equal to a transfer rate of 160 megatransfers per second. And Ultra-160 is
supported only in LVD mode.
The DT data transfer mode in detail is written in Subsection 1.6.5.2 compared ST data transfer
mode.
The act of verifying that the physical layer is able to transfer test data at the negotiated speed and
width between the INIT and TARG — (i.e., a quick check for physical domain validation). For
example, two wide SCSI devices connected with a narrow cable will discover that the cable does
not support wide transfers during this checking. These SCSI devices will then re-negotiate to
narrow transfers.
A signal sourced by a target during DT DATA phases to control whether a data group field is a pad
field, pCRC field, or data field. When asserted the data group field shall be pad or pCRC fields
that shall not be transferred to the ULP. When negated the data group field shall be a data field that
shall be transferred to the ULP.
1.12.3
Ultra-320
The new technologies of the following are added since Ultra-160 SCSI:
(1) Paced transfer mode (Up to maximum data transfer rate :320MB/s)
(2) Information unit transfer(All information transfers are performed in DT Data-In and DT Data-
Out phase, except for QAS message)
These technologies are included in Ultra4-SCSI and are part of it. The name "Ultra-320" isn't in
SCSI Parallel Interface - 4 (SPI-4) but is generally well known in the hard disk market. The
technology "Ultra-320" enable synchronous data transfer rate of more than 160 megatransfers per
second and less than or equal to a transfer rate of 320 megatransfers per second. And Ultra-320 is
supported only in LVD mode.
1-134
C141-C011
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