SCSI Functional Description
2-23
CRC – CRC is the error detecting code used in Ultra160 SCSI. Four
bytes are transferred with data to increase the reliability of data transfers.
CRC is used in the DT Data-In and DT Data-Out phases only. Because
CRC is implied with DT mode and only works with DT mode, the DT
setting can be used for CRC.
DT Clocking – Ultra160 SCSI implements DT clocking to provide
speeds up to 80 megatransfers/s. DT clocking means that the data is
sampled on both the asserting and deasserting edge of REQ/ACK.
DT clocking is only valid using a LVD SCSI bus.
In order to support DT clocking, there are two new phases for the SCSI
bus. The old Data-In and Data-Out phases are now called ST Data-In
and ST Data-Out. The new phases are DT Data-In and DT Data-Out.
The use of DT and ST phases implies that the SCRIPTS engine may use
a different jump point for DT or ST.
illustrates SCSI signal
configuration for these phases.
To indicate DT or ST mode, a bit is set in the current “selection” data
reserved byte. BMOVE instructions identify the current BMOVE as either
DT or ST through the phase bits.
Table 2.3
New Phases on SCSI Bus
Phase
MSG
C/D
I/O
Description
ST Data-Out
0
0
0
–
ST Data-In
0
0
1
–
DT Data-Out
1
0
0
Previously reserved
DT Data-In
1
0
1
Previously reserved
Содержание LSI53C1000
Страница 6: ...vi Preface...
Страница 16: ...xvi Contents...
Страница 28: ...1 12 Introduction...
Страница 234: ...4 124 Registers...
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Страница 350: ...6 76 Specifications Figure 6 42 LSI53C1000 329 Ball Grid Array Bottom view...
Страница 352: ...6 78 Specifications...
Страница 360: ...A 8 Register Summary...
Страница 376: ...IX 12 Index...