VIPER SCSI 60, 125 & 150 THEORY
OF
OPERATION AND MAINTENANCE
Chapter 4
Interface .................................................................................................................................... 4-1
4.1
Overview.....................................
........
................................................................................ 4-1
4.1.1 ANSI SCSI Bus Standards....................................................................................... 4-1
4.1.2 Signal Notation Conventions ................................................................................. 4-1
4.2
SCSI
Bus Connector Signals ............................................................................................. 4-2
4.3 Signal Descriptions
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4-3
4.4
Command
Set Description............................................................................................... 4-4
4.5
SCSI
Bus Protocol.......................
...
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...
..................................... 4-5
4.6 Waiting
and
Control Phases............................................................................................. 4-6
4.6.1 Nonarbitrating Systems........................................................................................... 4-6
4.6.2 Arbitrating Systems ................................................................................................. 4-6
4.7 Selection
and
Reselection Phases .................................................................................... 4-9
4.8 Information Transfer Phases ........................................................................................... 4-10
4.8.1 Asynchronous Data Transfer ................................................................................ 4-10
4.8.1.1 Transfer from Target
to
Initiator ................................................................. 4-11
4.8.1.2 Transfer from Initiator to Target ................................................................. 4-12
4.9
Command
Phase ............................................................................................................... 4-13
4.10 Data Phase........................................................................................................................ 4-13
4.10.1 Data-In Phase ......................................................................................................... 4-13
4.10.2 Data-Out Phase...................................................................................................... 4-13
4.11 Status Phase ..................................................................................................................... 4-13
4.12 Message Phase................................................................................................................. 4-13
4.12.1 Message-In Phase .................................................................................................. 4-13
4.12.2 Message-Out Phase............................................................................................... 4-14
4.13 Con1mand Descriptor Block.......................................................................................... 4-14
4.14
SCSI
Message Descriptions
and
Definitions............................................................... 4-16
4.15
SCSI
Status Code Descriptions
and
Definitions......................................................... 4-19
4.16 Attention Condition ....................................................................................................... 4-21
4.17 Reset Condition............................................................................................................... 4-21
4.18 Unit Attention Condition .............................................................................................. 4-21
4.19 Buffered Mode................................................................................................................. 4-22
4.20 Imn1ediate Function ....................................................................................................... 4-22
4.21 Residual Length Function ............................................................................................. 4-22
4.22 Disconnect/Reconnect Function .................................................................................. 4-24
4.23 SCSI Memory Address Pointers ................................................................................... 4-25
4.23.1 Current Data Pointers........................................................................................... 4-25
4.23.2 Saved Data Pointers .............................................................................................. 4-25
4.24 Early Warning Function ................................................................................................ 4-25
4.25 Error Reporting ............................................................................................................... 4-26
4.25.1 Soft Errors............................................................................................................... 4-26
4.25.2
Hard
Errors ............................................................................................................ 4-26
4.26
SCSI
Bus Phase Timing .................................................................................................. 4-26
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