Fujitsu 80, Scsi Logical Interface Specifications

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C141-C010 5-1
CHAPTER 5 Sense Data Error Recovery Methods
5.1 Sense Data
5.2 INIT Error Recovery Methods (Recommended)
5.3 Disk Drive Error Recovery Processing
In this chapter, the configuration and contents of sense data reported to the INIT (initiator) when an error occurs,
etc., key information for interpreting error states, recommended procedures for error recovery processing that
should be executed by software in the INIT and error recovery processing executed internally by the IDD are
described. Furthermore, see Chapter 3, “SCSI Bus Error Recovery Processing” in the “SCSI Physical Interface
Specifications” concerning recovery processing for errors detected in operations on the SCSI bus.
5.1 Sense
Data
When the IDD reports a CHECK CONDITION status, or in cases when some fatal error is detected in
connection with the SCSI bus, and as a result, the command that is currently being executed, or the commands
in the stack are cleared, it generates sense data for the INIT that issued that command. The INIT can fetch the
sense data by issuing a REQUEST SENSE command.
5.1.1
Sense data format
The IDD’s sense data is in the so-called “Expanded Sense Data” format. The expanded sense data
format supported by the IDD is shown in Figure 5.1.
Notes:
1. In the SCSI specifications, each device is permitted to define whatever it chooses after byte 18
of the expanded sense data, and the length and format differ for each device. The length of
expanded sense data is displayed in the sense data, so by analyzing the sense data which it
receives, the INIT can know its effective length.
2. In the REQUEST SENSE command, even if a Transfer byte length that is shorter than the
length of the sense data supported by the device which is the object of the command, the
command will terminate normally, but in that case, some of the sense data only will be received
and the remaining information will be lost. Sufficient caution should be exercised with regard
to the devices connected to the INIT and all the sense data of those devices should be read.