Request Sense Command - Seagate STT20000A Product Manual

ATAPI Interface

Request Sense command

Bit 7
Byte
0
1
2
3
4
5
STT20000A Product Manual
6 5
An Allocation Length value of 20 will return all Request Sense data.
The Request Sense command is always accepted, regardless of the state of the
DSC bit, but the status is valid only when DSC or CHK (error) is set (1). If DSC and
CHK are both reset (0), a non-error "null" status is returned. Normally, if CHK is set,
DSC is set. The only time CHK is set and DSC is reset, is during writes at logical
end of media; DSC remains a buffer indicator, and CHK is set to indicate EOM,
which is a warning, not an error.
If a command completes with a check (error) condition, the next command issued, if
not Request Sense or Inquiry, will be aborted, and a deferred error will be reported.
If the command is Request Sense, a non-deferred error is reported. The Inquiry
command does not affect status reporting.
The following table describes the REQUEST SENSE layout.
Byte Description
0 Valid, Error Code
1 Reserved (Segment Number)
2 Filemark, EOM, ILI, Sense Key
4 3
Operation code (03h)
Reserved
Reserved
Reserved
Allocation Length
Reserved
Value
70h,71h
00
NN
Chapter 5
2 1
Meaning
80h = Information Field Valid
+ 70h = Current Errors
or 71h = Deferred Errors
—
80h = Filemark
+ 40h = EOM
+ 20h = ILI
+ Sense Key
0
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