Section 5 SCSI Programming Guidelines
5.11.13
MODE SENSE COMMAND: OPCODE = 1A(hex)
The MODE SENSE command (Table 5-27) provides a means for the target to report its peripheral device
parameters to the initiator. This command complements the
MODE SELECT command.
5.11.13.1 MOPE SENSE Command Structure
TABLE
5-27 MODE
SENSE
Command
Bit 7
6 5 4
3
2 1
o
Byte
0
OPCODE=
lAH
I
LUN=O
I
RESERVED=O
2 PCF
I
PAGE CODE
3
RESERVED = 0
4
ALLOCA
nON
LENGTH
5
VU:::(}
I
RESERVED
=0
I
F
I
L
PCF
-
PAGE
CONTROL
FIELD
(Byte 2, Bits 7,6) - Defines the type
of
page parameter
values to
be
returned. There are four options:
Report Current Values
(PCF = 00)
The page defined by the page code is returned to the initiator with fields and bits set to current values.
The current values are either:
• as set in the last succe&sfully completed MODE SELECT command
• identical to the saved values
if
no MODE SELECT commands were issued since the last power-up
or
reset.
Fields and bits not supported by the
ProDrive are set to zero.
Report
Chanaeable Values (PCF = 01)
The page defined by the page code is returned to the initiator with all fields and bits changeable by the
initiator set to ones. Fields and bits not allowed to
be
changed by the initiator are set to zero.
Report Default Values (PCF
=
10>
The page defined by the page code is returned
to
the initiator with fields and bits set to the
ProDrive's default values (i.e. as shipped from the factory). Fields and bits not supported by the
ProDrive are set to zero ..
If
there is confusion over whether a returned value
of
zero indicates a
default parameter
or
a nonsupported parameter, the initiator can examine the changeable values.
Report
Saved. Values (PCF = 11)
The page defined by the page code is returned to the initiator with fields and bits set to saved values.
The saved values are either:
• as set in the last successfully completed MODE SELECT command with the SP (Save Parameters)
bit
O.
byte 1
of
the CDB set to one.
• identical to the Default values if no MODE SELECT commands with the SP bit set were ever
issued (and completed successfully).
Fields and bits not supported by the
ProD rive are set to zero.
5·54
SCSI
Programming
Guidelines
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