Section 5
SCSI Programming Guidelines
PAGE CODE (Byte
2,
Bits 5-0) -
For
all the above options, the Page Length byte value
returned indicates the number
of
bytes the ProDrive supports within each page. This value must be
specified in the
Page Length field (Byte 1
of
each Page Descriptor) when issuing the
MODE
SELECT
command.
The
page code specifies the particular page information to be returned to the initiator in the
MODE
SENSE
data. The ProDrive supports the following pages:
Page
-
OIH
02H
03H
04H
37H
38H
39H
3FH
Description
Read/Write Error Recovery Parameters
Disconnect/Reconnect Control Parameters
Direct-Access Device Format Parameters
Rigid Disk Drive Geometry Parameters (valid for
MODE
SENSE
command
only)
Quantum
Unique Control Parameters
Read-only; included for compatibility with
Q200
Series drives
Quantum
Unique Drive Conttol Parameters
Return all pages to
the
initiator (valid for
MODE
SENSE
command only)
The
MODE
SENSE data provides information to the initiator
on
the configuration
of
the
ProDrive's Format Parameters and Drive Geometry Parameters,
if
Pages
03H
and
04H,
respectively,
are specified.
If
Page 3FH is specified, information from all pages implemented by the ProDrive
will be returned to the initiator in the
MODE
SENSE data. This page code is only valid in the
MODE
SENSE
command.
Spedfying
page code 04H in a MODE
SELECT
command will result in a
CHECK
CONDmON
status with Illegal Request sense key.
NOTE:
If
the allocation length is set
tol2
bytes
or
less. the page code field is ignored and illegal
page numbers are accepted.
If
the allocation length is greater than 12 bytes,
an
illegal page
code will be rejected. This allows the initiator to receive the 4-byte header
and
8-byte block
descriptor without receiving specific page information.
ALLOCATION LENGTH (Byte
4)
- Specifies the number
of
bytes the initiator has allocated
for returned
MODE
SENSE data. An allocation length
of
zero indicates that
no
MODE
SENSE data
will be transferred. Any other value indicates the maximum number
of
bytes that should be
transferred.
The
ProDrive will terminate the
DATA
IN phase when allocation length bytes have
been transferred
or
when all available
MODE
SENSE data have been transferred to the initiator,
whichever is less.
MODE SENSE DATA -
The
MODE
SENSE
data (Table 5-28) contain a four-byte header,
followed
by
an
eight-byte block descriptor, then zero
or
more "pages".
The
meanings and organization
of
these data are the same as for the corresponding
MODE
SELECT data (Section 5.11.10.2), as
modified
by
the option specified in the page conttol field
of
COB
byte 2.
SCSI
Programming
Guidelines
5-55
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