Interface Control
The
INTERFACE CONTROL command allows
the
Initiator
to
send
an
ESDI command
directly
to
the
disk drive ESDI interface.
If
this command returns a Check Condition
status,
the
subsequent Request Sense command will, in most cases,
return
a Sense Key of 01,
and
an
additional Sense Code
of
44H, whether or
not
the
command completed correctly. However,
the
Vendor Unique
DERROR
status
code will
be
valid.
Interface
Control
Command
Descriptor
Block
(COB)
Bit
Byte
7
I
6
I
::;
I
4
I
3
I
2
I
1
I
0
00
Opcode =
EFH
01 Logical Unit
Number
I
Reserved
I
Status
02-03
(MSB=02)
Command
(LSB=03)
04-08
(MSB=04)
Reserved
(LSB=08)
09
Control
Byte
Status.
If
this byte is set
to
one (1), two (2) bytes of ESDI
status
information will
be
received
from
the
disk drive
and
returned to
the
Initiator
in addition
to
the
interface
status
byte
described below.
Note
~
There is
no
interface timeout on this command.
It
is
the
Initiator's
responsibility
to
issue valid commands and
to
set
the
STAT
bit
only for
commands which will normally
return
status
information.
A single byte will be returned
to
the
Initiator
when
the
disk controller completes
its
operation.
The
byte
has
the
following
bit
definitions:
• Bit 0 - Disk drive selected
• Bit 1 -
Command
complete
• Bit 2 - Ready
•
Bit
3 - Attention
• Bits
4-
7 - Undefined
Command. This field is
the
ESDI command for
the
disk drive.
B·10
Vendor
Unique
Command
Descriptions
DRAFT
1/18/93 09:58
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