Read Headers
The
READ HEADERS command will read all
the
headers
on
the
track
specified by
the
Address field
and
return
the requested number of bytes.
The
header information will always
be
returned
starting
from physical sector 0 of
the
addressed track regardless of
the
addressed
block or sector.
READ HEADERS Command Descriptor Block (CDB)
Bit
Byte
7
I
6
I
5
i
4
i
3
i
2
i
1
i
0
00
Opcode
=
EEH
01
Logical Unit
Number
I
Reserved
I
PHYS
02-05
(MSB=02)
Address
(LSB=05)
06
Reserved
07-08
(MSB=07)
Allocation
Length
(LSB=08)
09
Control
Byte
PHYS (Physical Address).
If
the
PHYS
bit
is set
to
one (1),
the
address field is interpreted as
a physical address in
the
following format:
• Byte
2:
Cylinder Address (MSB)
•
Byte
3:
Cylinder Address (LSB)
•
Byte
4:
Head Address
• Byte
5:
Sector Address (Ignored)
If
PHYS is set
to
zero (0), the address
is
assumed to be a logical address.
Address. This field specifies which track
to
read.
Allocation Length. A value of zero
(0) in this field will cause a seek
to
the
addressed
track
with
the
header information read from
the
disk
but
no
data
transfer
to
the
Initia.tor.
B·20
Vendor Unique Command Descriptions
DRAFT
1/i8/93 09:58
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