HOST SOFTWARE INTERFACE
6 – 1
SECTION 6
Host Software Interface
The host communicates with the drive through a set of controller registers accessed via the host’s I/O ports.
These registers divide into two groups: the Task File, used for passing commands and command parameters and
the Control/Diagnostic registers.
Task File Registers
The Task File consists of eight registers used to control fixed disk operations. The host accesses each register
by the I/O port address shown in this Task File register map:
T
R
O
P
O
/
I
D
A
E
R
E
T
I
R
W
h
0
F
1
r
e
t
s
i
g
e
R
a
t
a
D
r
e
t
s
i
g
e
R
a
t
a
D
h
1
F
1
r
e
t
s
i
g
e
R
r
o
rr
E
r
e
t
s
i
g
e
R
s
e
r
u
t
a
e
F
h
2
F
1
t
n
u
o
C
r
o
t
c
e
S
t
n
u
o
C
r
o
t
c
e
S
h
3
F
1
r
e
b
m
u
N
r
o
t
c
e
S
r
e
b
m
u
N
r
o
t
c
e
S
h
4
F
1
w
o
L
r
e
d
n
il
y
C
w
o
L
r
e
d
n
il
y
C
h
5
F
1
h
g
i
H
r
e
d
n
il
y
C
h
g
i
H
r
e
d
n
il
y
C
h
6
F
1
)
H
D
S
(
d
a
e
H
/
e
v
ir
D
)
H
D
S
(
d
a
e
H
/
e
v
ir
D
h
7
F
1
r
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t
s
i
g
e
R
s
u
t
a
t
S
r
e
t
s
i
g
e
R
d
n
a
m
m
o
C
Data Register
Provides access to the drive’s sector buffer for read and write operations. With the exception of ECC byte
transfers (which, during Read long and Write long commands, are 8 bits wide), data transfers through the
Data register are all 16 bits wide.
Error Register
A read-only register containing specific information regarding the previous command. Data interpretation
differs depending on whether the controller is in operational or diagnostic mode. A power up, reset,
software reset, or receipt of a diagnostic command sets the controller into diagnostic mode. This mode
invalidates contents of the Status register. The contents of the Error register reflect a completion code.
Issuing any command (apart from a Diagnostic command) places the controller into
operational mode
.
In operational mode, the Error register is valid only when the Error bit in the Status register is set. The bit
definitions for operational mode follow:
7
6
5
4
3
2
1
0
0
C
C
E
0
F
N
D
I
0
T
R
B
A
0
K
T
F
N
M
A
e
c
a
fr
e
t
n
I
C
R
C
a
t
a
D
r
o
rr
E
C
C
E
t
o
N
d
e
s
U
D
I
d
n
u
o
F
t
o
N
t
o
N
d
e
s
U
d
e
tr
o
b
A
d
n
a
m
m
o
C
0
k
c
a
r
T
r
o
rr
E
s
s
e
r
d
d
A
t
o
N
k
r
a
M
d
n
u
o
F
Interface CRC
– An interface CRC error occurred during an Ultra DMA transfer.
Data ECC Error
– An non-correctable ECC error occurred during a Read Sector command.
Firmware Problem
– Indicates a firmware problem was detected, (e.g., invalid interrupt, divide overflow).
ID Not Found
– Either a matching ID field not found, or a CRC error occurred.
Aborted Command
– Invalid commands, write fault, no seek complete, or drive not ready.
Track 0 Error
– Track 0 was not found during execution of a Restore command.
Address Mark Not Found
– The Address Mark could not be found after an ID match.
Features Register
Enables or disables features through the Set Features command.