Table of Contents
Advertisement
Order
Restore Carriage
Release
Select Test Mode
Invalid order
Binary Representation
Bit Positions
0 1 2 3 4 5 6 7
0 0
1 0 0 1
00
0001
0 0 0 1 0 0 1 1
0 0 0 0 0 0 0 0
Hexadecimal
Code
X'33'
X'23'
X'13'
where M signifies Modifier bit (explained under "Seek"
order).
SEEK (X'03')
The Seek order alerts the controller to request a 4-byte
address from the IOP, as indicated below. The controller
then directs any subsequent data transmission operation to
begin at this address.
Byte 0
Byte 1
Byte 2
Byte 3
0
Cylinder
I
0
I
Head
0
1 2 31"4 5
6 7 0 I
2
3 4
5
6
7 0 1 2 3 ..
5 6 7 0 1
2 3 • 5 6 7
where S signifies sector number.
A byte count of less than four causes the controller to sig-
nal incorrect length without completing the Seek operation.
If the byte count is greater than four, the Seek operation is
performed using the first four bytes transferred, but incor-
rect length wi 11 sti II be signaled. An "unusual end" termi-
nation will occur in either case.
An order Modifier bit (bit 0), when set, causes a device
interrupt to be initiated when the positioning system indi-
cates that positioning is complete or a Seek timeout error
(i.e., exceeding maximum time al lowed for arm movement)
has occurred. The interrupt call is always made at the be-
ginning of the sector prior to the one specified by the Seek
operation. However, if the controller is "busy" with
another device when the device signal is received, the
interrupt call to the IOP will be postponed until the con-
troller is "not busy". If the interrupt call is not serviced
before the beginning of the next sector, it will be post-
poned. Seek orders may be issued successively to several
devices and each device will interrupt as it completes its
operation.
A device interrupt may be cleared by an AIO or HIO in-
struction, or by an I/O Reset (from the computer control
panel). The AIO or HIO clears only a single device inter-
rupt, whereas the I/0 Reset simultaneously clears all
pending device interrupts.
If a Seek operation indicates a nonexistent cyl
inder(~203),
head
(~20),
or
sector(~6),
the controller wil I proceed
to an "unusual end" termination without signaling the de-
vice to seek. The Sector Unavailable
statu~
bit for TDV
will be set (see Table 6). An "unusual end" termination
will also occur if the arm is currently in motion when the
Seek order is received for the same device. (See Restore
Carriage order,)
6
Device Orders
SENSE (X'04')
The Sense order causes the control I er to transmit up to 10
bytes of information to the IOP, as follows:
Byte 0
Byte 1
Byte 2
Byte 3
0
I
Cylinder
I
0
I
Head
0
I
2
31 ..
5
6
7
0
I
2
3 4
s
6
7 0
1 2 3
.. s
6
7
0
1
2 3 4 5 6 7
Byte 4
t
Byte 5
Byte 6
Byte 7
H
0
I
CS
I
Diag~ostic
Status .By:tes
0 1 2 3 1 4 5 6 7 0 1
2 3 4
5 6
7 0 1 2 3 4
5 6 7 0 1
2 3 "
s
6
7
Byte 8
Byte 9
Diagnostic Status Bytes
1 2
3 4
0 1 2 3 4 5 6 7
where
s
signifies sector number.
M
signifies Modifier bit.
cs
signifies current sector number.
Note: Bytes 5-9 are used for diagnostic purposes. See
Table 3 for the function of the diagnostic status bits
in bytes 8 and 9.
Table 3. Sense Status Bytes 8 and 9
Byte
Bit
No.
No.
Function
8
0
Data parity error
1
Check-Write error
2
Sector verification error
3
Head verification error
4
Cylinder verification error
5
Sector address not zero at start of
header write operation
6
Difference select sent to device
7
Sector select sent to device
9
0
Control select sent to device
1
Head select sent to device
2
Cylinder select sent to device
3
Seek forward set
4
Read gate sent to device
5
Write and erase gate sent to device
6
Read cylinder select sent to device
7
Not used
Note: Bytes 8 and 9 are used by diagnostic programs.
tThree bits of byte 4 indicate current sector number, but if
the most significant bit (M) is a 1, the arm was in motion at
time of sense and current sector number is meaningless. If
the head number is nonexistent, (M) will also be a 1.
Advertisement
Table of Contents
