as a line receiver
and
a line driver between the
I/O
interface and the Read/Write PCBA. The
Unit
Select Logic, the Busy Output logic, and the Ready driver are also included
as
minor
elements in the Disk Drive Function
Control Logic. Likewise, the ReadlWrite Control
logic,
the Write Protect logic including the Write Protect Lamp Drivers are part
of
the Disk
Drive Function
Control Logic. Additional minor functions are performed by the
Read
Signal Drivers, the Malfunction Signal Driver, the Double Track Status Driver, the Illegal
Address Status Driver,
and
the Dual Platter Status Driver. These functions are described in
terms
of
function and purpose,
as
follows.
Two
1/0
interface control lines
are
provided for selecting a specific storage surface. These
lines
are
the Head Select (IHXSR) and Platter Select (IPSXR). Two other
I/O
interface
control lines, Track
Offset Plus (ITOPR)
and
Track Offset Minus (ITOMR) are provided
for
selecting specific track offsets for diagnostic purposes. The four lines, Head Select,
Platter Select, Track Offset Plus, and Track Offset Minus
are
processed by the holding
register and distributed to the ReadlWrlte
PCBA. The Track Offset Plus and Track Offset
Minus lines are also distributed to the Servo PCBA.
The
Holding Register performs a holding function to store the status of these lines under
certain conditions. These conditions are determined by the
Selected And Ready and the
Not
Ready
conditions. The Write Double Frequency Data Re-transmitter acts
as
a line
receiver for the 110 interface
lineWrite
Data Signal (IWDSR) and re-transmits the signal
to
the
Read
/Write PCBA as the Write Double Frequency signal. This acts as a butter
and
maintains timing of the Write Double Frequency signal.
Another minor function provided by the Disk Drive Function Control Logic is contained in
the Unit
Select logic. This logic combines the setting of the Unit Number Selector switch
on
the operator panel with the specific Unit Select Number signal from the
I/O
interface.
Decoding is performed and the
Select signal is generated only when the Unit Select line
from the
1/0
interface corresponds to the number designated for the specific disk drive by
the Unit Number
Selector switch
on
the operator panel.
Also
contained within the Disk Drive Function Control Logic is the Busy Output logic. This
logic combines the busy signal from the Position Control Logic with the Ready signal
and
encodes on a specific Busy Seeking line according to the setting of the Unit Number
Selector switch on the operator panel.
A number of line driver functions
are
performed by various signal drivers. These drive
internal
logiC signals onto the
I/O
interface lines
as
outputs
of
the disk drive. These
are:
(1)
The
Ready Driver
for
driving the selected and ready signal onto the Ready line at
the interface.
(2)
The
Read
Signal Drivers for transmitting the outputs
of
the Read/Write PCBA
on the
Read
Data and
Read
Clock
I/O
interface lines.
(3)
The
Malfunction Signal driver
for
transmitting the malfunction pulse
on
the 110
interface line.
(4)
A Double Track Status interface line for indicating at the
I/O
interface when a disk
drive is a
200-tpi model.
(5)
The Illegal Address Status driver for transmitting the illegal address signal to the
Illegal Cylinder Address 110 interface line.
(6)
Dual
Platter Status signal driver for indicating
on
the Dual Platter Drive
I/O
interface line that the disk drive contains two platters.
4-21
630D
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