(
f
(
Tape
Adapter
I/O
Lines
Refer to the
Tape
Control Card logic diagram in Section
5.
Controls
The control lines control all tape operations. The control
lines and their uses are:
'-POR Switch'-Resets the registers
in
the tape
adapter when the RESTART switch is pressed.
'+Oscillator' -Provides a 15.091 MHz signal
to
generate interrupts when writing data on tape. This
signal is sent
to
the tape control card as a 3.7728
MHz tape clock signal.
'+
Tape
C/ock'-Clocks the read clock counter that
distinguishes between clock pulses and data pulses
(flux reversals) coming from the read head. 'Tape
clock'
also
provides timing
pulses
for
the
bit
interval
timer counter. The
bit
interval timer counter
measures the time between clock pulses coming from
the read head. The 'tape clock' signal is a free
running square wave signal at 3.7728 MHz; symmetry
must be better than 33
% .
'+Device Address XO-X3, YO-Y3'-lndicates the device
to
be used
by
the controller. The tape unit uses
device address F
for
clearing all latches and registers,
and device address E
for
all other operations. 'Device
address X3 and Y3' lines must be up
for
a device
address
F.
'Device address lines X3 and Y2' must be
up
for
device address
E.
'-Control Strobe' -Signals the tape adapter that the
information on bus out
0-
7 is
not
a command data.
'-Put
Strobe' -Signals the tape adapter that the
information on bus out
0-7
is data, not a command.
•
+Op
Code
E'-Signals the tape adapter
to
gate data
or status
onto
bus in.
It
is also used
to
simulate data
from
the tape control card during diagnostic testing
and
for
subdevice addressing.
'-Get
Strobe'
-Signals
the tape adapter
that
information
from
its registers on bus
in
was sampled
by the controller. The tape adapter then clears this
information
from
the registers.
'+Start
Execute'
-Signals
the tape adapter that
it
can
sample the device address lines and bus
out
lines
for
information. During start execute time, parity is
checked on bus
out
and the device address lines are
tested
for
a device address check.
, -Machine Check' -Signals the controller that either a
bus out check or a device address check occurred.
A bus out parity check occurs when bus
out
parity is
not odd. The bus out condition can be cleared only
by
pressing RESTART or by turning
power
off.
A device address check occurs when the eight 'device
address' lines
do
not have even parity. A correct device
address for the tape unit is 'device address X3 and Y3'
up (device address
F)
or 'device address X3 and Y2' up
(device address
E)
(refer
to
the Base
I/O
Card logic
diagrams). A device address check can be cleared only
by pressing RESTART or by turning power off.
Commands
Tape unit commands are generated by the microprogram
microinstructions located in executable
ROS.
The
microprogram sends commands from the controller
to
the tape adapter. The following table indicates the bus
out
bits and the associated commands when used with
a device address
E.
Bus
Out
Bit Bit
= 0
(Off)
Bit
= 1 (On)
0
Run
Stop
Forward
Reverse
?
Channel 1 select
Channel 0 select
3
Write
Read
4
Channel 0
erase
Not
channel 0 erase
5
Channel 1
erase
Not
channel 1
erasp.
6
Diagnostic
Not
diagnostic mode
7
Interrupt enabled
Interrupt disabled
Tape 4-41
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