Heathkit H9 - Control and Special Keys

Page 7
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BREAK
When this
key is
pushed
in,
it
generates
a
continuous
space
at the
serial
output,
It is
generally
used
to tell
the
computer
that
you
wish
to interrupt
execution.
Do
not
confuse
this
space with
an ASCII
space. It
is de-
fined
as
zero
current in
a 20 mA
current
loop,
an
EIA
positive
voltage,
or a TTL logic
0. The BREAK
key
can
be
pressed
any time
you
want
to terminate
the trans-
mit
page
function.
FULL
DUPLEX
When this key is
released
(out),
the Terminal
operates
in
the half
duplex mode.
That is,
data from
the
keyboard
or
parallel
input
is written
directly into
RAM
and, at
the same time,
ASCII
characters are
sent
out the
serial and
parallel
outputs.
When the FULL
DUPLEX
key is
pushed
in,
the Terminal
operates in
the full
duplex
mode. Data
from
the
parallel
input
or
from
the keyboard
is
sent to the
computer and
echoed
back to
the Terminal
before it
is written into
RAM
and
displayed
on the
screen.
XMIT
PAGE
(Transmit
Page)
When
you
momentarily press
this key,
data
is
trans-
mitted from
the RAM
(screen),
starting from
the cur-
rent
cursor location
and
proceeding
to the
end of the
page.
When
it has
completed
the
page,
the
cursor
returns
home
and the transmit page
mode
stops. The
data is
transmitted
simultaneously
outboth
the
paral-
lel
and serial ports
at a rate
determined
by
the
slower
of the
two
ports.
Press
the BREAK
key to
interrupt
the
transmit page
function.
CTRL
(Control)
When
this key is
used
in
conjunction
with
some
of
the
other keys,
it
changes
those
keys
to special
function
keys.
For instance,
CTRL M is
equivalent
to
a return
(carriage
return).
The
control key
combinations
are
shown
in Pictorial
1-3.
SHIFT
When
this
key is
used in
conjunction
with another
key,
the
character
printed
on the upper
portion
ofthat
key will
be
displayed.
Since
the Terminal
does
not
generate
lower-case
alphabetic
characters,
it is
not
necessary
to
push
the
shift key
to
generate
upper-case
alphabetic
characters
-
they
are shifted
automati-
cally
in the
keyboard
encoder.
CTRL/SHIFT
These
two keys
are
used in
conjunction
with
other
keys
to
provide
additional
special function
keys. For
instance,
CTRL/SHIFT
P
(which
means, press
the
CTRL,
the
SHIFT,
and
the P
keys at
the
same time)
puts
an ASCII
null
fall
zeros)
on the bus.