Pase'8
@
ments
the
+
12 counter,
This addresses
the next
line
of
information
if the
Auto
Carry
key
is
pressed
in.
If
the
Auto Carry
key
is released, and
end
of
line indication
wiII
keep the counters
from
going
to zero
(the
carry
pulse
will not
get
to the
+
12
counter)
.
The
cursor will
then stay at the
right
end of
the line.
A logic 1 from
pin
2
of
IC730
(5706
pin
9) causes the
carry and
borrow
pulses
from
the
+20
counter to
cascade into
the
+4
counter. A logic
i. from
pin
2
of
1C724
(5707
pin
10)
causes
the carry and
borrow
pulses
from
the
+4
counter to
cascade into the
+12
counter. These
two logic
signals are
generated
in the
ROMs
(IC724
&
IC730)
as a function
of Vp'
,
Short
Form,
Auto
Carry, Scroll,
+20
EOL
(End
Of
Line),
and
+4
EOL.
Vp' comes
from the master TPU
timing
(IC705B
pin
a) and it is logic 1 during re-
trace.
Short Form
comes
from
the
Short Form key
on the keyboard
(S70a
pin
10).
When the
short form input
is logic
1, the Terminal
is
in the long
form mode.
When
the short form
input is
logic 0, the
Terminal is in
the short
form
mode.
Auto
Carry
comes
from
the Auto
Carry key
on the keyboard
(5703
pin
10). The Termi-
nal is in the
auto carry mode
when
the auto
carry input
is logic
0.
Scroll comes from
the
scroll
command
(lC747A
pin
3). The
scroll
command is
logic
0 during
a scroll
operation.
+20
EOL
comes from
the RAM
and
counter
circuit board
(5705
pin
a). The
+20
EOL
input
is logic
1 when
the
count in the
+20
counter is
19.
+4
EOL
comes from the
RAM and
counter
circuit board
(5707
pin
7).
The
+4
EOL
input is
logic
0 when the
count in
the
+4
counter is
3.
The
EOL
and auto carry signals
defeat the C.U.
+zo
signal
whenever the auto carry
function is not
selected.
Short Form
In
short
form,
the cursor moves
from
the left to right
through a block of only 20 characters before being
returned
to the start
position
of
the next line. When it
fills
up a
block
of
zqO
characters, it
moves
to the
top/start
position
of the next block of characters.
The
+20
carry
pulses
increment the
+12
counter if
the Auto
Carry
key is
pushed
in. This accesses the
entire first block of characters
fwhen
the
+4
counter
outputs are zero). When the
+12
counter reaches 11
(L011),
and the
+20
counter reaches 19
(11001),
the
next
count
up
pulse
causes
the
+12
carry
pulse
to
increment the
+4
counter to
1
(01).
This
process
con-
tinues until
all four blocks have been accessed.
A logic 1. from
pin
2 of
IC730
(S706
pin
11) causes the
carry
pulses
from the
+20
counter to cascade
into the
+
1.2 counter.
A logic 1
from
pin
1
of
1C724
(S707
pin
8) causes the carry
pulses
from the
+12
counter
to
increment
the
+4
counter.
These logic signals are also
generated
as
a function
of
Vp'
,
Short
Form, Auto
Carry, Scroll,
+4
EOL, und
+20
EOL. Refer to the
"ROM
Programs" section
(in
the
"Semiconductor
Identification"
section of the
Manual) for the truth
tables
for ROMs 1C724
(444-1.2)
and IC730
(444-17).
Remember, the cursor
always indicates the RAM loca-
tion where data will be written.
Also, in long form,
data will enter
the RAM in 80
character
lines,
while in
short form, data will enter the RAM
in 240 character
columns.
Refer
to Pictorials
4-8,4-9,
and
+-t0 for a
summary
of
RAM locations
and cursor
movements.
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