Alpha Mode - Tektronix 4010 Maintenance Manual

RESPOND TO DA TA FROM THE COMPUTER; THE
KEYBOARD IS SIMPL Y BEING USED AS A SOURCE OF
DATA FOR THE RECEIVING CIRCUITS WHILE IN
LOCAL OPERA TlON.
Initial ization
Press the PAGE key to erase the display screen. The
screen must be initialized by erasing it each time the
Terminal is turned on. PAGE also selects Alpha Mode and
places the beam at the upper-left corner of the display
(Alpha Mode "home" position).
Alpha Mode
Character Transmission and Character Effect. Press each
key in the keyboard cluster and note the effect. Most of
them will cause character writing, permitting a check of the
code being transm itted by the keyboard and a check of the
dot pattern being presented by the character generator in
the receiving circuits. Keys which are an exception to this
are as follows:
PAGE-Causes no transmiSSion. A direct connection
to the receiving circuits causes Alpha Mode to be
selected. It also causes erasing and places the Alpha
cursor to the top-left corner of the display (Alpha Mode
"home" position).
AL T MODE-Causes neither writing nor spacing,
although the keyboard transmits the ASCII character for
closing brace.
LINE FEED-Transmits the control character LF. At
the receiving circuits, LF causes the Alpha cursor to
move down to the next line. The cursor may also move
to the left margin if the "LF Causes Carriage Return"
strap option on TC-1 is at IN position.
RETURN-Transmits the control character CR. At
the receiving circuits, it causes the Alpha cursor to move
to the left margin. There are two "left" margin
positions. One is vertically aligned with the "home"
position and is referred to as "Margin
~".
The second is
near the horizontal center of the screen, and is referred
to as "Margin 1 ". Margin 1 is automatically selected each
time the Terminal line-feeds past the 35th (last) line
while Margin ~ exists. Margin ~ is selected when the
Terminal line-feeds past the 35th line while Margin 1
exists, and is also selected when ESC FF is received or
when PAGE or RESET is entered at the keyboard.
®I
CTR L-Has no effect as a single key entry. It causes
the keyboard to transm it control characters when used
Installation and Operation-4010 Maintenance
with other keyboard keys. For example, entering a G
while the CTRL key is held down rings the bell, since it
transmits the control character BEL; and the receiving
circuits accept that as the command to ring the bell. As a
second example, holding down CTRL and SHIFT and
pressing K transm its the control character ESC. No
reaction is evident at the Terminal, since the receiving
circuits recognize it as an arming command, and wait for
a second command before they act. Now enter CTRL L
and note that the control character FF is transmitted,
accepted by the receiving circuits, causes the display to
erase and the Alpha cursor to go home. F F alone cannot
do it. It must be preceded immediately by ESC. A
complete listing of control character effects appears in
Table 2-1.
RUBOUT -This key sends the ASCII code for DEL.
The receiving circuits accept it, but it causes no spacing,
writing.
RESET -Causes no transmission. A direct connection
to the receiving circuits causes Alpha Mode to be
selected and causes the Alpha cursor to move to the
home position.
BREAK-Sends a break signal to the interface unit,
which may then transmit a break signal to the computer.
Has no effect upon the receiving circuits.
SH I FT -Its only effect as a single key entry is to
restore View condition without otherwise affecting
transmission or the receiving circuits. When used with
other keys, it causes the shifted (upper) character to be
transmitted as indicated on each key. Exceptions to this
occur on the E, R, T, I, S, D, and L keys, where the
upper inscription indicates the TTY character which is
sent when those keys are pressed while CTRL is held
down. Except for L, those keys send the same character
while the SHIFT key is held down as they do when
pressed alone. The L key sends a reverse slant line if
pressed while the SHIFT key is held down.
Automatic Line Feed and Carriage Return. By now, it
probably has been noticed that the Terminal receiving
circuits automatically perform a carriage return and line
feed each time the last (74th) character in a line is written.
If it hasn't been noticed, enter a full line of characters and
observe the effect. Note that the Alpha Cursor returns to
the effective margin position-Margin
a
or Margin 1.
Margins. Enter a PAGE command and note the cursor
position at the left edge
(Margin~)
of the display. Enter
LINE FEED commands until the cursor disappears past the
bottom of the display screen, and note that it re-appears at
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