Control Characters - Heathkit H9 Manual

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CONTROT CHARACTERS
The Terminal generates all 32 ASCII control charac-
ters from the keyboard. Normally these characters do
not write into RAM, nor are they displayed on the
screen. Exceptions are outlined in the description of
the plot mode. The Terminal recognizes only four of
the control characters. It will recognize these from the
keyboard or from the parallel or serial input ports.
The four characters are:
Line Feed (LF or CTRL ]) - This character du-
plicates the LINE FEED key.
Carriage Return (CR or CTRL M) - This charac-
ter duplicates the RETURN key.
Back Space (BS or CTRL H) -
This character
moves the cursor to the left one character posi-
tion without disturbing the character being dis-
played.
Bell (Bel or CTRL G) - This character causes the
Terminal to sound a short audible tone through
an internal speaker. Pictorial 1-3 shows the con-
trol and normal characters thattheTerminal can
generate.
HOLD SCREEN
If the screen has been filled, and a scroll function
should occur, but can't because the SCROLL key is
not pushed in, the Terminal goes into the hold screen
mode. The cursor returns to the start of page location
and blinks. All external inputs are disabled when this
occurs. Data can only be transmitted out of the Termi-
nal by the keyboard. The Terminal stays in the hold
screen mode until the SCROLL key is pushed in or
until the ERASE PAGE key is pressed.
You can use this feature in conjunction with the paper
tape reader/punch for reviewing program tapes. The
reader/punch can read the tape at its maximum speed
to fill up the screen quickly, then after the last line has
been written, the hold screen mode disables the
handshake signal coming from the Terminal. This
stops the tape from running. You can then review the
contents of the screen. When you are finished, just
press the ERASE PAGE key and receive another
screen full of program information automatically.