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HP27130A
Edit Mode
Edit mode may be enabled by setting the Edit Mode option in Write Card Configuration (WCC),
Subfunction (SF) 1. Edit mode is disabled by clearing the Edit Mode option, or toggled by set-
ting the "toggle edit" bit in the Read Device data request (RQ
1),
subfunction bit 5. If toggled, the
change in state is for the duration of the request only, and will revert back to the static definition
(per WCC, SF I) when the request completes.
When working at a terminal connected to the MUX card, several types of editing capabilities
are available. The first is backspace to delete the previously typed character (several backspace
modes are available), and another is to delete the current line. An additional "quoting mode" (ex-
plained in the "Additional Options" paragraph) allows the insertion of editing characters in the text
buffer without causing any other action.
Note that editing can be performed on the current frontplane buffer
only.
Once a buffer has been
terminated for any reason, it cannot be modified by the card.
Backspace. The firmware uses the character BS (hex 08) to indicate a backspace function. This
character is generated by pressing the BACK SPACE key or by typing CNTL-H. In addition, you can
programmatically change the backspace character to any desired character by using the WCC, SF 6.
Three options are available to indicate that a backspace has occurred when the card is in
echoplex mode. The first option is "backspace echo". This option echoes a backslash character (5C
hex), followed by the character that was deleted from the input buffer.
The second option is "backspace overwrite". This option is· very useful
for
CRT-type terminals.
The firmware will echo a backspace - space - backspace sequence for each BACK SPACE key
hit, erasing the character from the screen.
The third option is "backspace only". This option echoes only the backspace character to move the
cursor under the deleted character.
The Backspace option is programmable by using
wce,
SF 8. Only one backspace option may be en-
abled at any time.
If you have used backspace to delete the current line, any further backspace will cause no action.
Line Deletion. The firmware
uses
the
character DEL (hex 7F) as the line deletion character.
As with the backspace character, you can program the line deletion character by using the
wce,
SF
7.
The line deletion character causes the card to delete the current line, if any. If the card is in
echoplex mode, it will write one backslash, then do a carriage-return/linefeed to indicate that the
buffer was deleted.
4-6
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