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HP 2713-0B
The host may post a read request to the card even when no receive data is available. The card will
suspend the read request until a record is received. If no read request is pending, and the card has a
record available for the host, an asynchronous event, if enabled, is sent to the host to start the read.
See the paragraph "Asynchronous Event" for additional details.
Receive Error Conditions
The firmware will terminate the current receive record when any error condition is sensed. If the "Do
Not Terminate On Error" option is set, the firmware will not terminate the record. Instead, a user-
specified replacement character will replace the bad incoming character, see the "Additional Options"
paragraph for further details.
The firmware also has the option of ignoring parity errors (process the character as if the error did not
exist), or to discard characters with any kind of error.
These errors include parity error, framing error, and data overrun.
Signal Character
When the Signal Character option is enabled, every received character is checked for a match to one
of the four signal characters, which are programmable by the user. If a match occurs, the firmware
will generate the appropriate status event.
The signal character is very similar to the use of the BREAK key on a terminal, except that you can
specify any character for this function. For example, the EM character (control- Y) may be used to in-
terru pt a program from a terminal.
If fewer than four signal characters are desired, the unused characters should be programmed as dupli-
cates of a lower-numbered used character. The search for a matching signal character proceeds from
Signal 1 to 4.
Edit Mode
Edit mode may be enabled by setting the Edit Mode option in "\\lrite Card Configuration (WCC),
Subfunction (SF) 1. Edit mode is disabled by either 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 1) when the request completes.
When working at a terminal connected to the MUX card, several types of editing capabilities are
a vailable. 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" (explained in the
"Additional Options" paragraph) allows insertion of editing characters in the text buffer without caus-
ing 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 m0dified 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.
4-5
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