HP 271308 Technical Reference Manual page 72

HP 27130B
NOTE
If you should change any of the read termination para.,.
meters, such as text termination, end -on -count, and so
on, the new parameters will not affect any text record
that has already been terminated. If the frontplane has
an active receive record, the text termination conditions
will become active after the current record is ter-
minated. Otherwise, the new parameters will become ef-
fective immediately.
In echoplex mode, if a transmit record is active, any incoming characters will be echoed after the
transmit record is empty. This should prevent incoming characters from interrupting any outgoing es-
cape sequences which are either less than or equal to 252 bytes.
It
will not, however, prevent a write
from interrupting an escape sequence being echoed from the receiver, or if software handshaking is
enabled, the handshake characters will not be prevented from interrupting any outgoing text.
NOTE
THE MUX CARD HAS A 128-BYTE ECHO BUFFER
FOR EACH PORT. IF THIS BUFFER SHOULD
OVERFLOW, ECHO INFORMATION WILL BE LOST,
AL THOUGH THIS WILL NOT AFFECT ANY
RECEIVE TEXT BUFFERS. AN OVERFLOW CAN BE
CAUSED BY THE CARD RECEIVING MUCH DATA
AFTER HAVING RECEIVED A DEVICE X-OFF, OR
NOT YET HAVING RECEIVED AN ACK TO A HOST
ENQ.
Character echoing is enabled by setting the echo bit in the data block of the WCC, SF 1. Character
echoing may be toggled (on or off) for the duration of the request by setting the "toggle echo" bit in
the subfunction. Echoing is only available for full-duplex transmission mode.
The card will not echo single text termination characters. However, the card can be enabled to echo a
CR/LF for every CR received as a single text terminator by setting the lIecho CR-LF for CR text ter-
minator" in the data block of the WCC, SF
9.
By using the WCC, SF 27, you may select which single
text terminator in place of the CR to cause the CR-LF echoing.
Receiving Transparent or Binary Data
Transparent, or binary, data are defined to be data read with no processing by the firmware. The data
are always terminated by using the End -On -Count option. All special processing such as software
handshake, edit mode, and single text termination should be <l:isabled. This may be done either by
changing the read configuration in WCC, SF
27;
or by setting the read device data request subfunction
bits "toggle edit", "toggle signal", and "toggle quoting" as necessary.
Note that data errors (parity, framing, overflow) will terminate the record unless specifically disabled
(WCe, SF 31).
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