Capabilities; Receive Character Processing - HP 27130A Technical Reference Manual

HP 27130A
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CAPABILITIES
The following paragraphs provide detailed descriptions of the MUX)s capabilities.
Receive Character Processing
The receive interrupt processor is capable of offloading many of the functions usually found in the
host computer. This allows more time for the host CPU to perform other functions. The order of
processing each received character is as follows:
, c
1. If the received character has an error condition) and the "ignore parity error" bit is set in the
Write Card Configuration) Subfunction 13 (WCC, SF 13)) the parity error condition is
cleared.
2.
It
there still is an error after step 1, and the "ignore all errors" bit is set in WCC, SF 13) the
character is discarded. Otherwise) the current receive record is marked "bad". If enabled by
WCC) SF 31) the record is then made available for the host) or a substitute character is fetched to
replace the bad one and processing con tin ues.
3. If the character is a handshake character) and handshaking is enabled) check the character for an
ACK if ENQ/ ACK is enabled, or for XON or XOFF if XON/XOFF is enabled. If so) process the
character and discard it.
4.
If
the character is a signal character, and signal character detection is enabled, generate the ap-
propriate event and discard the character.
5. If the character is quotable) and quoting is enabled) check the previous character for the quoting
character. If the quoting character is present) replace it with the received character, and skip the
edi t and terminating condition checks.
6. If the character is an edit character, and edit mode is enabled) check for backspace or line delete,
and perform the edit function.
7. If the character is a single text terminator) and single text termination is enabled) terminate the
record and make it available to the host. If termination stripping is disabled) add the character to
the buffer.
If the received character does not match any of the conditions described in steps 1 through 7) the
character now is added to the current record.
8. If the end -on -count option is enabled) a check against the end -on -count is made. If the count is
exhausted, the current record is terminated with an lIend-on-count" termination.
9. If the internal card end-on-count is reached) terminate the record.
10.
If
the Alert 1 mode is enabled, generate an event to notify the host that at least one character
has been received, if this has not already been done for this record.
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