HP 54501A Programming Reference Manual page 46

Command Error.
A command error will be reported
if
the instrument
detects
a
syntax
error
or an unrecognized command header.
Execution Error. An
execution
error will
be
reported
if
a
parameter
is
found to be
out
of
range, or
if
the current settings do not allow execution
of
a
requested command or query.
Device-specific
Error.
A device-specific error will be reported if the
instrument
is
unable to execute
a
command for
a
strictly
device dependent
reason.
Query Error.
A
query error
will
be
reported
if
the
proper
protocol for
reading
a query
is
not followed. This includes the interrupted and
unterminated
conditions described below.
Unterminated Condition.
If
the controller attempts to read
a <
response
message
>
before terminating the
< program message
>,
a
query error
will be
generated.
The
parser
will
reset
itself, and the response will be
cleared from the output queue
of
the instrument without
being
sent over
the
bus.
Interrupted Condition.
If
the controller does not read the entire
<
response message
>
generated by
a query message
and then attempts to
send another
< program message
>,
the device
will generate
a
query
error. The unread portion of
the response
will
then be discarded
by
the
instrument.
The
interrupting
<
program message
>
will not be affected.
Buffer Deadlock. The instrument may become deadlocked
if
the input
buffer and output queue both become full.
This
condition can occur
if
a
very long
< program message
>
is
sent containing queries that generate
a
great deal of
response data.
The instrument
cannot accept any more
bytes, and the
controller
cannot
read any of the response data until
it has
completed
sending the entire
< program message
>.
Under
this
condition
the instrument will
break the deadlock
by clearing the output
queue, and continuing to discard
responses
until it comes to the end of the
current <
program message
>.
The
query error bit will
also be
set.
Message Communication and System Functions
HP 54501A
3-4
Programming