INSTALLATfON
AND
OPERATION
The SRQ mask can
be
set to assert
SRQ when
an error is detected. The SRQ is unasserted
when the error
status is cleared.
Syntax errors are commands that do not have the correct
syntax
for the specified header.
For example, “FES” is a syntax error because the
external
FM command requires a
Boolean numeric field. Unrecognized
headers
are also syntax errors. An IEEE-488
syntax error causes all
commands
from the point of the error up to the next string
terminator or record terminator to be ignored.
Processing errors are commands that are
syntactically
valid, but the requested value is
outside the range of programmable values.
For example, “FR99GZ” is syntactically
correct, but the Generator cannot be
programmed
to a frequency of
99
gigahertz.
Command processing continues with the next
command,
2-63.
Timing
Data
The programming time can be broken down into four groups: transfer of commands to
Generator, command parsing time, software programming time, and instrument settling
time.
The total programming time depends on the selection of the interface
modes. In
some
modes, programming steps
are performed
in
parallel
and can
increase throughput. This
section
gives some
typical timing data for
the
above four
programming steps and
describes how the interface modes affect their relative timing.
2-64.
TRANSFER OF COMMANDS TO GENERATOR
The maximum rate of transfer is 0.4 to 0.5 ms per character. With most IEEE488
controllers,
all
characters
sent with a single output or print statement is transferred
together
at the
maximum
rate. The total time to transfer commands to the Generator is
obtained by multiplying the number of characters by the rate of transfer.
2-65.
COMMAND-PARSING
TIME
Command-parsing
time is the sum of the time required
to
process the header, the
numeric, and the suffix. Some commands do not
have numerics
or suffixes. Table
2-19
gives the typical time it takes to process the different
components of a command.
2-66. SOFTWARE
PROGRAMMING
TIME
The minimum time required to process a command is 20 ms. Most of the commands that
do not program the hardware (such as storing step values) are
programmed
in 20 ms.
Table 2-20 gives the typical time value for programming
the different functions in the
Generator.
2-67.
INSTRUMENT-SETTLING TIME
Commands that do not change the state
of
the hardware (such as programming step
values) have no settling time after the
software-processing
time.
For all other Generator parameters,
except
frequency and recall, the instrument has
settled
by
the time the
software-programming
time is up, so no additional instrument-
settling time is required.
Worst case frequency changes
(including recalls) typically settle within 35 ms after the
software-programming time. If level correction is disabled, this settling time is increased
to 45 ms. Small frequency changes (not crossing a band) typically settle by the time the
software-programming time
is
up, so no additional instrument-settling time is required.
2-61
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