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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.
The
following
paragraphs
give
some
typical
timing data
for the
above
four
programming
steps
and
describes
how
the interface
modes
affect their relative
timing.
2-66.
TRANSFER OF
COMMANDS
TO GENERATOR
The
maximum
rate
of
transfer
is
0.4
to 0.5
ms
per
character.
With most IEEE-488
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.
2-67.
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-
1
9 gives
the typical
time
it
takes
to
process the
different
components
of a
command.
2-68.
SOFTWARE PROGRAMMING
TIME
The
minimum
time required
to
process a
command
is
25 ms.
Most
of the
commands
that
do
not
program
the
hardware
(such
as
storing step values) are
programmed
in
25 ms. Table 2-20
gives the typical
time value
for
programming
the different functions
in
the
Generator.
2-69.
INSTRUMENT-SETTLING TIME
The
software-programming
time
typically
exceeds
the
setting
time
of the
RF
circuitry,
therefore the instrument-settling time
can
generally be
excluded
from throughput
calculations.
The
exception
is
when
level
correction
is
disabled.
Disabling
level
correction reduces the
software-programming
time by
10
ms
but does not
affect
the
switching time of the
frequency
programming
circuitry.
A
10
ms
settling
delay should be
added
if
level
correction
is
disabled
and
a
settled
RF
output
is
required.
2-70.
TIMING OPTIMIZATION
Timing depends upon
the interface
modes
selected.
Refer
to
the
paragraphs
on
Interface
Mode
Commands
for
a
complete
description
of the
interface
modes.
The
transfer of
commands
from
the
IEEE-488
controller
to
the
Generator can
never be
processed
in
parallel
with anything
else.
The
transfer of
commands
usually
happens
simultaneously,
regardless of
which
interface
mode
is
selected.
The
parsing
of the
command
and
programming
the
new
instrument
state
is
performed one
message
unit
at
a time.
The
record
mode
selects
a
command
or
a
record
as
the
message
unit.
The
record
mode
off
("RMO")
is
slower
since there
is
extra processing
between message
units,
and
the
message
unit
is
smaller.
If
the valid
mode
is
enabled,
the
processing of
message
units
is
delayed
until
the
Generator has
settled
from
the
previous message.
While
the
RF
output
is
typically settled
before
the
software
finishes
processing the
command,
enabling
the
valid
mode
adds an
additional delay
to
ensure
that the
output
is
settled
before the
next
command
is
processed.
If
the
output
of the
Generator does not need
to
be
settled
between
programming
strings,
the
valid
mode
should be turned
off to
speed
up
processing.
If
the
output does not need
to
be
settled
between
commands,
but
needs
to
be
settled
between
records,
enable
the valid
mode
and
the
record
mode.
The
instrument processes
commands
within the record
as
fast as
possible
and
waits for the
output
to
settle
only
between
records.
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