Programming
Guide
Marathon
Series
FA/FR
39
9
Programming
Guide
This
section
explains
the
sensor’s
communication
protocol.
Use
them
when
writing
custom
programs
for
your
applications
or
when
communicating
with
your
sensor
with
a
terminal
program.
9.1
Remote
versus
Manual
Considerations
Since
the
sensor
includes
a
local
user
interface,
the
possibility
exists
for
a
person
to
make
manual
changes
to
parameter
settings.
To
resolve
conflicts
between
inputs
to
the
sensor,
it
observes
the
following
rules:
•
Command
precedence:
the
most
recent
parameter
change
is
valid,
whether
originating
from
manual
or
remote.
•
If
a
manual
parameter
change
is
made,
the
sensor
will
transmit
a
“notification”
string
to
the
host.
(Notification
strings
are
suppressed
in
multidrop
mode.)
•
A
manual
lockout
command
is
available
in
the
protocols
set
so
the
host
can
render
the
user
interface
“display
only,”
if
desired.
All
parameters
set
via
the
2
‐
way
interface
are
retained
in
the
sensor’s
nonvolatile
memory.
When
a
unit
is
placed
in
multidrop
mode
its
manual
user
interface
is
automatically
locked!
It
can
be
unlocked
with
the
command
XXXJ=U
<CR>,
where
XXX
is
the
multidrop
address.
9.2
Command
Structure
Protocols
are
the
set
of
commands
that
define
all
possible
communications
with
the
sensor.
The
commands
are
described
in
the
following
sections
along
with
their
associated
ASCII
command
characters
and
related
message
format
information.
Types
of
commands
include
the
following:
1.
A
request
for
the
current
value
of
a
parameter
2.
A
change
in
the
setting
of
a
parameter
3.
Defining
the
information
contents
of
a
string
(either
continuously
output
or
periodically
polled
at
the
option
of
the
user)
The
sensor
will
respond
to
every
command
with
either
an
“acknowledge”
or
a
“not
acknowledge”
string.
Acknowledge
strings
begin
with
the
exclamation
mark
!
and
are
either
verification
of
a
set
command
or
a
parameter
value.
If
the
unit
is
in
multidrop
mode
the
3
‐
digit
address
can
be
sent
out
before
the
exclamation
mark.
For
a
change
in
the
setting
of
a
parameter,
the
range
of
possible
setting
values
is
defined,
and,
if
the
host
inputs
a
value
outside
the
allowed
range,
an
appropriate
“error”
response
character
shall
be
transmitted
back
by
the
sensor.
All
commands
must
be
entered
in
upper
case
(capital)
letters.
Also
note
that
leading
and
trailing
zeros
are
necessary!