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SECTION
5.
TELECOMMUNICATIONS
5.
CR to
datalogger means "execute".
6.
CRLF from
datalogger means "executing
command".
7.
ANY character besides a CR sent to
the
datalogger
with a legal command in
its
buffer causes
the datalogger to abort the
command sequence
with CRLF* and to zero
'the command
buffer.
8.
All
commands return a response code,
usually at least
a
checksum.
9.
The
checksum includes allcharacters sent
by
the datalogger since
the last *, including
the echoed command sequence, excluding
only the
checksum
itself.
The
checksum
is
formed by summing the ASCII values,
without parity,
of
the transmitted characters.
The largest possible checksum value
is
8191.
Each time
8191
is
exceeded, the 21X
starts the count over;
e.9.,
if
the sum
of
the
ASCII values is 8192, the checksum is
0.
10. Commands that return Campbell Scientific
binary
format data
(F
and
K
commands)
return a
signature (Appendix
C).
The 21X sends ASCII data with 8 data bits,
no
parity, plus one start bit and one stop
bit.
After answering
a ring,
or
completing a
command, the 21X waits about 40
seconds (147
seconds
in
the Remote Keyboard State) for
a
valid character to
arrive.
lf
a
valid character
is
not received, the
21X "hangs
up".
Some
modems are quite noisy
when
not
on line; it
is
possible for valid characters
to appear
in
the
noise
pattern. To
insure that this situation does
not keep the
21X
in
telecommunications, the
21X counts
allthe
invalid characters it receives
from the
time
it
answers
a ring, and terminates
communication
after receiving 150 invalid
characters.
The 21X continues to
execute its measurement
and processing tasks while servicing
the
telecommunication
requests.
lf
the processing
overhead is large (short
execution interval), the
processing tasks will slow
the
telecommunication
functions.
In
a worst case
situation, the
21X interrupts the processing
tasks to transmit a data point every 0.1 second.
The best way to become familiar with the
Telecommunication Commands
is
to
try them
from
a
terminal connected to the 21X via the
SC32A or
other modem interface (Section 6.5).
Telecommunications
Commands
are
in
the following
Table. The
Data Storage
(DSP) and
Telecommunications Modem Pointe
(MPTR) referred
to
in
the table are described
in
Section 2.1.
TABLE
5.1-1. Telecommunications Commands
Command
Description
A
STATUS - Datalogger returns Reference, the DSP location; the number
of
filled Final Storage locations; Version of datalogger; Errors #1 and #2 where
r"1J:,'J;#H:i,:l='33trif;,',#:l:#il:1"J;::,'fi
Iffi l:ff
itffi
'
characters)that
is
the equivalent
of
the 8 bit binary number shown as
the
fiillf:,l:fr:fffl.#fk
on power-up; Location of
MPrR;and
checksum.
R+xxxxx F+xxxxx Vx Exx xx Mxxxx L+xxxxx Cxxxx
lf
data are stored
while
in
telecommunications, the A
command must
be
issued
to update the Reference to the new
DSP.
[no. of
arrays]B
BACK-UP - MPTR is backed-up the specified number of output
arrays
(no
number defaults
to 1) and advanced to the nearest start of
array.
21X sends
the MPTR Location and Checksum: L+xxxxx Cxxxx
5-2
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