Operator`s manual

SECTION 5. TELECOMMUNICATIONS
5-2
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 all characters 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.g., 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. If 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 all the 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. If 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 described
in the following Table. The Data Storage Pointer
(DSP) and Telecommunications Modem Pointer
(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
#1 is the number of E08 and #2 is the number of overrun that have occurred
(cleared by entering 8888A); Memory status, the decimal number (in ASCII
characters) that is the equivalent of the 8 bit binary number shown as the
result of the memory check on power-up; Location of MPTR; and Checksum.
All in the following format:
R+xxxxx F+xxxxx Vx Exx xx Mxxxx L+xxxxx Cxxxx
If 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