Manual

SECTION 5. TELECOMMUNICATIONS
5-2
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
CR7 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 CR7 sends ASCII data with eight data bits,
no parity, plus one start bit and one stop bit.
After answering a ring, or completing a
command, the CR7 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 CR7 "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 CR7 in telecommunications,
the CR7 counts all the invalid characters it
receives from the time it answers a ring, and
terminates communication after receiving 150
invalid characters.
The CR7 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 CR7 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 CR7 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. CR7
sends the MPTR Location and Checksum: L+xxxxx Cxxxx