Campbell Scientific CR7 Measurement and Control System - Manual (Page 168)

APPENDIX C. BINARY TELECOMMUNICATIONS
C-4
to the telecommunications F command a 2 byte
signature is sent (see below).
Representing the bits in the first byte of each
two byte pair as ABCD EFGH (A is the most
significant bit, MSB), the byte pairs are
described below.
LO RESOLUTION FORMAT - D,E,F, NOT ALL
ONES
BITS DESCRIPTION
A Polarity, 0 = +, 1 = -.
B, C Decimal locators as defined below.
D-H plus 13 bit binary value (D=MSB).
second Largest possible number without D,
E, and F all 1 is 7167,
byte but CAMPBELL SCIENTIFIC
defines the largest allowable range
as 6999.
The decimal locators can be viewed as a
negative base 10 exponent with decimal
locations as follows:
B C Decimal Location
0 0 XXXX.
0 1 XXX.X
1 0 XX.XX
1 1 X.XXX
DATA TYPE WHEN D,E,F, ALL EQUAL ONE
If D, E, and F are all ones, the data type is
determined by the other bits as shown below. X
implies a "don't care" condition; i.e., the bit can
be either 1 or 0 and is not used in the decode
decision.
A B C D E F G H DATA TYPE AND SECOND BYTE FORMAT
1 1 1 1 1 1 0 X A,B,C, = 1 - Start of output array, G=0. H is the most significant bit
of the output array ID. All 8 bits of the 2nd byte are also included in
the ID.
X X 0 1 1 1 X X C = 0 - First byte of a 4 byte value.
0 0 1 1 1 1 X X A,B = 0; C = 1 - Third byte of a 4 byte value.
0 1 1 1 1 1 1 1 A = 0; remaining bits = 1 - First byte of a 2 byte "dummy" word. The
CR10 always transmits a 0 for the 2nd byte, but the word can be
decoded on the basis of the 1st byte only.
HI RESOLUTION FORMAT
Continuing to use the A-H bit representation, the four byte number is shown below as two two byte pairs.
AB0111GH XXXXXXXX 001111GH XXXXXXXX