Campbell CR23X Spécifications télécharger pdf (Page 273)

APPENDIX C. BINARY TELECOMMUNICATIONS

C-5

ABCDEFGH DATA TYPE AND SECOND BYTE FORMAT

111111XX A,B,C, = 1 - Start of Output Array, G & H are the most

significant bits of the Output Array ID. All 8 bits of the

2nd byte are also included in the ID.

XX0111XX C = 0 - First byte of a 4 byte value.

001111XX A,B = 0; C = 1 - Third byte of a 4 byte value.

01111111 A = 0; remaining bits = 1 - First byte of a 2 byte

"dummy" word. The CR23X always transmits a 0 for

the 2nd byte, but the word can be decoded on the basis

of the 1st byte only.

HIGH 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

BITS, 1ST BYTE,

1ST PAIR DESCRIPTION

CDEF = 0111 Code designating 1st byte pair of four byte number.

B Polarity , 0 = +, 1 = -.

G,H,A, Decimal locator as defined below.

2nd byte 16th - 9th bit (left to right) of 17 bit binary value.

ABCDEF = 001111 Code designating 2nd byte pair of four byte number.

G Unused bit.

H 17th and MSB of 17 bit binary value.

2nd byte 8th - 1st bit (left to right) of 17 bit binary value.

CSI defines the largest allowable range of a

high resolution number to be 99999.

Interpretation of the decimal locator for a 4 byte

data value is given below. The decimal equivalent

of bits GH is the negative exponent to the base 10.

BITS DECIMAL FORMAT

G H A 5 digits

0 0 0 XXXXX.

0 0 1 XXXX.X

0 1 0 XXX.XX

0 1 1 XX.XXX

1 0 0 X.XXXX

1 0 1 .XXXXX

C.3 GENERATION OF SIGNATURE

At the end of a binary transmission, a signature

is sent. The signature is a 2 byte integer value

which is a function of the data and the

sequence of data in the Output Array. It is

derived with an algorithm that assures a

99.998% probability of detecting a change in the

data or its sequence. The CR23X calculates

the signature using each transmitted byte

beginning with the Final Storage format data

(for K command, echo and carriage return line

feed are not included) until the 2 byte signature

itself. By calculating the signature of the

received data and comparing it to the

transmitted signature, it can be determined

whether the data was received correctly.

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