Campbell 21X Manuel de l'opérateur télécharger pdf (Page 172)

APPENDIX

C.

BINARYTELECOMMUNICATIONS

HIRESOLUTION

FORMAT

Continuing

to use the A-H

bit

representation,

the four

byte

number

is

shown

below

as two two

byte

pairs.

ABO111GH

XXXXXXXX

OO1111GH XXXXXXXX

BITS,

1ST BYTE,

lST

PAIR

CDEF=0111

B

G,H,A,

2nd

byte

ABCDEF=001111

G

H

CAMPBELL

SCIENTIFIC

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.

DESCRIPTION

Code

designating

1st

byte

pair

of four byte

number.

Polarity,0=+,

1=-.

Decimal

locator

as defined

below.

16th

-

gth

bit

(left

to

right)

of 17

bit binary

value.

Code designating 2nd

byte

pair

of four byte number.

Unused bit.

17th and MSB

of 17 bit binary value.

8th

-

1st bit

of 17

bit bina

BITS

GHA

000

001

010

011

100

101

DECIMAL FORMAT

5 digits

XXXXX.

XXXX.X

XXX.XX

XX.XXX

X.XXXX

.XXXXX

signature

of

the received

data and

comparing it

to

the transmitted

signature, it can be

determined whether the

data

was received

correctly.

SIGNATURE ALGORITHM

51,S0 represent

the

high and

low

bytes of the signature,

respectively

M represents

a transmitted

data

byte

represents

the existing

byte

represents

the

new

byte

represents

a temporary

represents

the carry

bit

from a

shift operation

1. The

signature is

initialized

with both

bytes

set

to hexadecimal AA.

S1(n)=Ss(n)=44

2. When

atransmitted byte, M(n+1), is

received,

form a

new high signature

byte

setting

it equal to

the existing

low

byte.

Save

the old

high

byte

for later use.

n

n+1

T

c

C.3

GENERATION

OF SIGNATURE

At

the end of abinary

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.

lt is

derived

with an

algorithm

that assures

a

99.998%

probability

of detecting

a change in the

data

or its

sequence. The 21X

calculates

the

signature

using each

transmitted

byte except

the 2

byte signature

itself.

By

calculating

the

c-4

1 2 ... 167 168 169 170 171 172 173 174 175 176 177 ... 190 191

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