Generation Of Signature; B.3 Generation Of Signature; D Commands To Transfer Program With Computer - Campbell CR510 Operator's Manual

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
G H A
0 0 0
0 0 1
0 1 0
0 1 1
1 0 0
1 0 1

B.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 CR510 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.
SIGNATURE ALGORITHM
S1,S0 - represent the high and low bytes of
the signature, respectively
M - represents a transmitted data byte
n - represents the existing byte
n+1 - represents the new byte
T - represents a temporary location
C - represents the carry bit from a shift
operation
1. The signature is initialized with both bytes
set to hexadecimal AA.
S (n) = S
1
2. When a transmitted byte, M(n+1), is
received, form a new highsignature byte by
setting it equal to the existing low byte.
Save the old high byte for later use.
T
S (n+1) = S
1
DECIMAL FORMAT
5 digits
XXXXX.
XXXX.X
XXX.XX
XX.XXX
X.XXXX
.XXXXX
(n) = AA
0
= S (n)
1 1
(n)
0
APPENDIX B. BINARY TELECOMMUNICATIONS
3. Form a temporary byte by shifting the old
low signature byte one bit to the left and
adding any carry bit which results from the
shift operation. A "shift left" is identical to a
multiply by 2. Ignore any carry bit resulting
from the add.
T = shift left (S
2
4. Form the new low signature byte by adding
the results of operation 3 to the old high
signature byte and the transmitted byte.
Ignore any carry bits resulting from these
add operations.
S (n+1) = T
0
As each new transmitted byte is received, the
procedure is repeated.
B.4 D COMMANDS TO TRANSFER
PROGRAM WITH COMPUTER
D Commands 1 and 2 (when entered from the
Keyboard/Display) and 7 have an additional 2 digit
option parameters (7 is entered with the Storage
Module address, e.g., 71). The CR510 will
display the command number and prompt for the
option. If the keyboard display is not being used,
the CR510 will have already set the baud rate to
that of the device it is communicating with and will
be ready to send or receive the file as soon as
command 1 or 2 is entered.
TABLE B.4-1. D Command 1 and 2 Options
Command
1 & 2 1x
4x
After the option code is keyed in, key "A" to
execute the command. Command 2 will be
aborted if no data is received within 40 seconds.
WHEN COMMAND 2 IS EXECUTED ALL
DATA IN INPUT AND INTERMEDIATE
STORAGE ARE ERASED. This section
describes commands 1 and 2.
(n)) + carry
0
+ S (n) + M(n+1)
2 1
Option Code Description
Synchronously addressed
Hardware enabled
x = Baud Rate Codes
0 - 300
1 - 1200
2 - 9600
3 - 76,800
B-5