Rice Lake Signal Conditioning Transmitter/Indicators - Manual (Page 60)

56 SCT Weight Transmitter Operator’s Manual
Keypad Lock (Access Protection To The Instrument)
The PC transmits: $aaKEYckckCR
$01KEY56CR
Possible instrument responses:
- correct reception: &&aa!\ckckCR
- incorrect reception: &&aa?\ckckCR
Keypad Unlock
The PC transmits: $aaFREckckCR $01FRE50CR
Possible instrument responses:
- correct reception: &&aa!\ckckCR
- incorrect reception: &&aa?\ckckCR
Display And Keypad Lock
The PC transmits: $aaKDISckckCR
$01KDIS14CR
Possible instrument responses:
- correct reception: &&aa!\ckckCR
- incorrect reception: &&aa?\ckckCR
Check-Sum Calculation
The two ASCII control characters (ckck) are the representation of a hexadecimal digit in ASCII characters. The
check digit is calculated by performing the operation XOR (exclusive or) 8-bit ASCII codes of the only part of the
underlined string.
The procedure to calculate the check- sum is the following:
• Consider only the string characters highlighted with underlining;
• Calculate the EXCLUSIVE OR (XOR) of the ASCII codes for the characters;
Example:
• The result of the XOR operation expressed in hexadecimal notation is made up of 2 hexadecimal digits
(numbers from 0 to 9 or letters from A to F). In this case the hexadecimal code is 0x75.
• The check-sum inserted in the strings transmitted is made up of the 2 characters which represent the result of
the XOR operation in hexadecimal notation (in our example the character " 7 " and the character " 5)
Character Decimal ASCII Code Hexadecimal ASCII Code Binary ASCII Code
0 48 30 00110000
1 49 31 00110001
t 116 74 01110100
XOR = 117 75 01110101