Keypad Lock (Block The Access To The Instrument); 10. Keypad Unlock; 11. Display And Keypad Lock; Check-Sum Calculation - LAUMAS TLU Installation And User Manual

9.

KEYPAD LOCK (BLOCK THE ACCESS TO THE INSTRUMENT)

The PC transmits the following ASCII string: $aaKEYckckCR
Possible instrument responses:
- correct reception: &&aa!\ckckCR
- incorrect reception: &&aa?\ckckCR

10. KEYPAD UNLOCK

The PC transmits the following ASCII string: $aaFREckckCR
Possible instrument responses:
- correct reception: &&aa!\ckckCR
- incorrect reception: &&aa?\ckckCR

11. DISPLAY AND KEYPAD LOCK

The PC transmits the following ASCII string: $aaKDISckckCR
Possible instrument responses:
- correct reception: &&aa!\ckckCR
- incorrect reception: &&aa?\ckckCR

12. CHECK-SUM CALCULATION

The two ASCII characters (ckck) are the representation of a hexadecimal digit in ASCII
characters. The check digit is calculated by executing the operation of XOR (exclusive or) of 8-bit
ASCII codes of only the string underlined.
The procedure to perform the calculation of check-sum is the following:
- Consider only the string characters highlighted with underlining;
- Calculate the EXCLUSIVE OR (XOR) of 8-bit ASCII codes of the characters;
Example:
character
0
1
t
XOR =
- The result of the XOR operation expressed in hexadecimal notation is made up of 2 hexadecimal
digit (that is, numbers from 0 to 9 or letters from A to F). In this case the hexadecimal code is
0x75.
- The checksum is made up of the 2 characters that represent the result of the operation and XOR
in hexadecimal notation (in our example the character " 7 " and the character " 5 ").
decimal ASCII code
48
49
116
117
hexadecimal ASCII code
30
31
74
75
- 27 -
binary ASCII code
00110000
00110001
01110100
01110101