Checksum - Ulvac G-TRAN Series Instruction Manual

Checksum

The checksum is for checking whether the data is received normally. If the checksum is
not added, this unit will not be able to receive the command.
The checksum calculation is Xor(exclusive OR) from the address to the character before
the checksum.
When calculating the checksum manually, it is convenient to use the Windows standard
"calculator." Select either a scientific calculator or a programmer calculator, and
calculate in hexadecimal.
Example：When reading the measurement value and the status of address 11.
The command and ASCII code to read the measurement value and the status
of address11 are as follows:
Command
(ASII)
HEX
「31」 Xor 「31」 Xor 「44」 = 4
The calculation by XOR from the address to the character before the checksum is
44. Do not calculate the first character ":" of the command.
Therefore, the correct command is:
Command
(ASII)
When the measurement value at this time is the following:
Command
: 1 1
(ASII)
↓ ↓
HEX 31 31
「31」 Xor 「31」 Xor 「44」 Xor 「31」 Xor 「2E」 Xor
「30」 Xor 「30」 Xor 「45」 Xor 「2B」 Xor 「30」 Xor
「35」 Xor 「46」 Xor 「36」
=「40」
Therefore, the calculation by XOR from the address to the character before the
checksum is "40", which means that the data was received normally.
Do not calculate the first character ":" of the command.
: 1 1
↓ ↓
31 31
: 1 1
D 1 . 0 0
↓ ↓ ↓ ↓ ↓
44 31 2E 30 30
D CHKH CHKL
↓
44 CHKH CHKL
D 4
E + 0 5 F
↓ ↓ ↓ ↓
45 2B 30 35 46
43
CR
CR
4 CR
6 4 0 CR
↓
36 CHKH CHKL CR