User`s manual

7-35
{
Command content
A
D
(L)
A
D
(H)
S
C
(L)
S
C
(H)
C
R
Sum check area
?
Sum check code
(4) Sum check code SC (H), SC (L)
The communication port detects error using sum check as well as party check in order to increase
the reliability.
1) Sum check area (=> Page 7-33)
● Command
2) Check method
1. Add the data in the checksum with ASCII code.
2. Convert the sum check code (2 digits hexadecimal) to 8 bits data and add to the sum of "1"
above.
When the grand total is "00(H)" (disregard figure up), the message is regarded as correct.
When the grand total is not "0," the message is regarded as an error.
3) Produce method of the sum check cord
1. Add data in the range of sum check with ASCII code.
2. Operate complement number of 2 of the result of 1.
Complement number of 2 : Turn over all the bits indicated by the binary system (0 to 1, 1 to 0)
and add 1.
[Example] The complement number of 2 of 4EHEX is B2HEX
4EHEX → 01001110
↓ Invert each bit
10110001
↓ Add 1
10110010 → B2HEX
3. Divide upper 4 bits and lower 4 bits and convert them to ASCII code.
■ When sum check code is not necessary
Put two @ signs (@ sign: 40(H)) in the checksum high and low byte positions SC(H) and SC(L)
in a command and the JW300 (control module) will not execute a checksum calculation on the
command.
Even when the @ signs are used, a checksum will still be added to the response. Please ignore
the checksums in the response if you do not need them.