Instruction Manual

A-14

Appendices

6 Calculating Checksums

A checksum can be appended to read data as it is being transmitted (The checksum will not be

appended to commands or replies).

The checksum allows you to check if RS-232C communications have become corrupted. By

using the PASS/RTRY or ACK/NAK protocols, an automatic RTRY or can be sent if the

checksum does not match. Settings should be handled through "Protocol settings" on the setting

software (This cannot be done when using a PLC link).

Checksum calculation range and location

The checksum is calculated using all characters that are not a part of the header or the delimiter

and is then appended immediately after the delimiter.

CC= checksum (2 ASCII characters)

• When an ID number is appended

• When an ID number is not appended

NAK

P mm -Header Read data% Delimitercc

P 01 -Header ERROR% Delimitercc

nnnn

0009

Header Read data Delimiterccnnnn

Header AB12 Delimitercc0004