Festo Контроллеры двигателя SFC-LAC - Manual (Page 173)

B. Supplementary information
B−11
Festo GDCP−SFC−LACI−IO−EN en 0812NH
Checksum <PS> If checksum checking of telegrams received from the SFC−
LACI was activated (see CI object 20F3h), then the higher
level controller must also provide a checksum before the
termination character (CR = Carriage return) (for syntax,
see Tab. B/2).
If the SFC−LACI detects a deviation in the checksum, then −
instead of the usual response − the value <0xFFFF> will be
transferred (see Object 2FF0h).
The checksum of the command is calculated based on the
case (upper/lower case). The checksum of the response is
always based on upper case.
Checksum <PS>
Calculation Sum of all ASCII characters sent, reduced to 1 byte.
W:
<PS> = =IIIISS:<Value>" modulo 256
R: <PS> = ?IIIISS" modulo 256
Example:
Command =IIIISS:<Value><CR>
=20F300:00
ASCII−> = 2 0 F 3 0 0 : 0 0
HEX 3D+32+30+46+33+30+30+3A+30+30
Sum 212h
Mod 256 212h mod 100h = 12h
Response =20F300:00
12
Format 2 Hexadecimal numbers, UINT8
Tab. B/5: Checksum