User Manual

C. CI interface
C−10
Festo GDCP−SFC−LACI−DN−EN en 0812NH
Error messages If there are errors in the commands (e.g.syntax errors,
transmission errors), the value <0x00FF> will be transmitted
(object 2FF0h) instead of the
usual reply. Possible causes:
 Incorrect initial character, separating character or empty
character
 Incorrect hex digit
 Incorrect value type
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 prov
ide a checksum before the
termination character (CR = Carriage return) (for syntax, see
Tab.C/2).
If the SFC−LACI detects a deviation in the c
hecksum,
then  instead of the usual response  the value <0xFFFF> will
be transferred (see Object 2FF0h).
The checksum of the command is calculated based o
n 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 =20F300:0012
Format 2 Hexadecimal numbers, UINT8
Tab.C/5: Checksum