Do Not Change Crc_Imp Input - Siemens SIMATIC S7 F Manual

Fail-Safe Blocks
RETVAL Parameter
Return values (RET_VAL) of the system functions are indicated at the RETVAL
parameter of the blocks for F communication. The return values are error codes
that give you additional assistance in finding the error (see the section entitled
"Error Information at the Output RETVAL").
CRC_IMP Parameter
Safety Note – Do NOT change CRC_IMP input
!
Do not make any changes to the CRC_IMP I/O because this I/O is supplied
automatically. As a result of online changes to this I/O, errors can occur during
transmission of fail-safe data when the Safety Program is executed. For example,
data may be sent to the wrong recipient or may not be recognized as coming from
an incorrect sender.
8-26
Fail-Safe Systems
A5E00085588-03