# Error message PLC -> CNC

Error message PLC → CNC management data
Description | This structure contains user data and data for flow control of an error message.
Data type | LC_ERROR
ST path | gpCh[channel_idx]^.lc_error
User data
Description | User data of an error message.
ST element | .satz_r
Data type | HLI_ERROR_SATZ
Access | PLC writes
Flow control of user data
Description | Validity flag of an error message.
ST element | .semaphor_rw
Data type | BOOL
Value range | [TRUE = User data is valid, FALSE]
Access | PLC sets this value to TRUE if the user data of an error message is written and therefore the error message is valid. CNC sets the value of this element to FALSE when the CNC has accepted the error message.