# Synchronisation type (P-EXTV-00005)

P-EXTV-00005 | Synchronisation type of external variable
Description | Write/read access is normally performed synchronously with processing. In individual cases, this implicit synchronisation can be suppressed (see Access synchronisation by NC channel). If the variable is a variable structure, all subordinated structure elements inherit the synchronisation type. In addition, the synchronisation type can be individually defined for each structure element in the type definition (P-EXTV-00018).
Parameter | var[i].synchronisation
Data type | BOOLEAN
Data range | TRUE, FALSE
Dimension | ----
Default value | TRUE
Remarks | Synchronous accesses always cause the decoder to stop during a read operation until the synchronous read value is available to the decoder. In addition, it is not permitted to read synchronous variables, e.g. with functions such as an enabled Tool radius compensation; the message is output with ID 20651.