Festo CPX System Manual page 220

C. General information on parametrisation
C−22
Mode of operation
With the CPX terminals the start and end of a fault can be
protocolled in the internal diagnostic memory. The diagnostic
memory contains up to 40 entries. In addition to information
on localising the fault, the relevant time point is saved,
measured from the moment the power supply is switched on.
A diagnostic entry consists of 10 bytes. The first five bytes
contain information on the time point. The last five bytes con
tain information on the fault (see section B.2.5).
With the aid of the function number, entries in the diagnostic
memory can be read out via the I/O diagnostic interface irre
spective of the fieldbus protocol used. The various fieldbus
protocols provide, where applicable, further possibilities for
reading out and configuring the CPX diagnostic memory (see
the manual for the specific CPX bus node).
Festo P.BE−CPX−SYS−EN en 0902e