BECKHOFF EtherCAT Technology Section I - Manual (Page 113)

Process Data Interface (PDI)
Slave Controller – Technology I-93
16.3 General Purpose I/O
Some ESCs support general purpose inputs, outputs, or both. General Purpose I/O is much different
from Digital I/O, because of missing consistency and security features, and no bit-write support.
16.3.1 General Purpose Inputs
The general purpose inputs are directly mapped into the General Purpose Input registers. Consistency
of the general purpose inputs is not provided.
16.3.2 General Purpose Output
The general purpose output signals reflect the values of the General Purpose Output register without
watchdog protection. The General Purpose Output register can be written both by ECAT and PDI. The
general purpose outputs are intended e.g. for application specific LED outputs. General purpose
outputs are updated at the end of an EtherCAT frame or at the end of a PDI access.
Consistency of the general purpose outputs is not provided, and they are also not watchdog-secured.
Additionally, they do not support bit-wise modification with FMMUs.