The LFEN and LFSTOP fields in the CINSTRCONF register control the operation of the custom instruction Long frame mode. Long frame mode is a mechanism that permits arbitrary byte length custom instructions. While in Long frame mode a long custom instruction sequence is split in multiple writes to the CINSTRDAT0 and CINSTRDAT1 registers.
To enable Long frame mode every write to the CINSTRCONF register must have the LFEN field set to 1. The contents
of the OPCODE field will be transmitted after the first write to CINSTRCONF and will be omitted in every subsequent write to
this register. For subsequent writes the number of data bytes as specified in the LENGTH field
are transferred (that is the value of LENGTH - 1 data bytes). The values of the LIO2 and LIO3 fields are
set in the first write to CINSTRCONF and will apply for
the entire custom instruction transmission until the long frame is finalized.
To finalize a long frame transmission, the LFSTOP field in the CINSTRCONF register must be set to 1 in the last write to this
register.