The output DATA channel can be configured to have no TLAST, to have vector framing, to have packet framing, or to have a TLAST that is configuration triggered.
When set to Vector Framing, TLAST is asserted for the transfer that contains the TDATA of the last TDM channel of a cycle of TDM channels (for example, channel 12 of 12).
When set to Packet Framing, the TLAST of the input PHASE channel is passed unaltered with latency equal to the latency of the main datapath. This is intended to be a service to the system designer, where TLAST might have a meaning which is irrelevant to the DDS, but relevant to some core downstream.
When set to Configuration Triggered, the TLAST is generated internally by the DDS rather than conveyed from the input PHASE channel. It is asserted on the last channel of a TDM cycle immediately before a configuration change is effected. In other words, if a configuration change is provoked using the CONFIG channel, TLAST is asserted on the last sample of the old configuration.