The transmission of the ACK frame starts 12 symbols after the end of the frame reception. The complete ACK frame is on air after 34 symbols (544us).
The internal timing for the ACK frame processing in RX_AACK mode is shown below:
== RX ==:======================= TX =========================:======= RX ======= 0 12 34 [time / symbols] +---| |---+---+---+---+---+---+---+---+---+---+---| --| F |---------|PR0|PR1|PR2|PR3|SFD|LEN| ACK | FCS |------------------> +---| |---+---+---+---+---+---+---+---+---+---+---| | | | t0 t1 t2
F = last received data byte PRx = Preamble for the ACK frame SFD, LEN, FCS = data of the ACK frame
/* TRX_IRQ_TRX_END occurs here */ frm = trx_frame_read();