auto-RTS (see Figure 1)
Auto-RTS data flow control originates in the receiver timing and control block (see functional block diagram) and is linked to the programmed receiver FIFO trigger level. When the receiver FIFO level reaches a trigger level of 1, 4, 8, or 14 in 16-byte mode or 1, 16, 32, or 56 in 64-byte mode, RTS is deasserted. The sending ACE may send an additional byte after the trigger level is reached (assuming the sending ACE has another byte to send) because it may not recognize the deassertion of RTS until after it has begun sending the additional byte. RTS is automatically reasserted once the receiver FIFO is emptied by reading the receiver buffer register. The reassertion signals the sending ACE to continue transmitting data.

auto-CTS (see Figure 1)
The transmitter circuitry checks CTS before sending the next data byte. When CTS is active, the transmitter sends the next byte. To stop the transmitter from sending the following byte, CTS must be released before the middle of the last stop bit that is currently being sent. The auto-CTS function reduces interrupts to the host
system. When flow control is enabled, the CTS state changes and does not trigger host interrupts because the device automatically controls its own transmitter. Without auto-CTS, the transmitter sends any data present in the transmit FIFO and a receiver overrun error can result.