The known details about autoacking.

1) Auto-acking is disabled if promiscuous mode in enabled. Auto-acking
   is enabled when promiscuous mode is disabled. A more proper name
   for this bit would be promiscuous/#autoack.

2) If promiscuous mode is disabled and a recieved packet 1) matches
   the address filters and 2) has the ack request bit set, then an
   auto-ack will be sent (provided you do item 3 properly). The
   sequence number is stuffed and transmitted automatically. Note: you
   must have the address set properly in the maca hardware. That means
   the EUI registers for long addressing and the PANID and short
   addr. for short addressing.

3) You must wait 200 maca clocks or so after receiving a packet that
   needs an ack. This is necessary for the maca to do it's thing. If
   you don't wait enough then it either will not send the ack, or if
   you wait a little more (but not enough), the ack DSN will be zero.

4) The following must be set properly, TXACKDELAY, RXACKDELAY,
   RXEND. The best way to set these is to use a scope and the TX_ON
   and RX_ON signals. You set TXACKDELAY so that the ack is
   transmitted 12 symbols after the received packet (192 us). You set
   RXACKDELAY to start before the ack is due to arrive (I'm doing
   100us before). And you set RXEND to be long enough to receive the
   ACK (I'm doing a 700us window or so).

4b) CCA has its own set of timings.

5) The transmitter must set TXSEQNR before MACA_DMATX.

6) The status of the next "action complete" on the TX side tells you
   if the ack was received or not. Status will be 0 (success) if you
   got the ack and 5 (no_ack) if you did not.
