FT2232HL - using FIFO to send continous data to processing + signaling information
There are several ways to approach this.
If you have only a small number of simple commands, then you can &quot;reserve&quot; some of the DAC data values for those commands. Obviously, this decreases the dynamic range of your signal very slightly.
A more general approach is to introduce a packet structure to the data. A header byte tells you what kind of packet you're sending — a short command packet or a long DAC data packet — and the FPGA does the right thing with each kind of packet.
Of course, you can do the same thing in the other direction, too.