Most audio commands can operate on multiple channels. The exceptions are ADCMD_WAITCYCLE, CMD_WRITE and CMD_READ, which can only operate on one channel at a time. You specify the channel(s) that you want to use by setting the appropriate bits in the ioa_Request.io_Unit field of the IOAudio block. If you send a command for a channel that you do not own, your command will be ignored. For more details, see the section on "Allocation and Arbitration" below.