A set of eight 12-bit registers to store the most recent ADC data. Also includes a demultiplexer to select which register to write to. In practice there is a 16-bit-wide bus on output: the 12-bit data is pre-padded with zeros for the convenience of other modules.
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A set of 12 8-bit registers to store the board's and PC's MAC addresses (in that order). Note that all bits of the register are set high upon reset as a simple way to ensure that packets sent to the PC before its address has been learned will be interpreted as a broadcast packet.