Help: ICE_KEYS_MPCIO

Multi-Purpose Chip I/O register.

This register controls the 4-bit multi-purpose chip I/O bus.  
The bottom 4 bits are the data values. The upper 4-bits are their respective output enables.
On the ICEPOD-6 the bits are as follows:
  0: UID Chip clk
  1: UID Chip data
  2: USB 0 data/power enable
  3: USB 1 data/power enable