XCPU Mode

In XCPU mode the GPIO pads take on the previously defined functions necessary to interface to the external CPU. Off-chip circuitry is required to perform the remaining GPIO functionality. This circuitry implements the "Operation Registers" described above. The "Configuration Registers" are not implemented in the off-chip circuitry. It is assumed that the configuration is constant for each machine type, and therefore can be hard wired in the off-chip hardware.

The exception to the above is that the GPIO[24:26] pads remain unchanged and their configuration registers function internally in XCPU mode.