Configuration

Initialization of the GMAC configuration (e.g., loop back mode, frequency ratios) must be done while the transmit and receive circuits are disabled. See the description of the Network Control register and Network Configuration register earlier in this document.

To change loop back mode, the following sequence of operations must be followed:

1. 1.Write to Network Control register to disable transmit and receive circuits.
2. 2.Write to Network Control register to change loop back mode.
3. 3.Write to Network Control register to re-enable transmit or receive circuits.

   Note: These writes to the Network Control register cannot be combined in any way.