uint32_ttfce:1;/*In the full-duplex mode when this bit is set the MAC enables the flow control operation to transmit Pause frames. When this bit is reset the flow control operation in the MAC is disabled and the MAC does not transmit any Pause frames. In the half-duplex mode when this bit is set the MAC enables the backpressure operation. When this bit is reset the backpressure feature is Disabled.*/