If sleep enable is set, the PHY transitions to sleep mode after the MDI line goes silent when in sleep_silent state; however, if sleep enable is not set, the device transitions to standby after the MDI line goes silent. By default, sleep enable is set. Once in sleep mode, all PHY blocks are disabled except for energy detection on the MDI. All register configurations are lost in sleep mode. No link can be established, data cannot be transmitted or received and SMI access is not available when in sleep mode.