Method and apparatus for controlling an operating mode for an embedded Ethernet media access controller

A method of controlling an operating mode of an Ethernet media access controller (MAC) embedded in a programmable device, comprising:

• receiving a configuration signal from configuration memory of the programmable device and a host signal from a host bus of the programmable device;
• generating a control length check disable signal the value of which depends on the value of at least one of the configuration signal and the host signal, wherein the generating a control length check disable signal comprises:
• storing a value for the control length check disable signal in a register;
• selecting one of the host signal or the control length check disable signal as a first output signal in response to an enable signal of the Ethernet MAC;
• and
• selecting one of the configuration signal or the first output signal as an input to the register in response to a reset signal of the Ethernet MAC;
• deriving a control signal from at least one of the control length check disable signal and the configuration signal;
• and
• selectively disabling checking a length of each control frame in frames received by the Ethernet MAC based on a value of the control signal.

A programmable device, comprising:

• an Ethernet media access controller (MAC) having a receive client interface for providing frames as output;
• a receive client circuit, coupled to the receive client interface, for processing the frames;
• a configuration memory having a storage location storing a value of a configuration signal coupled to the Ethernet media access controller;
• a host controller coupled to a host bus that provides a host signal to the Ethernet media access controller;
• a configuration circuit configured to receive the configuration signal and the host signal, and further configured to output a control length check disable signal the value of which depends on the value of at least one of the configuration signal or the host signal, wherein the configuration circuit comprises:
• a register configured to provide the control length check disable signal;
• a first multiplexer configured to select one of the host signal or the control length check disable signal as a first output signal in response to an enable signal of the Ethernet MAC;
• and
• a second multiplexer configured to select one of the configuration signal or the first output signal as an input to the register in response to a reset signal of the Ethernet MAC;
• and
• a parameter check circuit configured to receive a control signal derived from at least one of the control length check disable signal or the configuration signal and to provide a frame length error signal to the receive client circuit, and
• further configured to selectively disable checking a length of each control frame in the frames received by the Ethernet MAC based on a value of the control signal.