4.21.1.2 Firmware Semaphore

This mode is useful for Ethernet driver architectures utilizing two separate threads where one thread performs configuration and management of the device, and the second thread controls Ethernet packet data transfer. The thread responsible for the transfer of data will only function once link status is true indicating that the local device is fully configured and there are other stations available for communication on the media.

When operating in this mode, the LNKSTS bit will reflect the state of the Link Status Semaphore (LSSEM) bit. By default, LSSEM is ‘0’ resulting in a false link indication at the LNKSTS bit. Once the driver management thread has configured the local device, it may set the LSSEM bit to ‘1’ resulting in a true link indication at the LNKSTS bit. The driver data thread monitoring link status can then know that local station is ready for data transfer.

Link status may conversely at any time be changed to false by clearing the LSSEM bit resulting a loss of link indication and halting the driver data thread from transferring packets.

Note, however, that in this mode of operation, link status will not indicate the availability of remote stations on the media for communication.