The DP83822 includes advanced link-down capabilities that support various real-time applications. The link-down mechanism is configurable and includes enhanced modes that allow extremely fast link-drop reaction times.
The DP83822 supports an enhanced link drop mechanism, also called Fast Link Drop (FLD), which shortens the observation window for determining link. There are multiple ways of determining link status, which can be enabled or disabled based on user preference. Fast Link Drop can be enabled in hardware with bootstrapping or in software using register configuration. RX_D2 when strapped to either mode 2 or mode 3 will enable FLD at power up or hardware reset. Additionally, FLD can be configured using the Control Register #3 (CR3, address 0x000B). Bits[3:0] and bit allow for various FLD conditions to be enabled. When link drop occurs, indication of a particular fault condition can be read from the Fast Link Down Status Register (FLDS, address 0x000F).
Fast Link Down criteria include:
The Fast Link Down functionality allows the use of each of these options separately or in any combination.
Because this mode enables extremely quick reaction time, it is more exposed to temporary bad link-quality scenarios.