RX Link Watchdog Timer (ctrl_rx_wdt_disable) - RX Link Watchdog Timer (ctrl_rx_wdt_disable) - 5.1 English - PG210

The RX link watchdog timer is an automatic link-recovery feature built into the 10G/25G High Speed Ethernet Subsystem. It continuously monitors whether the GT RX datapath is operational and whether PCS block lock (stat_rx_block_lock) is maintained. If block lock is lost or never achieved, an internal 750 ms countdown begins on the DRP clock (dclk). If the link does not recover within that window, the watchdog automatically issues a GT RX datapath reset to force a fresh re-initialization attempt. This repeats every 750 ms until block lock is restored.

The recovery is observed through the following existing status signals:

• stat_rx_block_lock deasserts during the reset
• stat_rx_status goes low
• user_rx_reset asserts for the duration

For example, to prevent automatic resets during PRBS testing, when a custom link management state machine is in use, or when the link partner is intentionally offline, set ctl_rx_wdt_disable to 1. This setting disables the watchdog. Access this control through AXI4-Lite register CONFIGURATION_RX_REG1[13] (address 0x0014, bit 13) when the AXI interface is enabled, or through a direct top-level input port otherwise. The default value is 0, which enables the watchdog out of reset.