If a back channel is not possible, serial channels can be initialized by driving the TX simplex initialization with a set of timers. The timers must be designed carefully to meet the needs of the system because the average time for initialization depends on many channel specific conditions such as clock rate, channel latency, skew between lanes, and noise. C_ALIGNED_TIMER, C_BONDED_TIMER, and C_VERIFY_TIMER are timers used for assertion of tx_aligned, tx_bonded, and tx_verify signals, respectively. These timers use worst-case values obtained from corner case functional simulations and implemented in the <component name>_core module.
Note: These signals are not updated on the actual status of the channel, but after the timer expires.
Some of the initialization logic in the Aurora 8B/10B module uses watchdog timers to prevent deadlock. These watchdog timers are used on the RX side of the channel, and can interfere with the proper operation of TX initialization timers. If the RX simplex module goes from aligned, bonded or verify, to reset, make sure that it is not because the TX logic spend too much time in one of those states. If a particularly long timer is required to meet the needs of the system, the watchdog timers can be adjusted by editing the module. For most cases, this should not be necessary and is not recommended.
Aurora 8B/10B channels normally re-initialize only in the case of failure. When there is no back channel available, event-triggered re-initialization is impossible for most errors because, typically, the RX side detects the failure while the condition must be handled by the TX side. The solution is to make timer-driven TX simplex modules re-initialize on a regular basis. If a catastrophic error occurs, the channel is reset and running again after the next re-initialization period arrives. System designers should balance the average time required for re-initialization against the maximum time their system can tolerate an inoperative channel to determine the optimum re-initialization period for their systems.
Note: The WATCHDOG_TIMEOUT parameter is available in the tx_channel_init_sm/
rx_channel_init_sm module to control the watchdog timers present in the channel initialization process.