Hardware Errata and Host Driver Recovery Strategies across Die Steppings
Trap hardware stepping errata by verifying silicon ID registers during boot and driving high-side rail switches to clear frozen bus states.
Transmission Line Reflection
Signal Bounce
Voltage distortion occurs on a high-speed data path when the characteristic impedance of the conductor does not match the impedance of the load. A transmission line reflection sends a portion of the signal energy back toward the source, where it interferes with the subsequent data pulses. This phenomenon becomes critical when the signal rise time is shorter than the time it takes for the wave to travel to the end of the trace.
Wave Interference
The reflected wave combines with the original signal to create overshoot and ringing. Such a transmission line reflection reduces the noise margin and can cause a receiver to misinterpret a logic level. Keeping the trace width and the dielectric spacing consistent minimizes these unwanted bounces.
Metrological Evaluation
Time domain reflectometry identifies the exact location of an impedance mismatch along a cable or a circuit board trace. By sending a step pulse and measuring the timing of the returning echoes, an engineer can calculate the reflection coefficient. This measurement allows for the precise adjustment of termination resistors to eliminate the transmission line reflection.
Termination Type
Series or parallel resistors are placed at the ends of the line to absorb the signal energy. Correct placement prevents the energy bounce associated with a transmission line reflection.