Jitter is the variation in arrival time of data. In non-packet based digital systems, there is a similar phenomenon known as 'ragged edge triggers'. In a 16 bit system, all bits have to fire (trigger) within a very short window. Chips are rated in part for speed based largely on how narrow that window is. How long it takes that bit to rise from nominal 0 to nominal 1 is the rise time. Chips with large variations in trigger and rise time are considered 'ragged' and only suitable for slow and undemanding applications. Not surprisingly, cheap chips tend towards 'ragged'. G