what is Transition Time - Transistion time is the rise and fall time that is associated with signals and is sometimes called the slew rate. It can be measured using the slope of the transitioning signals in the eye diagram. A 90 degree slope implies zero transition time. In reality, there is always a certain transition time associated with rise-time and fall-time of signals, however small it may be. For DDR2 DRAM the rise and fall times is in the order of picoseconds). Smaller transition times indicate that a signal is valid for a longer time at the next time period.