Two important timing specifications are pulse skew and part-to-part skew. Pulse skew is the magnitude of the difference of rising edge propagation delay to falling edge propagation delay: tSKEW = |tPLH - tPHL|. It determines the maximum possible pulse distortion that is from a single-ended input pulse to a differential output pulse for a driver, and from a differential input pulse to a single-ended output pulse for a receiver. Part-to-part skew is the skew between any two units tested with identical test conditions (temperature, VCC, etc.). This parameter is especially important in synchronous applications, where the clock and data signals come from different transceivers requiring a low part-to-part skew in order to maintain the clock-to-data timing. Note: because of the precise switching characteristics of Renesas transceivers due to very low process variations, Renesas is the only vendor of high speed RS-485 transceivers that specifies a maximum part-to-part skew.