The pull-up resistor value can also be calculated from the scenario where the B-side is driving a low level. Just like the previous calculation, the pass transistor is on so current is flowing from the B-side to the A-side. Again, the RPU is normally the same on both sides and the R_DS(on) of the pass transistor can be neglected. By using the same equations as the previous page, the same pull-up resistor value can be calculated. Remember that for high-level drive from either side, the pass transistor is not conducting so the performance of the A and B sides are solely based on the value of the pull-up resistors. This is the reason that the lowest value pull-up resistor will result in the sharpest rising edge on both sides.