Once the voltage difference of bitlines is a constant value which has been confirmed in the differential sense amplifier connecting with two bitlines

Once the voltage difference of bitlines is a constant value which has
been confirmed in the differential sense amplifier connecting with
two bitlines, the stored digital signal in memory cell will be output
as soon as possible. The purpose of write operation is to change the
stored logical value correctly. Therefore, before write operation, due
to the write circuitry, the voltages of bitline BL will be 0 in digital
logic. Contrary to the voltage of bitline BL, the voltage of bitline
BLN will be 1. When the voltage of WL is supply voltage VDD
(WL = 1), write operation is executed. Transistors N2, P2, P3, and
P6 are turned ON. At the moment, the states of transistors N1, P1,
P4, and P5 will be OFF, so that the logical value of this memory
cell is rightly changed to 0. Therefore, write operation can also be
completed successfully.