FLT
I2C Programmable Filter Factor
Controls the width of the glitch, in terms of I2C module clock cycles, that the filter must absorb. For any
glitch whose size is less than or equal to this width setting, the filter does not allow the glitch to pass.
0h No filter/bypass
1-Fh Filter glitches up to width of n I2C module clock cycles, where n=1-15d

这个是抑制I2C总线上的抖动用的，至于是SCL还是SDA上的抖动手册上没有说。
以I2C模块的时钟为基准，设定一定的时钟周期，滤除掉总线上的抖动。