DRV8811 Chopping Current setting

Hi,

   I have been working on this IC. My query regarding this device is that how does maximum value of chopping current is set? according to functional block diagram in datasheet the Rsense connected between ISENA/ISENB and Ground must be playing role in setting value of 100% value of chopping current resulting into proportional change current values in each step in Microstepping. but What I observed is totally different because even if I change value of resistor connected to between ISENx  & Ground, value of current is not affected. please solve my query.