DRV8462: Customizable micro-stepping table operate under 1/256 micro step mode

I use DRV8462 to design our precision motion control system. it is working well. the only issue is Customizable micro-stepping.  

I load the customized number into register 0x17-0x1E.  

when I set EN_CUSTOM to 0 

if  write 0xFA into  register 0x05 , will cause motor move forward 1/256 step.    (register 0x11  number increase/decrease 1 step)

the write 0xF5 into  register 0x05 , will cause motor move forward 1/8 step.     (register 0x11  number increase/decrease 32 steps)

MICROSTEP_MODE [3:0] works

but, if I set  EN_CUSTOM to 1 

No matter what MICROSTEP_MODE I selected. 

write 0xFA or 0xF6 or 0xF0 into  register 0x05 ,  the motor always move forward 1/8 step.    (register 0x11  number will turn to same as the CUSTOM_CURRENTx value)

is it possible to make DRV8462  able to support 1/256 micro-step mode using a Customizable micro-stepping table?