MCU-PLUS-SDK-AM243X: Stop in "Flash SOC Initialization Binary"

when I try to "Flash SOC Initialization Binary",follow the "AM243x MCU+SDK 09.01.00"-> Gettin Started -> EVM Setup

I had make sure boot mode setting for  UART BOOTMODE, but the python script 

BOOTMODE [ 1 :  8 ] (SW4) = 1110 0000

' python uart_uniflash.py -p COM5 --cfg=sbl_prebuilt/am243x-lp/default_sbl_null.cfg '

always stuck in step 2.

any advice?