Hi David:
Thanks for the information,now we have solved the problem,it's related with our product:when we reprogram the MCU,the programmer need to reset the MCU first, the MCU reset function will be active when the pin is low level,but there's another signal on the circuit board will interrupt programmer reset signal,so fail.
Now we add a circuit board to eliminate the interferen signal,now it's OK.
By the way,this no any guys in China who can support about the technical problem of this kind of MCU,suggest NXP train some agents to do this.
Thanks!
Rudy