I wiil DIY a develop board like MCB2130 ,I don't kown what it is the function of ETM.Is it must need in this board? thanks
"I don't kown what it is the function of ETM. Is it must need in this board?" It's part of the chip - whether you think you "need" it or not! You need to study the Datasheet carefully before designing-in any chip! http://www.keil.com/dd/chip/3648.htm