"Hello everyone! BGU8051 used in TDD mode, if you want to achieve BGU8051 in a normally open state, pin 6 of the voltage is 0V or 2V, or with a rectangular square wave control, hope that the chip used to give guidance to the people!"
Please look at the Table 8, Shutdown control in the BGU8051 Datasheet http://www.nxp.com/documents/data_sheet/BGU8051.pdf
On state - < 0.6V on Pin 6 (SHDN)
Off state - > 1.2V on Pin 6 (SHDN)
