Asynchronous Bit Bang mode is the same as BM-style Bit Bang mode. Any data written to the device in the normal manner will be self-clocked onto the data pins which have been configured as outputs. Each pin can be independently set as an input or an output. The rate that the data is clocked out at is controlled by the Baud rate generator.
For the data to change there, has to be new data written and the Baud rate clock has to tick. If no new data is written to the device, the pins will hold the last value written.