dynamixel AX-12 lib - porting to ESP8266

I want to port the AX12 library from Michael E. Ferguson/Pablo Gindel to the ESP8266.

I could need some help/docu pointers for handling the serial port. Does it have a HW buffer, and which size? How can I programm it to behave 1 Mbps halfduplex?

May I find some help here in the ardu forms?

Now I have found some very good docu rigth at the vendors pages:

Especially this doc about the UART:
http://espressif.com/en/file/382/download?token=BpQnPCLI

But still their explanations are a bit unclear. There is one 128 byte FIFO for rx and tx all together. Does it mean, if I send 150 byte at once, then there will be no space to (queue-)receive rx, until the first 22 bytes or so are sent out?