Subversion Repositories miniuart2

This testbench will simulate a BitStream on the RxD pad. The RxUnit unserialise it and
store it in the receive register.

at 17.2uS, the RxD line is driven low. This is the start bit.
from 34.4uS to 139.2uS follows the others bits from 0 to 7.
at 139.2uS the RxD line is driven high. This is the stop bit.
at 173.6uS the intrx_o signal goes high. This indicates that a byte has been received by
   the Rx unit.
at 190uS the status reg is read (adr 01). It contains the value 0x03. This indicates that
   a char is available in the receive register (bit1 = 1).
at 200uS the receive buffer is read. It contains the value 0x32.
The baudrate is 57600bps.