Peripherals—IP2022 User’s Manual 290 www.ubicom.com To  operate  in  USB  mode,  software  must  perform  the  following
functions: • CRC generation and checking. • Detecting reset of the device function, which is indicated by 10
milliseconds  of  a  single-ended  zero  (SE0)  condition  on  the
bus. • Detecting the suspend state, which is indicated by more than
3 milliseconds of idle. Software must make sure that the sus-
pend current of 500 µA will be drawn after 10 milliseconds of
bus inactivity. • Formation of the USB packet by putting the sync, pid, and data
into the transmit register and setting the proper count. 10Base-T Ethernet Protocol To set up a SERDES unit for 10Base-T Ethernet, the input data
from   a   differential   line   receiver   or   on-board   comparator   is
connected to the SxRXD input. The signals designated Tx+, Tx-,
TxD+, and TxD- correspond to the SxTXP, SxTXM, SxTXPE, and
SxTXME   pins   of   the   corresponding   serializers/deserializers.
These pins are connected to an RJ45 jack through a transformer
with terminations. The SxMODE register must be programmed for a recovered clock,
and   the   PLL   clock   multiplier   must   be   programmed   for   an
appropriate speed. For example, it can be programmed to be 80
MHz  for  8×  oversampling.  The  received  data  stream  is  used,
together  with  the  clock  recovery  circuit,  to  recover  the  original
transmit clock and data.