Peripherals—IP2022 User’s Manual 288 www.ubicom.com line  is  activated  before  responding.  In  master  mode,  software
must set the designated slave select pin to the active level before
enabling the SERDES unit. To operate in SPI mode, once the transmit and receive bit counts
in  the  configuration  registers  are  programmed  with  non-zero
values,   the   SERDES   unit   begins   shifting   operations   on   the
programmed clock edges. Caution must be exercised to program
them quickly to avoid losing any data. USB 1.1 Protocol To set up a SERDES unit for USB mode, the received data output
of the USB transceiver should be connected to SxRXD. The VP
and VM pins of the transceiver are connected to the SxRXP and
SxRXM pins to allow detection of the EOP condition. Figure 4-11
shows   the   connections   required   between   an   external   USB
transceiver and the IP2022.