IP2022 User’s Manual—Peripherals www.ubicom.com 293 COLLISION  is  connected  to  a  general-purpose  port  pin,  and
TxBUSY is connected to the SxTXME to provide additional flow
control capabilities for the software device driver. The COLLISION
signal  is  used  to  indicate  that  a  PHY  device  has  detected  a
collision condition. This signal is only useful when the SERDES is
connected to a PHY device or acting as a PHY device. The TxBUSY signal is used by a GPSI device to indicate that the
device  is  currently  busy,  and  that  another  device  should  not
attempt  to  start  a  data  transfer.  COLLISION  and  TxBUSY  are
asynchronous   to   both   TxClk   and   RxClk.   TxBUSY   can   be Table 4-9  GPSI Interface Signal Usage  GPSI
Signal Name SERDES Signal Name Direc- tion Description TxClk SxTXM I/O Transmit clock TxD SxTXP Output    Transmit data TxEn SxTXPE Output    Transmit data valid RxClk SxCLK I/O Receive clock RxD SxRXD Input Receive data RxEn SxRXP Input Receive data valid COLLSION    GPIO I/O Indicates a collision at PHY
layer (handled by software) TxBUSY SxTxME I/O Indicates a data transfer in
progress (handled by soft-
ware)