IP2022 User’s Manual—Similarities with SX-Series Devices www.ubicom.com 375 RTCC  External  Clock—The  RTCC  on  the  SX-Series  devices allowed an external clock source. The equivalent function on the
IP2022 does not have this option, however the real-timer timer can
accept an external clock for those applications which require this
functionality. I/O  Ports—The  SX-Series  devices  provided  options  for  on-chip pullup resistors, Schmitt trigger inputs, and TTL logic levels. The
IP2022 only allows CMOS logic levels and does not offer pullup or
Schmitt  trigger  options.  The  SX-Series  had  a  bit  for  specifying
whether a read from a port would read data sampled from the port
pins or the data register used to drive output port  pins. On the
IP2022,  both  of  these  options  are  always  available  by  reading
either the RxIN or RxOUT registers, respectively. All of the port
registers are mapped into the data memory of the IP2022, which
eliminates the need for the MODE register used on the SX-Series
devices.