Peripherals—IP2022 User’s Manual 232 www.ubicom.com pins are provided for those applications in which a separate power
supply is used for the I/O port pin output drivers. Port G has a
separate GVdd pin which can be used to run the Port G output
drivers at a voltage different from that used for the other ports,
however Port G must run from a 2.3–2.7V power supply. Each port has separate input, output, and configuration registers,
which  are  memory  mapped.  The  numbers  in  the  pin  names
correspond to the bit positions in these registers. These registers
allow  each  port  bit  to  be  individually  configured  as  a  general-
purpose  input  or  output  under  software  control.  Unused  pins
should be configured as outputs, to prevent them from floating.
Port  B  has  three  additional   registers  for   supporting   external
interrupts (see Section 4.1.1). In addition, each port pin has an alternate function used to support
the on-chip hardware peripherals, as listed in Table 4-1. Port A
and Port B support the multi-function timers Timer 1 and Timer 2.
Port B, Port C, and Port D support the Parallel Slave Peripheral
(PSP) and external memory functions. Port E and Port F support
the  serializer/deserializer  (SERDES)  units.  Port  G  supports  the
analog  to  digital  converter  (ADC)  and  the  analog  comparator.
Before enabling a hardware peripheral, configure the port pins for
input or output as required by the peripheral.