IC Microchip

PORTA is a 6-bit wide bi-directional port. The corresponding
data direction register is TRISA. Setting a
TRISA bit (=1) will make the corresponding PORTA pin
an input, i.e., put the corresponding output driver in a
hi-impedance mode. Clearing a TRISA bit (=0) will
make the corresponding PORTA pin an output, (i.e., put
the contents of the output latch on the selected pin).
The PORTA register reads the state of the pins,
whereas writing to it will write to the port latch. All write
operations are read-modify-write operations. Therefore,
a write to a port implies that the port pins are read,
this value is modified, and then written to the port data
latch.
Pin RA4 is multiplexed with the Timer0 module clock
input to become the RA4/T0CKI pin. The RA4/T0CKI
pin is a Schmitt Trigger input and an open drain output.
All other RA port pins have TTL input levels and full
CMOS output drivers.
Pin RA5 is multiplexed with the SSP to become the
RA5/SS pin.
On the PIC16C72A device, other PORTA pins are multiplexed
with analog inputs and analog VREF input. The
operation of each pin is selected by clearing/setting the
control bits in the ADCON1

IC Microchip

IC Microchip
Timer0: 8-bit timer/counter with 8-bit prescaler
Timer1: 16-bit timer/counter with prescaler,