Datasheet

 2011-2012 Microchip Technology Inc. DS41441C-page 101
PIC12(L)F1840
12.0 I/O PORTS
In general, when a peripheral is enabled, that pin may
not be used as a general purpose I/O pin.
The port has three registers for its operation. These
registers are:
• TRISA register (data direction register)
• PORTA register (reads the levels on the pins of
the device)
• LATA register (output latch)
PORTA has the following additional registers. They
are:
• ANSELA (analog select)
• WPUA (weak pull-up)
The Data Latch (LATA register) is useful for
read-modify-write operations on the value that the I/O
pins are driving.
A write operation to the LATA register has the same
affect as a write to the corresponding PORTA register.
A read of the LATA register reads of the values held in
the I/O PORT latches, while a read of the PORTA
register reads the actual I/O pin value.
The port has analog functions and has an ANSELA.
register which can disable the digital input and save
power. A simplified model of a generic I/O port, without
the interfaces to other peripherals, is shown in
Figure 12-1.
FIGURE 12-1: GENERIC I/O PORT
OPERATION
12.1 Alternate Pin Function
The Alternate Pin Function Control (APFCON) register
is used to steer specific peripheral input and output
functions between different pins. The APFCON register
is shown in Register 12-1. For this device family, the
following functions can be moved between different
pins.
•RX/DT
•TX/CK
•SDO
•SS
(Slave Select)
•T1G
•P1B
• CCP1/P1A
These bits have no effect on the values of any TRIS
register. PORT and TRIS overrides will be routed to the
correct pin. The unselected pin will be unaffected.
QD
CK
Write LATx
Data Register
I/O pin
Read PORTx
Write PORTx
TRISx
Read LATx
Data Bus
To digital peripherals
ANSELx
VDD
VSS
To analog peripherals