Datasheet

 2011 Microchip Technology Inc. DS41391D-page 117
PIC16(L)F1826/27
12.0 I/O PORTS
Depending on the device selected and peripherals
enabled, there are two ports available. In general,
when a peripheral is enabled, that pin may not be used
as a general purpose I/O pin.
Each port has three registers for its operation. These
registers are:
• TRISx registers (data direction register)
• PORTx registers (reads the levels on the pins of
the device)
• LATx registers (output latch)
Some ports may have one or more of the following
additional registers. These registers are:
• ANSELx (analog select)
• WPUx (weak pull-up)
The Data Latch (LATx registers) is useful for
read-modify-write operations on the value that the I/O
pins are driving.
A write operation to the LATx register has the same
effect as a write to the corresponding PORTx register.
A read of the LATx register reads of the values held in
the I/O PORT latches, while a read of the PORTx
register reads the actual I/O pin value.
Ports with analog functions also have an ANSELx
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
EXAMPLE 12-1: INITIALIZING PORTA
TABLE 12-1: PORT AVAILABILITY PER
DEVICE
Device
PORTA
PORTB
PORTC
PIC16(L)F1826 ●●
PIC16(L)F1827 ●●●
QD
CK
Write LATx
Data Register
I/O pin
Read PORTx
Write PORTx
TRISx
Read LATx
Data Bus
To peripherals
ANSELx
VDD
VSS
; This code example illustrates
; initializing the PORTA register. The
; other ports are initialized in the same
; manner.
BANKSEL PORTA ;
CLRF PORTA ;Init PORTA
BANKSEL LATA ;Data Latch
CLRF LATA ;
BANKSEL ANSELA ;
CLRF ANSELA ;digital I/O
BANKSEL TRISA ;
MOVLW B'00111000' ;Set RA<5:3> as inputs
MOVWF TRISA ;and set RA<2:0> as
;outputs