Microchip Technology AC244045 Data Sheet
2010-2012 Microchip Technology Inc.
DS41440C-page 119
PIC16(L)F1825/1829
12.0 I/O PORTS
Depending on the device selected and peripherals
enabled, there are up to two ports available. In general,
when a peripheral is enabled on a port pin, that pin
cannot be used as a general purpose output. However,
the pin can still be read.
Each port has three standard registers for its operation.
These registers are:
• TRISx registers (data direction)
• PORTx registers (reads the levels on the pins of
enabled, there are up to two ports available. In general,
when a peripheral is enabled on a port pin, that pin
cannot be used as a general purpose output. However,
the pin can still be read.
Each port has three standard registers for its operation.
These registers are:
• TRISx registers (data direction)
• 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)
• INLVLx (input level control)
Some ports may have one or more of the following
additional registers. These registers are:
• ANSELx (analog select)
• WPUx (weak pull-up)
• INLVLx (input level control)
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 that support analog inputs have an associated
ANSELx register. When an ANSEL bit is set, the digital
input buffer associated with that bit is disabled.
Disabling the input buffer prevents analog signal levels
on the pin between a logic high and low from causing
excessive current in the logic input circuitry. A
simplified model of a generic I/O port, without the
interfaces to other peripherals, is shown in
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 that support analog inputs have an associated
ANSELx register. When an ANSEL bit is set, the digital
input buffer associated with that bit is disabled.
Disabling the input buffer prevents analog signal levels
on the pin between a logic high and low from causing
excessive current in the logic input circuitry. A
simplified model of a generic I/O port, without the
interfaces to other peripherals, is shown in
FIGURE 12-1:
GENERIC I/O PORT
OPERATION
OPERATION
EXAMPLE 12-1:
INITIALIZING PORTA
TABLE 12-1:
PORT AVAILABILITY PER
DEVICE
DEVICE
Device
PORT
A
PO
RTB
PORTC
PIC16(L)F1825
●
●
PIC16(L)F1829
●
●
●
Q
D
CK
Write LATx
Data Register
I/O pin
Read PORTx
Write PORTx
TRISx
Read LATx
Data Bus
To peripherals
ANSELx
V
DD
V
SS
; This code example illustrates
; initializing the PORTA register. The
; other ports are initialized in the same
; manner.
; 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
;outputs