Datasheet

 2011 Microchip Technology Inc. Preliminary DS41576B-page 45
PIC12F752/HV752
5.0 I/O PORTS
For this device there is one port available, PORTA. 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.
PORTA has three standard registers for its operation.
These registers are:
• TRISA registers (data direction)
• PORTA registers (reads the levels on the pins of
the device)
• LATA registers (output latch)
Some ports may have one or more of the following
additional registers. These registers 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
effect as a write to the corresponding PORTA register.
A read of the LATA register reads the values held in the
I/O PORT latches, while a read of the PORTA register
reads the actual I/O pin value.
Ports that support analog inputs have an associated
ANSEL register. When an ANSELA 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 5-1.
FIGURE 5-1: GENERIC I/O PORTA
OPERATION
EXAMPLE 5-1: INITIALIZING PORTA
QD
CK
Write LATA
Data Register
I/O pin
Read PORTA
Write PORTA
TRISA
Read LATA
Data Bus
To peripherals
ANSELA
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