Datasheet

 2011 Microchip Technology Inc. Preliminary DS41585A-page 75
PIC10(L)F320/322
10.0 I/O PORT
Depending on which peripherals are enabled, some or
all of the pins may not be available as general purpose
I/O. 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 register (data direction)
• PORTA register (reads the levels on the pins of
the device)
• LATA register (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 of 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
ANSELA 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 10-1.
FIGURE 10-1: I/O PORT OPERATION
EXAMPLE 10-1: 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 ;not required on devices with 1 Bank of SFRs
CLRF PORTA ;Init PORTA
BANKSEL LATA ;not required on devices with 1 Bank of SFRs
CLRF LATA ;
BANKSEL ANSELA ;not required on devices with 1 Bank of SFRs
CLRF ANSELA ;digital I/O
BANKSEL TRISA ;not required on devices with 1 Bank of SFRs
MOVLW B'00000011' ;Set RA<1:0> as inputs
MOVWF TRISA ;and set RA<2:3> as
;outputs