Microchip Technology IC PIC MCU PIC16F1937-I/PT TQFP-44 MCP PIC16F1937-I/PT Data Sheet
Product codes
PIC16F1937-I/PT
PIC16(L)F1934/6/7
DS41364E-page 132
2008-2011 Microchip Technology Inc.
12.2
PORTA Registers
). Setting a TRISA bit (= 1) will make the
corresponding PORTA pin an input (i.e., disable the
output driver). Clearing a TRISA bit (= 0) will make the
corresponding PORTA pin an output (i.e., enables
output driver and puts the contents of the output latch
on the selected pin).
output driver). Clearing a TRISA bit (= 0) will make the
corresponding PORTA pin an output (i.e., enables
output driver and puts the contents of the output latch
on the selected pin).
shows how to
initialize an I/O port.
Reading the PORTA register (
Reading the PORTA register (
) reads the
status of the pins, whereas writing to it will write to the
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then
written to the PORT data latch (LATA).
The TRISA register (
PORT latch. All write operations are read-modify-write
operations. Therefore, a write to a port implies that the
port pins are read, this value is modified and then
written to the PORT data latch (LATA).
The TRISA register (
) controls the
PORTA pin output drivers, even when they are being
used as analog inputs. The user should ensure the bits
in the TRISA register are maintained set when using
them as analog inputs. I/O pins configured as analog
input always read ‘0’.
used as analog inputs. The user should ensure the bits
in the TRISA register are maintained set when using
them as analog inputs. I/O pins configured as analog
input always read ‘0’.
12.2.1
ANSELA REGISTER
The ANSELA register (
) is used to
configure the Input mode of an I/O pin to analog.
Setting the appropriate ANSELA bit high will cause all
digital reads on the pin to be read as ‘0’ and allow
analog functions on the pin to operate correctly.
The state of the ANSELA bits has no effect on digital
output functions. A pin with TRIS clear and ANSEL set
will still operate as a digital output, but the Input mode
will be analog. This can cause unexpected behavior
when executing read-modify-write instructions on the
affected port.
Setting the appropriate ANSELA bit high will cause all
digital reads on the pin to be read as ‘0’ and allow
analog functions on the pin to operate correctly.
The state of the ANSELA bits has no effect on digital
output functions. A pin with TRIS clear and ANSEL set
will still operate as a digital output, but the Input mode
will be analog. This can cause unexpected behavior
when executing read-modify-write instructions on the
affected port.
12.2.2
PORTA FUNCTIONS AND OUTPUT
PRIORITIES
PRIORITIES
Each PORTA pin is multiplexed with other functions. The
pins, their combined functions and their output priorities
are shown in
pins, their combined functions and their output priorities
are shown in
.
When multiple outputs are enabled, the actual pin
control goes to the peripheral with the highest priority.
Analog input functions, such as ADC, comparator and
CapSense inputs, are not shown in the priority lists.
These inputs are active when the I/O pin is set for
Analog mode using the ANSELx registers. Digital
output functions may control the pin when it is in Analog
mode with the priority shown in
control goes to the peripheral with the highest priority.
Analog input functions, such as ADC, comparator and
CapSense inputs, are not shown in the priority lists.
These inputs are active when the I/O pin is set for
Analog mode using the ANSELx registers. Digital
output functions may control the pin when it is in Analog
mode with the priority shown in
.
Note:
The ANSELA bits default to the Analog
mode after Reset. To use any pins as
digital general purpose or peripheral
inputs, the corresponding ANSEL bits
must be initialized to ‘0’ by user software.
mode after Reset. To use any pins as
digital general purpose or peripheral
inputs, the corresponding ANSEL bits
must be initialized to ‘0’ by user software.
TABLE 12-2:
PORTA OUTPUT PRIORITY
Pin Name
Function Priority
(1)
RA0
V
CAP
SEG12 (LCD)
SRNQ (SR Latch)
C2OUT (Comparator)
RA0
SRNQ (SR Latch)
C2OUT (Comparator)
RA0
RA1
SEG7 (LCD)
RA1
RA1
RA2
COM2 (LCD)
AN2 (DAC)
RA2
AN2 (DAC)
RA2
RA3
COM3 (LCD) 28-pin only
SEG15
RA3
SEG15
RA3
RA4
SEG4 (LCD)
SRQ (SR Latch)
C1OUT (Comparator)
CCP5, 28-pin only
RA4
SRQ (SR Latch)
C1OUT (Comparator)
CCP5, 28-pin only
RA4
RA5
V
CAP
(enabled by Config. Word)
SEG5 (LCD)
SRNQ (SR Latch)
C2OUT (Comparator)
RA5
SRNQ (SR Latch)
C2OUT (Comparator)
RA5
RA6
V
CAP
(enabled by Config. Word)
OSC2 (enabled by Config. Word)
CLKOUT (enabled by Config. Word)
SEG1 (LCD)
RA6
CLKOUT (enabled by Config. Word)
SEG1 (LCD)
RA6
RA7
OSC1/CLKIN (enabled by Config. Word)
SEG2 (LCD)
RA7
SEG2 (LCD)
RA7
Note 1:
Priority listed from highest to lowest.