Microchip Technology MA160014 データシート
2010-2012 Microchip Technology Inc.
DS41412F-page 151
PIC18(L)F2X/4XK22
10.6
PORTE Registers
Depending on the particular PIC18(L)F2X/4XK22
device selected, PORTE is implemented in two
different ways.
device selected, PORTE is implemented in two
different ways.
10.6.1
PORTE ON 40/44-PIN DEVICES
For PIC18(L)F2X/4XK22 devices, PORTE is a 4-bit
wide port. Three pins (RE0/P3A/CCP3/AN5, RE1/P3B/
AN6 and RE2/CCP5/AN7) are individually configurable
as inputs or outputs. These pins have Schmitt Trigger
input buffers. When selected as an analog input, these
pins will read as ‘0’s.
wide port. Three pins (RE0/P3A/CCP3/AN5, RE1/P3B/
AN6 and RE2/CCP5/AN7) are individually configurable
as inputs or outputs. These pins have Schmitt Trigger
input buffers. When selected as an analog input, these
pins will read as ‘0’s.
The corresponding data direction register is TRISE.
Setting a TRISE bit (= 1) will make the corresponding
PORTE pin an input (i.e., disable the output driver).
Clearing a TRISE bit (= 0) will make the corresponding
PORTE pin an output (i.e., enable the output driver and
put the contents of the output latch on the selected pin).
Setting a TRISE bit (= 1) will make the corresponding
PORTE pin an input (i.e., disable the output driver).
Clearing a TRISE bit (= 0) will make the corresponding
PORTE pin an output (i.e., enable the output driver and
put the contents of the output latch on the selected pin).
TRISE controls the direction of the REx pins, even
when they are being used as analog inputs. The user
must make sure to keep the pins configured as inputs
when using them as analog inputs.
when they are being used as analog inputs. The user
must make sure to keep the pins configured as inputs
when using them as analog inputs.
The Data Latch register (LATE) is also memory
mapped. Read-modify-write operations on the LATE
register read and write the latched output value for
PORTE.
mapped. Read-modify-write operations on the LATE
register read and write the latched output value for
PORTE.
The fourth pin of PORTE (MCLR/V
PP
/RE3) is an input
only pin. Its operation is controlled by the MCLRE
Configuration bit. When selected as a port pin
(MCLRE = 0), it functions as a digital input only pin; as
such, it does not have TRIS or LAT bits associated with its
operation. Otherwise, it functions as the device’s Master
Clear input. In either configuration, RE3 also functions as
the programming voltage input during programming.
Configuration bit. When selected as a port pin
(MCLRE = 0), it functions as a digital input only pin; as
such, it does not have TRIS or LAT bits associated with its
operation. Otherwise, it functions as the device’s Master
Clear input. In either configuration, RE3 also functions as
the programming voltage input during programming.
EXAMPLE 10-5:
INITIALIZING PORTE
10.6.2
PORTE ON 28-PIN DEVICES
For PIC18F2XK22 devices, PORTE is only available
when Master Clear functionality is disabled
(MCLR = 0). In these cases, PORTE is a single bit,
input only port comprised of RE3 only. The pin operates
as previously described.
when Master Clear functionality is disabled
(MCLR = 0). In these cases, PORTE is a single bit,
input only port comprised of RE3 only. The pin operates
as previously described.
10.6.3
RE3 WEAK PULL-UP
The port RE3 pin has an individually controlled weak
internal pull-up. When set, the WPUE3 (TRISE<7>) bit
enables the RE3 pin pull-up. The RBPU bit of the
INTCON2 register controls pull-ups on both PORTB
and PORTE. When RBPU = 0, the weak pull-ups
become active on all pins which have the WPUE3 or
WPUBx bits set.
internal pull-up. When set, the WPUE3 (TRISE<7>) bit
enables the RE3 pin pull-up. The RBPU bit of the
INTCON2 register controls pull-ups on both PORTB
and PORTE. When RBPU = 0, the weak pull-ups
become active on all pins which have the WPUE3 or
WPUBx bits set.
When set, the RBPU bit disables all
weak pull-ups. The pull-ups are disabled on a Power-
on Reset. When the RE3 port pin is configured as
MCLR, (CONFIG3H<7>, MCLRE=1 and
CONFIG4L<2>, LVP=0), or configured for Low Voltage
Programming, (MCLRE=x and LVP=1), the pull-up is
always enabled and the WPUE3 bit has no effect.
on Reset. When the RE3 port pin is configured as
MCLR, (CONFIG3H<7>, MCLRE=1 and
CONFIG4L<2>, LVP=0), or configured for Low Voltage
Programming, (MCLRE=x and LVP=1), the pull-up is
always enabled and the WPUE3 bit has no effect.
10.6.4
PORTE OUTPUT PRIORITY
Each PORTE pin is multiplexed with other functions.
The pins, their combined functions and their output
priorities are briefly described here. For additional
information, refer to the appropriate section in this data
sheet.
The pins, their combined functions and their output
priorities are briefly described here. For additional
information, refer to the appropriate section in this data
sheet.
When multiple outputs are enabled, the actual pin
control goes to the peripheral with the higher priority.
control goes to the peripheral with the higher priority.
lists the PORTE pin functions from the
highest to the lowest priority.
Analog input functions, such as ADC, comparator and
SR latch inputs, are not shown in the priority lists.
SR latch 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 below.
Analog mode using the ANSELx registers. Digital
output functions may control the pin when it is in Analog
mode with the priority shown below.
Note:
On a Power-on Reset, RE<2:0> are
configured as analog inputs.
configured as analog inputs.
Note:
On a Power-on Reset, RE3 is enabled as
a digital input only if Master Clear
functionality is disabled.
a digital input only if Master Clear
functionality is disabled.
CLRF
PORTE
; Initialize PORTE by
; clearing output
; data latches
CLRF
LATE
; Alternate method
; to clear output
; data latches
CLRF
ANSELE
; Configure analog pins
; for digital only
MOVLW
05h
; Value used to
; initialize data
; direction
MOVWF
TRISE
; Set RE<0> as input
; RE<1> as output
; RE<2> as input