PIC18F45J10 Datasheet, PDF (95/358 Pages) Microchip Technology – 28/40/44-Pin High-Performance RISC Microcontrollers with nanoWatt Technology

PIC18F45J10 FAMILY
9.0 I/O PORTS
Depending on the device selected and features
enabled, there are up to five ports available. Some pins
of the I/O ports are multiplexed with an alternate
function from the peripheral features on the device. In
general, when a peripheral is enabled, that pin may not
be used as a general purpose I/O pin.
Each port has three registers for its operation. These
registers are:
• TRIS register (data direction register)
• Port register (reads the levels on the pins of the
device)
• LAT register (output latch)
The Data Latch (LAT register) is useful for read-modify-
write operations on the value that the I/O pins are
driving.
A simplified model of a generic I/O port, without the
interfaces to other peripherals, is shown in Figure 9-1.
FIGURE 9-1:
GENERIC I/O PORT
OPERATION
RD LAT
Data
Bus
WR LAT
or Port
WR TRIS
RD TRIS
RD Port
D
Q
CK
Data Latch
DQ
CK
TRIS Latch
Q
D
ENEN
I/O pin⁽¹⁾
Input
Buffer
Note 1: I/O pins have diode protection to VDD and VSS.
9.1 I/O Port Pin Capabilities
When developing an application, the capabilities of the
port pins must be considered. Outputs on some pins
have higher output drive strength than others. Similarly,
some pins can tolerate higher than VDD input levels.
9.1.1 PIN OUTPUT DRIVE
The output pin drive strengths vary for groups of pins
intended to meet the needs for a variety of applications.
PORTB and PORTC are designed to drive higher
loads, such as LEDs. All other ports are designed for
small loads, typically indication only. Table 9-1 sum-
marizes the output capabilities. Refer to Section 23.0
“Electrical Characteristics” for more details.
TABLE 9-1: OUTPUT DRIVE LEVELS
Port
Drive
Description
PORTA
PORTD
PORTE
PORTB
PORTC
Minimum Intended for indication.
High
Suitable for direct LED drive
levels.
9.1.2
INPUT PINS AND VOLTAGE
CONSIDERATIONS
The voltage tolerance of pins used as device inputs is
dependent on the pin’s input function. Pins that are used
as digital only inputs are able to handle DC voltages up
to 5.5V; a level typical for digital logic circuits. In contrast,
pins that also have analog input functions of any kind
can only tolerate voltages up to VDD. Voltage excursions
beyond VDD on these pins should be avoided. Table 9-2
summarizes the input capabilities. Refer to
Section 23.0 “Electrical Characteristics” for more
details.
TABLE 9-2:
Port or Pin
PORTA<5:0>
PORTB<5:0>
PORTC<1:0>
PORTE<2:0>
PORTB<7:6>
PORTC<7:2>
PORTD<7:0>
INPUT VOLTAGE LEVELS
Tolerated
Input
Description
VDD
Only VDD input levels
tolerated.
5.5V
Tolerates input levels
above VDD, useful for
most standard logic.
© 2007 Microchip Technology Inc.
Preliminary
DS39682C-page 93