pic32mx320f064h Microchip Technology Inc., pic32mx320f064h Datasheet - Page 263

• Manufacturer Part Number: pic32mx320f064h
• Description: 64/100-pin General Purpose, 32-bit Flash Microcontrollers
• Manufacturer: Microchip Technology Inc.

12.2.6
In addition to the PORT, LAT and TRIS registers for
data control, each port pin configured as a digital output
can also select between an active drive output and
open-drain output. This is controlled by the Open-Drain
Control register, ODCx, associated with each port.
From POR, when an IO pin is configured as a digital
output, its output is active drive by default. Setting a bit
in the ODCx register = 1 configures the corresponding
pin as an open-drain output.
The open-drain feature allows the generation of
outputs higher than V
digital-only pins by using external pull-up resistors. The
maximum open-drain voltage allowed is the same as
the maximum V
12.2.7
in general, subservient to the peripheral. The periph-
eral’s output buffer data and control signals are pro-
vided to a pair of multiplexers. The multiplexers select
whether the peripheral or the associated port has own-
ership of the output data and control signals of the I/O
pin. The logic also prevents “loop through”, in which a
port’s digital output can drive the input of a peripheral
that shares the same pin. Figure 12-2 shows how ports
are shared with other peripherals and the associated
I/O pin to which they are connected.
When a peripheral is enabled and actively driving an
associated pin, the use of the pin as a general purpose
output pin is disabled. The I/O pin may be read, but the
output driver for the parallel port bit will be disabled. If
a peripheral is enabled, but the peripheral is not
actively driving a pin, that pin may be driven by a port.
12.2.8
Some peripheral inputs assigned to an I/O pin may not
take control of the I/O pin output driver. If the I/O pin
associated with the peripheral is configured as an out-
put, using the appropriate TRIS control bit, the user can
manually affect the state of the peripheral’s input pin
through its corresponding LAT register. This behavior
can be useful in some situations, especially for testing
purposes, when no external signal is connected to the
input pin.
In general, the following peripherals allow their input
pins to be controlled manually through the LAT
registers:
• External Interrupt pins
• Timer Clock Input pins
• Input Capture pins
• PWM Fault pins
© 2007 Microchip Technology Inc.
A parallel I/O port that shares a pin with a peripheral is,
OPEN-DRAIN CONFIGURATION
PERIPHERAL MULTIPLEXING
SOFTWARE INPUT PIN CONTROL
IH
specification, typically 5.5v.
DD
, e.g., 5V, on any desired
Advance Information
Most serial communication peripherals, when enabled,
take full control of the I/O pin so that the input pins
associated with the peripheral cannot be affected
through the corresponding PORT registers. These
peripherals include the following modules:
• SPI
• I
• UART
12.2.9
Certain PIC32MX I/O port pins provide Input Change
notification that can generate interrupt requests to the
processor in response to a Change-Of-State (COS) on
those selected input pins. The initial state of any
enabled Change Notice (CN) pin must be established
by reading the corresponding PORT register. This fea-
ture is capable of detecting input COS even in Sleep
mode, when the clocks are disabled. Depending on the
device pin count, there are up to 22 external signals
(CN0 through CN21) that may be selected (enabled)
for generating an interrupt request on a COS.
The following control registers are associated with the
change notice module:
• CNCON
• CNEN
• CNPUE
The CNCON control register ON bit enables or disables
the CN module and its ability to generate interrupts or
respond to mismatch conditions.
The CNEN (change notice enable) register control bits
enable each CN input. Setting any of these bits enables
a CN for the corresponding pins.
The CNPUE (change notice pull-up enable) register
control bits enable a weak pull-up to a corresponding
CN input pin. The pull-ups act as a current source that
is connected to the pin, and eliminate the need for
external resistors when push button or keypad devices
are connected.
Note:
2
C™
PIC32MX FAMILY
INPUT CHANGE NOTIFICATION
Pull-up resistors on change notification
pins should always be disabled whenever
the port pin is configured as a digital
output.
DS61143A - page 261