PIC24FJ256DA210 Datasheet, PDF (157/408 Pages) Microchip Technology – 64/100-Pin, 16-Bit Flash Microcontrollers with Graphics Controller and USB On-The-Go (OTG)

PIC24FJ256DA210 FAMILY
10.0 I/O PORTS
Note:
This data sheet summarizes the features
of this group of PIC24F devices. It is not
intended to be a comprehensive reference
source. For more information, refer to the
“PIC24F Family Reference Manual”,
Section 12. “I/O Ports with Peripheral
Pin Select (PPS)” (DS39711). The infor-
mation in this data sheet supersedes the
information in the FRM.
All of the device pins (except VDD, VSS, MCLR and
OSCI/CLKI) are shared between the peripherals and
the parallel I/O ports. All I/O input ports feature Schmitt
Trigger (ST) inputs for improved noise immunity.
10.1 Parallel I/O (PIO) Ports
A parallel I/O port that shares a pin with a peripheral is,
in general, subservient to the peripheral. The periph-
eral’s output buffer data and control signals are
provided to a pair of multiplexers. The multiplexers
select whether the peripheral or the associated port
has ownership 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 10-1 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 the peripheral is
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.
All port pins have three registers directly associated
with their operation as digital I/O and one register asso-
ciated with their operation as analog input. The Data
Direction register (TRISx) determines whether the pin
is an input or an output. If the data direction bit is a ‘1’,
then the pin is an input. All port pins are defined as
inputs after a Reset. Reads from the Output Latch reg-
ister (LATx), read the latch; writes to the latch, write the
latch. Reads from the port (PORTx), read the port pins;
writes to the port pins, write the latch.
Any bit and its associated data and control registers
that are not valid for a particular device will be
disabled. That means the corresponding LATx and
TRISx registers, and the port pin will read as zeros.
When a pin is shared with another peripheral or func-
tion that is defined as an input only, it is regarded as a
dedicated port because there is no other competing
source of inputs.
FIGURE 10-1:
BLOCK DIAGRAM OF A TYPICAL SHARED PORT STRUCTURE
Peripheral Module
Peripheral Input Data
Peripheral Module Enable
Peripheral Output Enable
Peripheral Output Data
Output Multiplexers
I/O
1 _{Output Enable}
0
Read TRIS
PIO Module
1 _{Output Data}
0
Data Bus
WR TRIS
WR LAT +
WR PORT
Read LAT
Read PORT
D
Q
CK
TRIS Latch
D
Q
CK
Data Latch
I/O Pin
Input Data
 2010 Microchip Technology Inc.
DS39969B-page 157