Microchip Technology MA330017 Data Sheet
© 2007-2012 Microchip Technology Inc.
DS70283K-page 117
dsPIC33FJ32MC202/204 and dsPIC33FJ16MC304
10.0 I/O PORTS
All of the device pins (except V
DD
, V
SS
, MCLR and
OSC1/CLKI) are shared among the peripherals and the
parallel I/O ports. All I/O input ports feature Schmitt
Trigger inputs for improved noise immunity.
parallel I/O ports. All I/O input ports feature Schmitt
Trigger inputs for improved noise immunity.
10.1
Parallel I/O (PIO) Ports
Generally a parallel I/O port that shares a pin with a
peripheral is subservient to the peripheral. The
peripheral’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
peripheral is subservient to the peripheral. The
peripheral’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.
which a port’s digital output can drive the input of a
peripheral that shares the same pin.
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
can be read, but the output driver for the parallel port bit
is disabled. If a peripheral is enabled, but the peripheral
is not actively driving a pin, that pin can be driven by a
port.
All port pins have three registers directly associated
with their operation as digital I/O. 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
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
can be read, but the output driver for the parallel port bit
is disabled. If a peripheral is enabled, but the peripheral
is not actively driving a pin, that pin can be driven by a
port.
All port pins have three registers directly associated
with their operation as digital I/O. 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 latch (LATx) read the latch.
Writes to the latch write the latch. Reads from the port
(PORTx) read the port pins, while 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
function that is defined as an input only, it is
nevertheless regarded as a dedicated port because
there is no other competing source of outputs.
Reset. Reads from the latch (LATx) read the latch.
Writes to the latch write the latch. Reads from the port
(PORTx) read the port pins, while 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
function that is defined as an input only, it is
nevertheless regarded as a dedicated port because
there is no other competing source of outputs.
FIGURE 10-1:
BLOCK DIAGRAM OF A TYPICAL SHARED PORT STRUCTURE
Note 1: This data sheet summarizes the features
of the dsPIC33FJ32MC202/204 and
dsPIC33FJ16MC304 devices. It is not
intended to be a comprehensive refer-
ence source. To complement the infor-
mation in this data sheet, refer to Section
10. “I/O Ports” (DS70193) of the
“dsPIC33F/PIC24H Family Reference
Manual”, which is available on Microchip
web site (
dsPIC33FJ16MC304 devices. It is not
intended to be a comprehensive refer-
ence source. To complement the infor-
mation in this data sheet, refer to Section
10. “I/O Ports” (DS70193) of the
“dsPIC33F/PIC24H Family Reference
Manual”, which is available on Microchip
web site (
www.microchip.com
).
2: Some registers and associated bits
described in this section may not be
available on all devices. Refer to
available on all devices. Refer to
in
this data sheet for device-specific register
and bit information.
and bit information.
Q
D
CK
WR LAT +
TRIS Latch
I/O Pin
WR Port
Data Bus
Q
D
CK
Data Latch
Read Port
Read TRIS
1
0
1
0
WR TRIS
Peripheral Output Data
Output Enable
Peripheral Input Data
I/O
Peripheral Module
Peripheral Output Enable
PIO Module
Output Multiplexers
Output Data
Input Data
Peripheral Module Enable
Read LAT