DSPIC33FJ12MC02ESS datasheet(107/284 Pages) MICROCHIP

107 / 284 page

Preliminary

DS70265B-page 105

dsPIC33FJ12MC201/202

9.0

I/O PORTS

All of the device pins (except VDD, VSS, 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.

9.1

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

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 9-1 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

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

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.

FIGURE 9-1:

BLOCK DIAGRAM OF A TYPICAL SHARED PORT STRUCTURE

Note:

This data sheet summarizes the features

of the dsPIC33FJ12MC201/202 devices.

It is not intended to be a comprehensive

reference source. To complement the

information in this data sheet, refer to the

“dsPIC33F Family Reference Manual”.

Please see the Microchip web site

(www.microchip.com)

for

the

latest

dsPIC33F Family Reference Manual

chapters.

WR LAT +

TRIS Latch

I/O Pin

WR Port

Data Bus

Data Latch

Read Port

Read TRIS

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

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