DSPIC33FJ12MC02ESS datasheet(109/284 Pages) MICROCHIP

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Preliminary

DS70265B-page 107

dsPIC33FJ12MC201/202

9.4

Peripheral Pin Select

Peripheral pin select configuration enables peripheral

set selection and placement on a wide range of I/O

pins. By increasing the pinout options available on a

particular device, programmers can better tailor the

microcontroller to their entire application, rather than

trimming the application to fit the device.

The peripheral pin select configuration feature

operates over a fixed subset of digital I/O pins.

Programmers can independently map the input and/or

output of most digital peripherals to any one of these I/

O pins. Peripheral pin select is performed in software,

and generally does not require the device to be

reprogrammed. Hardware safeguards are included

that prevent accidental or spurious changes to the

peripheral mapping, once it has been established.

9.4.1

AVAILABLE PINS

The peripheral pin select feature is used with a range

of up to 16 pins. The number of available pins depends

on the particular device and its pin count. Pins that

support the peripheral pin select feature include the

designation “RPn” in their full pin designation, where

“RP” designates a remappable peripheral and “n” is the

remappable pin number.

9.4.2

AVAILABLE PERIPHERALS

The peripherals managed by the peripheral pin select

feature are all digital-only peripherals. These include:

• General serial communications (UART and SPI)

• General purpose timer clock inputs

• Timer-related peripherals (input capture and

output compare)

• Interrupt-on-change inputs

In comparison, some digital-only peripheral modules

are never included in the peripheral pin select feature.

This is because the peripheral’s function requires spe-

cial I/O circuitry on a specific port and cannot be easily

connected to multiple pins. These modules include I2C.

A similar requirement excludes all modules with analog

inputs, such as the Analog-to-Digital Converter (ADC).

Remappable peripherals are not associated with a

default I/O pin. The peripheral must always be

assigned to a specific I/O pin before it can be used. In

contrast, non remappable peripherals are always avail-

able on a default pin, assuming that the peripheral is

active and not conflicting with another peripheral.

9.4.2.1

Peripheral Pin Select Function

Priority

When a remappable peripheral is active on a given I/O

pin, it takes priority over all other digital I/O and digital

communication peripherals associated with the pin.

Priority is given regardless of the type of peripheral that

is mapped. Remappable peripherals never take priority

over any analog functions associated with the pin.

9.4.3

CONTROLLING PERIPHERAL PIN

SELECT

Peripheral pin select features are controlled through

two sets of special function registers: one to map

peripheral inputs, and one to map outputs. Because

they are separately controlled, a particular peripheral’s

input and output (if the peripheral has both) can be

placed on any selectable function pin without

constraint.

The association of a peripheral to a peripheral select-

able pin is handled in two different ways, depending on

whether an input or output is being mapped.

9.4.3.1

Input Mapping

The inputs of the peripheral pin select options are

mapped on the basis of the peripheral. A control

will be mapped to. The RPINRx registers are used to

configure peripheral input mapping (see Register 9-1

through Register 9-13). Each register contains sets of

5-bit fields, with each set associated with one of the

remappable

peripherals.

Programming

given

peripheral’s bit field with an appropriate 5-bit value

maps the RPn pin with that value to that peripheral.

For any given device, the valid range of values for any

bit field corresponds to the maximum number of

peripheral pin selections supported by the device.

Figure 9-2 Illustrates remappable pin selection for

U1RX input.

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