2006-2019 Microchip Technology Inc.
DS30009711C-page 9
I/O Ports with PPS
4.0
PERIPHERAL PIN SELECT
A major challenge in general purpose devices is providing the largest possible set of peripheral
features while minimizing the conflict of features on I/O pins. The challenge is even greater on
low pin count devices. In an application where more than one peripheral is needed to be
assigned to a single pin, inconvenient work arounds in application code or a complete redesign
may be the only option.
Peripheral Pin Select configuration provides an alternative to these choices by enabling users
peripheral set selection and their placement on a wide range of I/O pins. By increasing the pinout
options available on a particular device, users 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.
Users may 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.
4.1
Available Pins
The Peripheral Pin Select feature is used with a range of pins. The number of available pins is
dependent 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. If the pin supports only the input
function Peripheral Pin Select feature, then it will be designated as “RPIn”. For more details, refer
to the device pinout in the respective device data sheet.
4.2
Available Peripherals
The peripherals managed by the Peripheral Pin Select 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) and external interrupt inputs.
In comparison, some digital only peripheral modules are not currently included in the Peripheral
Pin Select feature. This is because the peripheral’s function requires special I/O circuitry on a
specific port and cannot be easily connected to multiple pins. These modules include I
2
C,
specialty communication (Ethernet and USB), Change Notification (CN) inputs, RTCC alarm
output and all modules with analog inputs, such as the A/D Converter.
A key difference between remappable and non-remappable peripherals is that 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
available on a default pin, assuming that the peripheral is active and not conflicting with another
peripheral.
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.
Note:
Some devices do not have this feature. Please refer to the specific device data
sheet for more details.