PIC18F44J50-I Datasheet, PDF (150/562 Pages) Microchip Technology – 28/44-Pin, Low-Power, High-Performance USB Microcontrollers

PIC18F46J50 FAMILY
10.7 Peripheral Pin Select (PPS)
A major challenge in general purpose devices is provid-
ing 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
similar to the PIC18F46J50 family. In an application
that needs to use more than one peripheral multiplexed
on a single pin, inconvenient work arounds in applica-
tion code, or a complete redesign, may be the only
option.
The Peripheral Pin Select (PPS) feature provides an
alternative to these choices by enabling the user’s
peripheral set selections 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 PPS feature operates over a fixed subset of digital
I/O pins. Users may independently map the input and/
or output of any one of the many digital peripherals to
any one of these I/O pins. PPS 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.
10.7.1 AVAILABLE PINS
The PPS feature is used with a range of up to 22 pins.
The number of available pins is dependent on the
particular device and its pin count. Pins that support the
PPS feature include the designation “RPn” in their full
pin designation, where “RP” designates a remappable
peripheral and “n” is the remappable pin number. See
Table 1-2 for pinout options in each package offering.
10.7.2 AVAILABLE PERIPHERALS
The peripherals managed by the PPS are all digital
only peripherals. These include general serial commu-
nications (UART and SPI), general purpose timer clock
inputs, timer-related peripherals (input capture and
output compare) and external interrupt inputs. Also
included are the outputs of the comparator module,
since these are discrete digital signals.
The PPS module is not applied to I²C, change notifica-
tion inputs, RTCC alarm outputs or peripherals with
analog inputs. Additionally, the MSSP1 and EUSART1
modules are not routed through the PPS module.
A key difference between pin select and non-pin select
peripherals is that pin select peripherals are not asso-
ciated 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-pin select peripherals are always
available on a default pin, assuming that the peripheral
is active and not conflicting with another peripheral.
10.7.2.1 Peripheral Pin Select Function
Priority
When a pin-selectable 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. Pin select peripherals never take priority
over any analog functions associated with the pin.
10.7.3
CONTROLLING PERIPHERAL PIN
SELECT
PPS features are controlled through two sets of Special
Function Registers (SFRs): one to map peripheral
inputs and the other 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-
selectable pin is handled in two different ways,
depending on whether an input or an output is being
mapped.
DS39931D-page 150
 2011 Microchip Technology Inc.