PIC24HJ16GP304-E Datasheet, PDF (105/274 Pages) Microchip Technology – High-Performance, 16-bit Microcontrollers

PIC24HJ32GP202/204 AND PIC24HJ16GP304
10.6 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 must be assigned to a single pin, inconve-
nient workarounds in application code or a complete
redesign may be the only option.
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.
10.6.1 AVAILABLE PINS
The peripheral pin select feature is used with a range
of up to 26 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.
10.6.2 CONTROLLING PERIPHERAL PIN
SELECT
Peripheral pin select features are controlled through
two sets of special function registers to map
peripherals and to map outputs.
Since 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 output is being
mapped.
10.6.2.1 Input Mapping
The inputs of the peripheral pin select options are
mapped on the basis of the peripheral. A control
register associated with a peripheral dictates the pin it
will be mapped to. The RPINRx registers are used to
configure peripheral input mapping (see Register 10-1
through Register 10-9). Each register contains sets of
5-bit fields, with each set associated with one of the
remappable peripherals. Programming a 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 10-2 Illustrates remappable pin selection for
U1RX input.
Note:
For input mapping only, the Peripheral Pin
Select (PPS) functionality does not have
priority over the TRISx settings. There-
fore, when configuring the RPn pin for
input, the corresponding bit in the TRISx
register must also be configured for input
(i.e., set to ‘1’).
FIGURE 10-2:
REMAPPABLE MUX
INPUT FOR U1RX
U1RXR<4:0>
0
RP0
1
RP1
U1RX input
to peripheral
2
RP2
25
RP25
© 2007-2011 Microchip Technology Inc.
DS70289H-page 105