Remappable Pins - Digilent Basys MX3 Reference Manual

Basys MX3™ Board Reference Manual
Refer to the PIC32MX3XX/4XX Family Datasheet, and the PIC32 Family Reference Manual, Section 12, IO Ports, for
more detailed information about the operation of the I/O Ports in the microcontroller.
1.4

Remappable Pins

Users may independently map the input and/or output of most digital peripherals to a fixed subset of digital I/O
pins. 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 port number.
The available peripherals to be mapped are digital-only. These include general serial communications (UART and
SPI), general purpose timer clock inputs, timer-related peripherals (input capture and output compare), and
interrupt-on-change inputs.
On the other hand, some peripheral modules cannot be included in the peripheral pin select feature because it
requires special I/O circuitry on a specific port and it cannot be easily connected to multiple pins. These modules
include I2C and analog-to-digital converters (ADC), among others.
Peripheral pin select features are controlled using two sets of Special Function Registers (SFRs): one to map
peripheral inputs, and one to map peripheral outputs.
The peripheral inputs are mapped and named from the peripheral perspective (based on the peripheral). The [pin
name]R registers, where [pin name] refers to the specific peripheral pins, are used to configure peripheral input
mapping. TABLE 12-1 in the PIC32MX370F512L datasheet from Microchip (and Appendix 1 in this document)
shows the different pins and their values available to assign to a peripheral pin.
The following example shows how different I/Os, such as pin RF4, can be assigned to U1RX input pin of the UART1
peripheral:
U1RXR = 0x02; // 0010 corresponds to RF4
The peripheral outputs are mapped and named from the pin perspective (on the basis of the pin). The RPnR
registers (Register 12-2) are used to control output mapping. The PIC32MX370F512L datasheet details in TABLE 12-
2 (and Appendix 2 in this document) the values corresponding to each IO pin, associated to each available
peripheral pin. Note that the current version of the Basys MX3 schematic (B.0) incorrectly lists RD6 and RD7 as
remappable pins (RPD6 and RPD7, respectively); these pins are not remappable on the PIC32MX370F512L.
The following example shows how different peripheral outputs, such as U3TX, can be assigned to pin RF4:
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Figure 1.3. Remappable input example.
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