Datasheet

© 2011-2014 Microchip Technology Inc. DS60001168F-page 147
PIC32MX1XX/2XX
11.3.5 OUTPUT MAPPING
In contrast to inputs, the outputs of the PPS options
are mapped on the basis of the pin. In this case, a
control register associated with a particular pin
dictates the peripheral output to be mapped. The
RPnR registers (Register 11-2) are used to control
output mapping. Like the [pin name]R registers, each
register contains sets of 4 bit fields. The value of the
bit field corresponds to one of the peripherals, and
that peripheral’s output is mapped to the pin (see
Table 11-2 and Figure 11-3).
A null output is associated with the output register reset
value of ‘0’. This is done to ensure that remappable
outputs remain disconnected from all output pins by
default.
FIGURE 11-3: EXAMPLE OF
MULTIPLEXING OF
REMAPPABLE OUTPUT
FOR RPA0
11.3.6 CONTROLLING CONFIGURATION
CHANGES
Because peripheral remapping can be changed during
run time, some restrictions on peripheral remapping
are needed to prevent accidental configuration
changes. PIC32 devices include two features to
prevent alterations to the peripheral map:
• Control register lock sequence
• Configuration bit select lock
11.3.6.1 Control Register Lock Sequence
Under normal operation, writes to the RPnR and [pin
name]R registers are not allowed. Attempted writes
appear to execute normally, but the contents of the
registers remain unchanged. To change these regis-
ters, they must be unlocked in hardware. The regis-
ter lock is controlled by the Configuration bit,
IOLOCK (CFGCON<13>). Setting IOLOCK prevents
writes to the control registers; clearing IOLOCK
allows writes.
To set or clear the IOLOCK bit, an unlock sequence
must be executed. Refer to Section 6. “Oscillator”
(DS60001112) in the “PIC32 Family Reference
Manual” for details.
11.3.6.2 Configuration Bit Select Lock
As an additional level of safety, the device can be
configured to prevent more than one write session to
the RPnR and [pin name]R registers. The Configuration
bit, IOL1WAY (DEVCFG3<29>), blocks the IOLOCK bit
from being cleared after it has been set once. If
IOLOCK remains set, the register unlock procedure
does not execute, and the PPS control registers cannot
be written to. The only way to clear the bit and re-
enable peripheral remapping is to perform a device
Reset.
In the default (unprogrammed) state, IOL1WAY is set,
restricting users to one write session.
RPA0R<3:0>
0
15
1
Default
U1TX Output
U1RTS Output
2
14
Output Data
RPA0