PIC18F27J53T-I/SO Microchip Technology, PIC18F27J53T-I/SO Datasheet - Page 163

• Manufacturer Part Number: PIC18F27J53T-I/SO
• Description: 28-pin, USB, 128KB Flash, 4KB RAM, 12 MIPS, 12-bit ADC, NanoWatt XLP 28 SOIC .30
• Manufacturer: Microchip Technology
• Series: PIC® XLP™ 18Fr

Specifications of PIC18F27J53T-I/SO

• Core Processor: PIC
• Core Size: 8-Bit
• Speed: 48MHz
• Connectivity: I²C, LIN, SPI, UART/USART, USB
• Peripherals: Brown-out Detect/Reset, POR, PWM, WDT
• Number Of I /o: 22
• Program Memory Size: 128KB (64K x 16)
• Program Memory Type: FLASH
• Ram Size: 3.8K x 8
• Voltage - Supply (vcc/vdd): 2.15 V ~ 3.6 V
• Data Converters: A/D 10x10b/12b
• Oscillator Type: Internal
• Operating Temperature: -40°C ~ 85°C
• Package / Case: *
• Processor Series: PIC18F
• Core: PIC
• Data Bus Width: 8 bit
• Data Ram Size: 3.8 KB
• Interface Type: I2C, SPI, USART
• Maximum Clock Frequency: 48 MHz
• Number Of Programmable I/os: 16
• Number Of Timers: 8
• Operating Supply Voltage: 2.15 V to 3.6 V
• Maximum Operating Temperature: + 85 C
• Mounting Style: SMD/SMT
• Minimum Operating Temperature: - 40 C
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Eeprom Size: -
• Lead Free Status / Rohs Status: Details

10.7.3.3
The control schema of the PPS is extremely flexible.
Other than systematic blocks that prevent signal con-
tention caused by two physical pins being configured
as the same functional input or two functional outputs
configured as the same pin, there are no hardware
enforced lockouts. The flexibility extends to the point of
allowing a single input to drive multiple peripherals or a
single functional output to drive multiple output pins.
10.7.4
Because peripheral remapping can be changed during
run time, some restrictions on peripheral remapping
are needed to prevent accidental configuration
changes. PIC18F devices include three features to
prevent alterations to the peripheral map:
• Control register lock sequence
• Continuous state monitoring
• Configuration bit remapping lock
10.7.4.1
Under normal operation, writes to the RPINRx and
RPORx registers are not allowed. Attempted writes will
appear to execute normally, but the contents of the
registers will remain unchanged. To change these reg-
isters, they must be unlocked in hardware. The register
lock is controlled by the IOLOCK bit (PPSCON<0>).
Setting IOLOCK prevents writes to the control
registers; clearing IOLOCK allows writes.
To set or clear IOLOCK, a specific command sequence
must be executed:
1.
2.
3.
IOLOCK remains in one state until changed. This
allows all of the PPS registers to be configured with a
single unlock sequence followed by an update to all
control registers, then locked with a second lock
sequence.
10.7.4.2
In addition to being protected from direct writes, the
contents of the RPINRx and RPORx registers are
constantly monitored in hardware by shadow registers.
If an unexpected change in any of the registers occurs
(such as cell disturbances caused by ESD or other
external events), a Configuration Mismatch Reset will
be triggered.
 2010 Microchip Technology Inc.
Write 55h to EECON2<7:0>.
Write AAh to EECON2<7:0>.
Clear (or set) IOLOCK as a single operation.
CONTROLLING CONFIGURATION
CHANGES
Mapping Limitations
Control Register Lock
Continuous State Monitoring
Preliminary
PIC18F47J53 FAMILY
10.7.4.3
As an additional level of safety, the device can be con-
figured to prevent more than one write session to the
RPINRx and RPORx registers. The IOL1WAY
(CONFIG3H<0>) Configuration bit blocks the IOLOCK
bit from being cleared after it has been set once. If
IOLOCK remains set, the register unlock procedure will
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. Programming
IOL1WAY allows users unlimited access (with the
proper use of the unlock sequence) to the PPS
registers.
10.7.5
The ability to control Peripheral Pin Selection intro-
duces several considerations into application design
that could be overlooked. This is particularly true for
several common peripherals that are available only as
remappable peripherals.
The main consideration is that the PPS is not available
on default pins in the device’s default (Reset) state.
Since all RPINRx registers reset to ‘11111’ and all
RPORx registers reset to ‘00000’, all PPS inputs are
tied to RP31 and all PPS outputs are disconnected.
This situation requires the user to initialize the device
with the proper peripheral configuration before any
other application code is executed. Since the IOLOCK
bit resets in the unlocked state, it is not necessary to
execute the unlock sequence after the device has
come out of Reset.
For application safety, however, it is best to set
IOLOCK and lock the configuration after writing to the
control registers.
The unlock sequence is timing-critical. Therefore, it is
recommended that the unlock sequence be executed
as an assembly language routine with interrupts
temporarily disabled. If the bulk of the application is
written in C or another high-level language, the unlock
sequence should be performed by writing in-line
assembly.
Note:
CONSIDERATIONS FOR
PERIPHERAL PIN SELECTION
In tying PPS inputs to RP31, RP31 does
not have to exist on a device for the
registers to be reset to it.
Configuration Bit Pin Select Lock
DS39964B-page 163