Microchip Technology MCU PIC PIC18F87K22-I/PTRSL TQFP-80 MCP PIC18F87K22-I/PTRSL Data Sheet
Product codes
PIC18F87K22-I/PTRSL
PIC18F87K22 FAMILY
DS39960D-page 76
2009-2011 Microchip Technology Inc.
5.5
Configuration Mismatch (CM)
The Configuration Mismatch (CM) Reset is designed to
detect, and attempt to recover from, random, memory
corrupting events. These include Electrostatic Discharge
(ESD) events that can cause widespread, single bit
changes throughout the device and result in catastrophic
failure.
In PIC18F87K22 family Flash devices, the device
Configuration registers (located in the configuration
memory space) are continuously monitored during
operation by comparing their values to complimentary
shadow registers. If a mismatch is detected between
the two sets of registers, a CM Reset automatically
occurs. These events are captured by the CM bit
(RCON<5>). The state of the bit is set to ‘0’ whenever
a CM event occurs and does not change for any other
Reset event.
A CM Reset behaves similarly to a Master Clear Reset,
RESET
detect, and attempt to recover from, random, memory
corrupting events. These include Electrostatic Discharge
(ESD) events that can cause widespread, single bit
changes throughout the device and result in catastrophic
failure.
In PIC18F87K22 family Flash devices, the device
Configuration registers (located in the configuration
memory space) are continuously monitored during
operation by comparing their values to complimentary
shadow registers. If a mismatch is detected between
the two sets of registers, a CM Reset automatically
occurs. These events are captured by the CM bit
(RCON<5>). The state of the bit is set to ‘0’ whenever
a CM event occurs and does not change for any other
Reset event.
A CM Reset behaves similarly to a Master Clear Reset,
RESET
instruction, WDT time-out or Stack Event Reset.
As with all hard and power Reset events, the device
Configuration Words are reloaded from the Flash
Configuration Words in program memory as the device
restarts.
Configuration Words are reloaded from the Flash
Configuration Words in program memory as the device
restarts.
5.6
Power-up Timer (PWRT)
PIC18F87K22 family devices incorporate an on-chip
Power-up Timer (PWRT) to help regulate the Power-on
Reset process. The PWRT is enabled by setting the
PWRTEN bit (CONFIG2L<0>). The main function is to
ensure that the device voltage is stable before code is
executed.
The Power-up Timer (PWRT) of the PIC18F87K22
family devices is a 13-bit counter that uses the
LF-INTOSC source as the clock input. This yields an
approximate time interval of 2,048 x 32
Power-up Timer (PWRT) to help regulate the Power-on
Reset process. The PWRT is enabled by setting the
PWRTEN bit (CONFIG2L<0>). The main function is to
ensure that the device voltage is stable before code is
executed.
The Power-up Timer (PWRT) of the PIC18F87K22
family devices is a 13-bit counter that uses the
LF-INTOSC source as the clock input. This yields an
approximate time interval of 2,048 x 32
s = 66 ms.
While the PWRT is counting, the device is held in
Reset.
The power-up time delay depends on the LF-INTOSC
clock and will vary from chip-to-chip due to temperature
and process variation. See DC Parameter
Reset.
The power-up time delay depends on the LF-INTOSC
clock and will vary from chip-to-chip due to temperature
and process variation. See DC Parameter
for
details.
5.6.1
TIME-OUT SEQUENCE
If enabled, the PWRT time-out is invoked after the POR
pulse has cleared. The total time-out will vary based on
the status of the PWRT.
pulse has cleared. The total time-out will vary based on
the status of the PWRT.
and
all depict time-out
sequences on power-up with the Power-up Timer
enabled.
Since the time-outs occur from the POR pulse, if
MCLR is kept low long enough, the PWRT will expire.
Bringing MCLR high will begin execution immediately
(
enabled.
Since the time-outs occur from the POR pulse, if
MCLR is kept low long enough, the PWRT will expire.
Bringing MCLR high will begin execution immediately
(
). This is useful for testing purposes or for
synchronizing more than one PIC18 device operating
in parallel.
in parallel.
FIGURE 5-3:
TIME-OUT SEQUENCE ON POWER-UP (MCLR TIED TO V
DD
, V
DD
RISE < T
PWRT
)
T
PWRT
V
DD
MCLR
INTERNAL POR
PWRT TIME-OUT
INTERNAL RESET