DV164136 Microchip Technology, DV164136 Datasheet - Page 53

• Manufacturer Part Number: DV164136
• Description: DEVELOPMENT KIT FOR PIC18
• Manufacturer: Microchip Technology
• Series: PIC®r
• Type: MCUr

Specifications of DV164136

• Contents: Board, Cables, CDs, PICkit™ 3 Programmer, Power Supply
• Processor To Be Evaluated: PIC18F8722, PIC18F87J11
• Interface Type: RS-232, USB
• Operating Supply Voltage: 3.3 V, 5 V
• Silicon Manufacturer: Microchip
• Core Architecture: PIC
• Core Sub-architecture: PIC18
• Silicon Core Number: PIC18F
• Silicon Family Name: PIC18F8xxx
• Kit Contents: PIC18 Exp Brd PICkit 3 Cable CD PSU
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• For Use With/related Products: PIC18F8722, PIC18F87J11
• Lead Free Status / Rohs Status: Lead free / RoHS Compliant

4.2
The MCLR pin provides a method for triggering a hard
external Reset of the device. A Reset is generated by
holding the pin low. PIC18 extended microcontroller
devices have a noise filter in the MCLR Reset path
which detects and ignores small pulses.
The MCLR pin is not driven low by any internal Resets,
including the WDT.
4.3
A Power-on Reset condition is generated on-chip
whenever V
allows the device to start in the initialized state when
V
To take advantage of the POR circuitry, tie the MCLR
pin through a resistor (1 kΩ to 10 kΩ) to V
eliminate external RC components usually needed to
create a Power-on Reset delay. A minimum rise rate for
V
time, see Figure 4-2.
When the device starts normal operation (i.e., exits the
Reset
(voltage, frequency, temperature, etc.) must be met to
ensure operation. If these conditions are not met, the
device must be held in Reset until the operating
conditions are met.
Power-on Reset events are captured by the POR bit
(RCON<1>). The state of the bit is set to ‘0’ whenever
a Power-on Reset occurs; it does not change for any
other Reset event. POR is not reset to ‘1’ by any
hardware event. To capture multiple events, the user
manually resets the bit to ‘1’ in software following any
Power-on Reset.
4.4
The PIC18F87J11 family of devices incorporates a
simple Brown-out Reset function when the internal reg-
ulator is enabled (ENVREG pin is tied to V
drop of V
than time T
Reset may or may not occur if V
less than T
Reset until V
Once a Brown-out Reset has occurred, the Power-up
Timer will keep the chip in Reset for T
(parameter 33). If V
Power-up Timer is running, the chip will go back into a
Brown-out Reset and the Power-up Timer will be
initialized. Once V
Timer will execute the additional time delay.
© 2009 Microchip Technology Inc.
DD
DD
is adequate for operation.
is specified (parameter D004). For a slow rise
condition),
Master Clear (MCLR)
Power-on Reset (POR)
Brown-out Reset (BOR)
DD
BOR
DD
below V
BOR
DD
rises above a certain threshold. This
(parameter 35) will reset the device. A
. The chip will remain in Brown-out
rises above V
DD
BOR
DD
device
rises above V
drops below V
(parameter D005)) for greater
BOR
operating
DD
.
falls below V
BOR
, the Power-up
BOR
DD
parameters
. This will
while the
DD
BOR
). Any
PWRT
for
PIC18F87J11 FAMILY
FIGURE 4-2:
4.4.1
The BOR bit always resets to ‘0’ on any Brown-out
Reset or Power-on Reset event. This makes it difficult
to determine if a Brown-out Reset event has occurred
just by reading the state of BOR alone. A more reliable
method is to simultaneously check the state of both
POR and BOR. This assumes that the POR bit is reset
to ‘1’ in software immediately after any Power-on Reset
event. If BOR is ‘0’ while POR is ‘1’, it can be reliably
assumed that a Brown-out Reset event has occurred.
If the voltage regulator is disabled, Brown-out Reset
functionality is disabled. In this case, the BOR bit
cannot be used to determine a Brown-out Reset event.
The BOR bit is still cleared by a Power-on Reset event.
4.5
The Configuration Mismatch (CM) Reset is designed to
detect and attempt to recover from random, memory
corrupting events. These include Electrostatic Discharge
(ESD) events, which can cause widespread, single-bit
changes throughout the device and result in catastrophic
failure.
In PIC18FXXJ Flash devices, the device Configuration
registers (located in the configuration memory space)
are continuously monitored during operation by
comparing their values to complimentary shadow reg-
isters. 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;
it does not change for any other Reset event.
Note 1: External Power-on Reset circuit is required
V
2: R < 40 kΩ is recommended to make sure that
3: R1 ≥ 1 kΩ will limit any current flowing into
DD
Configuration Mismatch (CM)
D
DETECTING BOR
only if the V
The diode D helps discharge the capacitor
quickly when V
the voltage drop across R does not violate
the device’s electrical specification.
MCLR from external capacitor C, in the event
of MCLR/V
Electrostatic Discharge (ESD) or Electrical
Overstress (EOS).
V
DD
R
C
EXTERNAL POWER-ON
RESET CIRCUIT (FOR
SLOW V
DD
PP
R1
DD
power-up slope is too slow.
pin breakdown, due to
powers down.
DD
PIC18F87J11
MCLR
POWER-UP)
DS39778D-page 53