PIC18F23K20-E/MLQTP MICROCHIP [Microchip Technology], PIC18F23K20-E/MLQTP Datasheet - Page 53

• Manufacturer Part Number: PIC18F23K20-E/MLQTP
• Description: 28/40/44-Pin Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology
• Manufacturer: MICROCHIP [Microchip Technology]

4.2
The MCLR pin provides a method for triggering an
external Reset of the device. A Reset is generated by
holding the pin low. These 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.
In PIC18F2XK20/4XK20 devices, the MCLR input can
be disabled with the MCLRE Configuration bit. When
MCLR is disabled, the pin becomes a digital input. See
Section 10.6 “PORTE, TRISE and LATE Registers”
for more information.
4.3
A Power-on Reset pulse 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 condition), device operating parameters (volt-
age, 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.
POR events are captured by the POR bit of the RCON
register. The state of the bit is set to ‘0’ whenever a
POR 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 must manually set
the bit to ‘1’ by software following any POR.
© 2007 Microchip Technology Inc.
DD
DD
is adequate for operation.
is specified (parameter D004). For a slow rise
Master Clear (MCLR)
Power-on Reset (POR)
DD
rises above a certain threshold. This
DD
Advance Information
. This will
FIGURE 4-2:
PIC18F2XK20/4XK20
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
D
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
MCLR
PIC
POWER-UP)
DS41303B-page 51
®
MCU