PIC18LF8520-IPT301 View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC18LF8520-IPT301

64/80-Pin High-Performance, 256 Kbit to 1 MbitEnhanced Flash Microcontrollers with A/D

Microchip Technology 

PIC18F6520/8520/6620/8620/6720/8720

3.0 RESET

The PIC18FXX20 devices differentiate between

various kinds of Reset:

a) Power-on Reset (POR)

b) MCLR Reset during normal operation

c) MCLR Reset during Sleep

d) Watchdog Timer (WDT) Reset (during normal

operation)

e) Programmable Brown-out Reset (PBOR)

f) RESET Instruction

g) Stack Full Reset

h) Stack Underflow Reset

Most registers are unaffected by a Reset. Their status

is unknown on POR and unchanged by all other

Resets. The other registers are forced to a “Reset

state” on Power-on Reset, MCLR, WDT Reset, Brown-

out Reset, MCLR Reset during Sleep and by the

RESET instruction.

Most registers are not affected by a WDT wake-up,

since this is viewed as the resumption of normal

operation. Status bits from the RCON register, RI, TO,

PD, POR and BOR, are set or cleared differently in

different Reset situations, as indicated in Table 3-2.

These bits are used in software to determine the nature

of the Reset. See Table 3-3 for a full description of the

Reset states of all registers.

A simplified block diagram of the On-Chip Reset Circuit

is shown in Figure 3-1.

The Enhanced MCU devices have a MCLR noise filter

in the MCLR Reset path. The filter will detect and

ignore small pulses. The MCLR pin is not driven low by

any internal Resets, including the WDT.

FIGURE 3-1:

SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT

RESET Instruction

Stack Stack Full/Underflow Reset

Pointer

MCLR

VDD

OSC1

External Reset

WDT

Module

WDT

Time-out

Reset

Sleep

VDD Rise Power-on Reset

Detect

Brown-out

Reset

BOREN

OST/PWRT

OST

10-bit Ripple Counter

S

Chip_Reset

R

Q

PWRT

On-chip

RC OSC(1)

10-bit Ripple Counter

Enable PWRT

Note 1: This is a separate oscillator from the RC oscillator of the CLKI pin.

2: See Table 3-1 for time-out situations.

Enable OST(2)

 2003-2013 Microchip Technology Inc.

DS39609C-page 29

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