PIC16LC924-08/CL View Datasheet(PDF) - Microchip Technology

Part Name

Description

Manufacturer

PIC16LC924-08/CL

8-Bit CMOS Microcontroller with LCD Driver

Microchip Technology 

PIC16C9XX

14.3 Reset

The PIC16CXX differentiates between various kinds of

reset:

• Power-on Reset (POR)

• MCLR Reset during normal operation

• MCLR Reset during SLEEP

• WDT Reset (normal operation)

Some registers are not affected in any reset condition;

their status is unknown on POR and unchanged in any

other reset. Most other registers are reset to a “reset

state” on Power-on Reset (POR), on the MCLR and

WDT Reset, and on MCLR Reset during SLEEP. They

are not affected by a WDT Wake-up, which is viewed as

the resumption of normal operation. The TO and PD

bits are set or cleared differently in different reset situ-

ations as indicated in Table 14-4. These bits are used

in software to determine the nature of the reset. See

Table 14-6 for a full description of reset states of all reg-

isters.

A simplified block diagram of the on-chip reset circuit is

shown in Figure 14-7.

The devices all have a MCLR noise filter in the MCLR

reset path. The filter will detect and ignore small pulses.

It should be noted that a WDT Reset does not drive

MCLR pin low.

FIGURE 14-7: SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT

External

Reset

MCLR

VDD

SLEEP

WDT WDT

Module Time-out

VDD rise

detect

Power-on Reset

S

OST/PWRT

OST

10-bit Ripple counter

R

OSC1

(1) PWRT

On-chip

RC OSC

10-bit Ripple counter

Chip_Reset

Q

Enable PWRT(2)

Enable OST(2)

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

2: See Table 14-3 for time-out situations.

DS30444E - page 106

© 1997 Microchip Technology Inc.

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