PIC12F635ESS datasheet(133/234 Pages) MICROCHIP

133 / 234 page

DS41232D-page 131

PIC12F635/PIC16F636/639

12.2

Reset

The PIC12F635/PIC16F636/639 differentiates between

various kinds of Reset:

Power-on Reset (POR)

Wake-up Reset (WUR)

WDT Reset during normal operation

WDT Reset during Sleep

MCLR Reset during normal operation

MCLR Reset during Sleep

Brown-out Reset (BOR)

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

•MCLR Reset

•MCLR Reset during Sleep

•WDT Reset

• Brown-out Reset

They are not affected by a WDT wake-up since this is

viewed as the resumption of normal operation. TO and

PD bits are set or cleared differently in different Reset

situations, as indicated in Table 12-3. These bits are

used in software to determine the nature of the Reset.

See Table 12-4 for a full description of Reset states of

all registers.

A simplified block diagram of the On-Chip Reset Circuit

is shown in Figure 12-1.

The MCLR Reset path has a noise filter to detect and

ignore small pulses. See Section 15.0 “Electrical

Specifications” for pulse width specifications.

FIGURE 12-1:

SIMPLIFIED BLOCK DIAGRAM OF ON-CHIP RESET CIRCUIT

External Reset

MCLR/VPP pin

VDD

OSC1/

WDT

Module

VDD Rise

Detect

OST/PWRT

LFINTOSC

WDT

Time-out

Power-on Reset

OST

10-bit Ripple Counter

PWRT

Chip_Reset

11-bit Ripple Counter

Reset

Enable OST

Enable PWRT

Sleep

Brown-out(1)

Reset

SBOREN

BOREN<0>

CLKI pin

Note

Refer to the Configuration Word register (Register 12-1).

Sleep

WURE

RA3 Change

Wake-up Interrupt

BOREN

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