PIC16C72-04SLASHSP datasheet(61/124 Pages) MICROCHIP

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PIC16C72 Series

Preliminary

DS39016A-page 61

10.2.3

RC OSCILLATOR

For timing insensitive applications the “RC” device

option offers additional cost savings. The RC oscillator

frequency is a function of the supply voltage, the resis-

tor (REXT) and capacitor (CEXT) values, and the operat-

ing temperature. In addition to this, the oscillator

frequency will vary from unit to unit due to normal pro-

cess parameter variation. Furthermore, the difference

in lead frame capacitance between package types will

also affect the oscillation frequency, especially for low

CEXT values. The user also needs to take into account

variation due to tolerance of external R and C compo-

nents used. Figure 10-4 shows how the R/C combina-

tion is connected to the PIC16CXXX family.

FIGURE 10-4: RC OSCILLATOR MODE

10.3

Reset

The PIC16CXXX family differentiates between various

kinds of reset:

• Power-on Reset (POR)

• MCLR reset during normal operation

• MCLR reset during SLEEP

• WDT Reset (normal operation)

• 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 (POR), on the MCLR and

WDT Reset, on MCLR reset during SLEEP, and Brown-

out Reset (BOR). 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 differ-

ently in different reset situations as indicated in

Table 10-4. These bits are used in software to deter-

mine the nature of the reset. See Table 10-6 for a full

description of reset states of all registers.

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

shown in Figure 10-5.

The PIC16C72/CR72 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.

OSC2/CLKOUT

Cext

Rext

PIC16CXXX

OSC1

Fosc/4

Internal

clock

VDD

VSS

Recommended values:

3 k

Ω ≤ Rext ≤ 100 kΩ

Cext > 20pF

PIC16C72-04/SP Datasheet(PDF) 61 Page - Microchip Technology

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