PIC18F010 datasheet(10/176 Pages) MICROCHIP

10 / 176 page

PIC18F010/020

DS41142A-page 8

Preliminary

 2001 Microchip Technology Inc.

TABLE 2-1:

CERAMIC RESONATORS

TABLE 2-2:

CAPACITOR SELECTION FOR

CRYSTAL OSCILLATOR

2.3

RC Oscillator

For applications where precise timing is not a require-

ment, the RC and RCIO oscillator options are available.

The operation and functionality of the RC oscillator is

dependent on a number of variables. The RC oscillator

is a function of the supply voltage, the resistor (REXT)

and capacitor (CEXT) values, and the operating temper-

ature. The oscillator frequency will vary from unit to unit

due to normal process parameter variation. Plus, the

difference in lead frame capacitance between package

types will also affect the oscillation frequency, espe-

cially for low CEXT values. The user also needs to

account for the tolerance of the external R and C com-

ponents. Figure 2-3 shows how the R/C combination is

connected.

FIGURE 2-3:

RC OSCILLATOR MODE

In the RC mode, the oscillator frequency divided by 4 is

available on the OSC2 pin. This signal may be used for

test purposes, or to synchronize other logic. In the

RCIO mode, the OSC2 pin becomes a general purpose

I/O pin. This pin is RB4 of PORTB.

2.4

The Internal Oscillator

The INTOSC and INTOSCIO device options are avail-

able to minimize part count and cost, while maximizing

the number of I/O pins. There are five different frequen-

cies of which the user has the option to select. They are

32 kHz, 500 kHz, 1 MHz, 4 MHz, and 8 MHz. The 1

MHz, 4 MHz, and 8 MHz internal clock selections are

all derived from one 8 MHz clock source, and the other

two are produced independently. Tuning is available for

the 1 MHz, 4 MHz, and 8 MHz options; refer to

Section 2.10.

Ranges Tested:

Mode

Freq.

OSC1

OSC2

455 kHz

2.0 MHz

4.0 MHz

68 - 100 pF

15 - 68 pF

68 - 100 pF

15 - 68 pF

8.0 MHz

16.0 MHz

10 - 68 pF

10 - 22 pF

10 - 68 pF

10 - 22 pF

These values are for design guidance only.

See notes at bottom of page.

Resonators Used:

455 kHz

Panasonic EFO-A455K04B

± 0.3%

2.0 MHz

Murata Erie CSA2.00MG

± 0.5%

4.0 MHz

Murata Erie CSA4.00MG

± 0.5%

8.0 MHz

Murata Erie CSA8.00MT

± 0.5%

16.0 MHz

Murata Erie CSA16.00MX

± 0.5%

All resonators used did not have built-in capacitors.

Osc Type

Crystal

Freq.

Cap. Range

Cap.

Range C2

32.0 kHz

33 pF

200 kHz

15 pF

200 kHz

47-68 pF

1.0 MHz

15 pF

4.0 MHz

15 pF

4.0 MHz

15 pF

8.0 MHz

15-33 pF

20.0 MHz

15-33 pF

25.0 MHz

TBD

These values are for design guidance only.

See notes at bottom of page.

Crystals Used

32.0 kHz

Epson C-001R32.768K-A

± 20 PPM

200 kHz

STD XTL 200.000KHz

± 20 PPM

1.0 MHz

ECS ECS-10-13-1

± 50 PPM

4.0 MHz

ECS ECS-40-20-1

± 50 PPM

8.0 MHz

EPSON CA-301 8.000M-C

± 30 PPM

20.0 MHz

EPSON CA-301 20.000M-C

± 30 PPM

Note 1: Recommended values of C1 and C2 are

identical to the ranges tested (Table 2-1).

2: Higher capacitance increases the stability

of the oscillator, but also increases the

start-up time.

3: Since each resonator/crystal has its own

characteristics, the user should consult the

resonator/crystal manufacturer for appro-

priate values of external components.

4: Rs may be required in HS mode, as well as

XT mode, to avoid overdriving crystals with

low drive level specification.

Note:

The RC oscillator is not recommended for

applications that require precise timing.

OSC2/CLKO

CEXT

REXT

PIC18F010/020

OSC1

FOSC/4

Internal

Clock

VDD

VSS

Recommended values:

3 k

Ω ≤ REXT ≤ 100 kΩ

CEXT > 20pF

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