PIC18F1320T-E/SOSQTP 데이터 시트보기 (PDF) - Microchip Technology

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PIC18F1320T-E/SOSQTP

18/20/28-Pin High-Performance, Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology

Microchip Technology 

2.4 External Clock Input

The EC and ECIO Oscillator modes require an external

clock source to be connected to the OSC1 pin. There is

no oscillator start-up time required after a Power-on

Reset, or after an exit from Sleep mode.

In the EC Oscillator 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. Figure 2-4 shows the pin connections for the EC

Oscillator mode.

FIGURE 2-4:

EXTERNAL CLOCK INPUT

OPERATION

(EC CONFIGURATION)

Clock from

Ext. System

FOSC/4

OSC1/CLKI

PIC18FXXXX

OSC2/CLKO

The ECIO Oscillator mode functions like the EC mode,

except that the OSC2 pin becomes an additional gen-

eral purpose I/O pin. The I/O pin becomes bit 6 of

PORTA (RA6). Figure 2-5 shows the pin connections

for the ECIO Oscillator mode.

FIGURE 2-5:

EXTERNAL CLOCK INPUT

OPERATION

(ECIO CONFIGURATION)

Clock from

Ext. System

RA6

OSC1/CLKI

PIC18FXXXX

I/O (OSC2)

PIC18F1220/1320

2.5 RC Oscillator

For timing insensitive applications, the “RC” and

“RCIO” device options offer additional cost savings.

The RC oscillator frequency is a function of the supply

voltage, the resistor (REXT) and capacitor (CEXT) val-

ues and the operating temperature. In addition to this,

the oscillator frequency will vary from unit to unit due to

normal manufacturing variation. Furthermore, the dif-

ference in lead frame capacitance between package

types will also affect the oscillation frequency, espe-

cially for low CEXT values. The user also needs to take

into account variation, due to tolerance of external

R and C components used. Figure 2-6 shows how the

R/C combination is connected.

In the RC Oscillator 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.

FIGURE 2-6:

VDD

RC OSCILLATOR MODE

REXT

OSC1

Internal

Clock

CEXT

VSS

OSC2/CLKO

FOSC/4

PIC18FXXXX

Recommended values: 3 kΩ ≤ REXT ≤ 100 kΩ

CEXT > 20 pF

The RCIO Oscillator mode (Figure 2-7) functions like

the RC mode, except that the OSC2 pin becomes an

additional general purpose I/O pin. The I/O pin

becomes bit 6 of PORTA (RA6).

FIGURE 2-7:

VDD

RCIO OSCILLATOR MODE

REXT

CEXT

VSS

RA6

OSC1

Internal

Clock

I/O (OSC2)

PIC18FXXXX

Recommended values: 3 kΩ ≤ REXT ≤ 100 kΩ

CEXT > 20 pF

© 2007 Microchip Technology Inc.

DS39605F-page 13

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