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PIC18F4431-I/PT 参数 Datasheet PDF下载

PIC18F4431-I/PT图片预览
型号: PIC18F4431-I/PT
PDF下载: 下载PDF文件 查看货源
内容描述: 28 /40/ 44引脚增强型闪存微控制器采用纳瓦技术,高性能PWM和A / D [28/40/44-Pin Enhanced Flash Microcontrollers with nanoWatt Technology, High-Performance PWM and A/D]
分类和应用: 闪存微控制器
文件页数/大小: 392 页 / 3127 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC18F2331/2431/4331/4431  
3.4  
External Clock Input  
3.5  
RC Oscillator  
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.  
For timing-insensitive applications, the “RC” and “RCIO”  
device options offer additional cost savings. The actual  
oscillator frequency is a function of several factors:  
• Supply voltage  
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 3-4 shows the pin connections for the EC  
Oscillator mode.  
• Values of the external resistor (REXT) and capacitor  
(CEXT)  
• Operating temperature  
Given the same device, operating voltage and tempera-  
ture, and component values, there will also be unit-to-unit  
frequency variations. These are due to factors, such as:  
FIGURE 3-4:  
EXTERNAL CLOCK INPUT  
OPERATION  
• Normal manufacturing variation  
• Difference in lead frame capacitance between  
package types (especially for low CEXT values)  
(EC CONFIGURATION)  
• Variations within the tolerance of limits of REXT  
and CEXT  
OSC1/CLKI  
Clock from  
Ext. System  
PIC18FXXXX  
OSC2/CLKO  
In the RC Oscillator mode (Figure 3-6), 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.  
FOSC/4  
The ECIO Oscillator mode functions like the EC 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 3-5 shows the pin connections  
for the ECIO Oscillator mode.  
FIGURE 3-6:  
RC OSCILLATOR MODE  
VDD  
REXT  
Internal  
OSC1  
FIGURE 3-5:  
EXTERNAL CLOCK INPUT  
OPERATION  
Clock  
(ECIO CONFIGURATION)  
CEXT  
VSS  
PIC18FXXXX  
OSC2/CLKO  
OSC1/CLKI  
PIC18FXXXX  
I/O (OSC2)  
Clock from  
Ext. System  
FOSC/4  
Recommended values: 3 k  REXT 100 k  
RA6  
CEXT > 20 pF  
The RCIO Oscillator mode (Figure 3-7) 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 3-7:  
RCIO OSCILLATOR MODE  
VDD  
REXT  
Internal  
OSC1  
Clock  
CEXT  
PIC18FXXXX  
VSS  
I/O (OSC2)  
RA6  
Recommended values: 3 k  REXT 100 k  
CEXT > 20 pF  
2010 Microchip Technology Inc.  
DS39616D-page 31  
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