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PIC18F4520-I/PT 参数 Datasheet PDF下载

PIC18F4520-I/PT图片预览
型号: PIC18F4520-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与10位A / D和纳瓦技术 [28/40/44-Pin Enhanced Flash Microcontrollers with 10-Bit A/D and nanoWatt Technology]
分类和应用: 闪存微控制器
文件页数/大小: 412 页 / 6898 K
品牌: MICROCHIP [ MICROCHIP ]
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PIC18F2420/2520/4420/4520  
The CCPRxH register and a 2-bit internal latch are  
EQUATION 15-3:  
used to double-buffer the PWM duty cycle. This  
double-buffering is essential for glitchless PWM  
operation.  
FOSC  
log ---------------  
FPWM  
PWM Resolution (max)  
= ----------------------------- b i t s  
log(2)  
When the CCPRxH and 2-bit latch match TMR2,  
concatenated with an internal 2-bit Q clock or 2 bits of  
the TMR2 prescaler, the CCPx pin is cleared.  
Note:  
If the PWM duty cycle value is longer than  
the PWM period, the CCPx pin will not be  
cleared.  
The maximum PWM resolution (bits) for a given PWM  
frequency is given by the equation:  
TABLE 15-4: EXAMPLE PWM FREQUENCIES AND RESOLUTIONS AT 40 MHz  
PWM Frequency  
2.44 kHz  
9.77 kHz  
39.06 kHz 156.25 kHz 312.50 kHz 416.67 kHz  
Timer Prescaler (1, 4, 16)  
PR2 Value  
16  
FFh  
10  
4
1
1
3Fh  
8
1
1Fh  
7
1
FFh  
10  
FFh  
10  
17h  
6.58  
Maximum Resolution (bits)  
15.4.3  
PWM AUTO-SHUTDOWN  
(CCP1 ONLY)  
15.4.4  
SETUP FOR PWM OPERATION  
The following steps should be taken when configuring  
the CCP module for PWM operation:  
The PWM auto-shutdown features of the Enhanced CCP  
module are also available to CCP1 in 28-pin devices. The  
operation of this feature is discussed in detail in  
Section 16.4.7 “Enhanced PWM Auto-Shutdown”.  
1. Set the PWM period by writing to the PR2  
register.  
2. Set the PWM duty cycle by writing to the  
CCPRxL register and CCPxCON<5:4> bits.  
Auto-shutdown features are not available for CCP2.  
3. Make the CCPx pin an output by clearing the  
appropriate TRIS bit.  
4. Set the TMR2 prescale value, then enable  
Timer2 by writing to T2CON.  
5. Configure the CCPx module for PWM operation.  
© 2008 Microchip Technology Inc.  
DS39631E-page 145