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ATMEGA2560-16AU-SL383 参数 Datasheet PDF下载

ATMEGA2560-16AU-SL383图片预览
型号: ATMEGA2560-16AU-SL383
PDF下载: 下载PDF文件 查看货源
内容描述: [Microcontroller, 8-Bit, FLASH, AVR RISC CPU, 16MHz, CMOS, PQFP100, 14 X 14 MM, 1 MM HEIGHT, 0.50 MM PITCH, GREEN, PLASTIC, MS-026AED, TQFP-100]
分类和应用: 时钟微控制器
文件页数/大小: 448 页 / 7518 K
品牌: ATMEL [ ATMEL ]
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ATmega640/1280/1281/2560/2561  
Figure 20-10. Timer/Counter Timing Diagram, Setting of OCF2A, with Prescaler (fclk_I/O/8)  
clkI/O  
clkTn  
(clkI/O/8)  
TCNTn  
OCRnx  
OCFnx  
OCRnx - 1  
OCRnx  
OCRnx + 1  
OCRnx + 2  
OCRnx Value  
Figure 20-11 shows the setting of OCF2A and the clearing of TCNT2 in CTC mode.  
Figure 20-11. Timer/Counter Timing Diagram, Clear Timer on Compare Match mode, with Pres-  
caler (fclk_I/O/8)  
clkI/O  
clkTn  
(clkI/O/8)  
TCNTn  
(CTC)  
TOP - 1  
TOP  
BOTTOM  
BOTTOM + 1  
OCRnx  
TOP  
OCFnx  
20.8 Asynchronous Operation of Timer/Counter2  
When Timer/Counter2 operates asynchronously, some considerations must be taken.  
Warning: When switching between asynchronous and synchronous clocking of  
Timer/Counter2, the Timer Registers TCNT2, OCR2x, and TCCR2x might be corrupted. A  
safe procedure for switching clock source is:  
1. Disable the Timer/Counter2 interrupts by clearing OCIE2x and TOIE2.  
2. Select clock source by setting AS2 as appropriate.  
3. Write new values to TCNT2, OCR2x, and TCCR2x.  
4. To switch to asynchronous operation: Wait for TCN2UB, OCR2xUB, and TCR2xUB.  
5. Clear the Timer/Counter2 Interrupt Flags.  
6. Enable interrupts, if needed.  
The CPU main clock frequency must be more than four times the Oscillator frequency.  
When writing to one of the registers TCNT2, OCR2x, or TCCR2x, the value is transferred to  
a temporary register, and latched after two positive edges on TOSC1. The user should not  
185  
2549L–AVR–08/07  
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