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68HC705JJ7_1 参数 Datasheet PDF下载

68HC705JJ7_1图片预览
型号: 68HC705JJ7_1
PDF下载: 下载PDF文件 查看货源
内容描述: 常规版本规格 [General Release Specification]
分类和应用:
文件页数/大小: 230 页 / 5548 K
品牌: FREESCALE [ Freescale ]
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Freescale Semiconductor, Inc.  
Ana log Sub syste m  
8.2 Introd uc tion  
The analog subsystem of the MC68HC705JJ7/MC68HC705JP7 is  
based on two on-chip voltage comparators and a selectable current  
charge/discharge function as shown in Figure 8-1.  
This configuration provides several features:  
• Two (2) independent voltage comparators with external access to  
both inverting and non-inverting inputs  
• One voltage comparator can be connected as a single-slope A/D  
and the other connected as a single-voltage comparator. The  
possible single-slope A/D connection provides the following  
features:  
– A/D conversions can use V or an external voltage as a  
DD  
reference with software used to calculate ratiometric or  
absolute results  
– Channel access of up to four inputs via multiplexer control with  
independent multiplexer control allowing mixed input  
connections  
– Access to V and V for calibration  
DD  
SS  
– Divide by 2 to extend input voltage range  
– Each comparator can be inverted to calculate input offsets  
– Internal sample and hold capacitor  
– direct digital output of comparator 1 to the PB4 pin  
Voltages are resolved by measuring the time it takes an external  
capacitor to charge up to the level of the unknown input voltage being  
measured. The beginning of the A/D conversion time can be started by  
several means:  
• Output compare from the 16-bit programmable timer  
• Timer overflow from the 16-bit programmable timer  
• Direct software control via a register bit  
The end of the A/D conversion time can be captured by these means:  
• Input capture in the 16-bit programmable timer  
• Interrupt generated by the comparator output  
• Software polling of the comparator output using software loop time  
General Release Specification  
MC68HC705JJ7/MC68HC705JP7 Rev. 3.0  
Analog Subsystem  
For More Information On This Product,  
Go to: www.freescale.com  
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