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PIC16F877T-20PQ 参数 Datasheet PDF下载

PIC16F877T-20PQ图片预览
型号: PIC16F877T-20PQ
PDF下载: 下载PDF文件 查看货源
内容描述: 8位微控制器\n [8-Bit Microcontroller ]
分类和应用: 微控制器
文件页数/大小: 200 页 / 3338 K
品牌: ETC [ ETC ]
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PIC16F87X  
For correct A/D conversions, the A/D conversion clock  
(TAD) must be selected to ensure a minimum TAD time  
of 1.6 µs.  
11.2  
Selecting the A/D Conversion Clock  
The A/D conversion time per bit is defined as TAD. The  
A/D conversion requires a minimum 12TAD per 10-bit  
conversion. The source of the A/D conversion clock is  
software selected. The four possible options for TAD  
are:  
Table 11-1shows the resultant TAD times derived from  
the device operating frequencies and the A/D clock  
source selected.  
• 2TOSC  
• 8TOSC  
• 32TOSC  
• Internal RC oscillator  
TABLE 11-1: TAD vs. MAXIMUM DEVICE OPERATING FREQUENCIES (STANDARD DEVICES (C))  
AD Clock Source (TAD)  
ADCS1:ADCS0  
Maximum Device Frequency  
Max.  
Operation  
2TOSC  
8TOSC  
00  
01  
10  
11  
1.25 MHz  
5 MHz  
32TOSC  
RC(1, 2, 3)  
20 MHz  
Note 1  
Note 1: The RC source has a typical TAD time of 4 µs but can vary between 2-6 µs.  
2: When the device frequencies are greater than 1 MHz, the RC A/D conversion clock source is only recommended for sleep  
operation.  
3: For extended voltage devices (LC), please refer to the Electrical Specifications section.  
11.3  
Configuring Analog Port Pins  
The ADCON1, and TRIS registers control the operation  
of the A/D port pins. The port pins that are desired as  
analog inputs must have their corresponding TRIS bits  
set (input). If the TRIS bit is cleared (output), the digital  
output level (VOH or VOL) will be converted.  
The A/D operation is independent of the state of the  
CHS2:CHS0 bits and the TRIS bits.  
Note 1: When reading the port register, any pin  
configured as an analog input channel will  
read as cleared (a low level). Pins config-  
ured as digital inputs will convert an ana-  
log input. Analog levels on a digitally  
configured input will not affect the conver-  
sion accuracy.  
2: Analog levels on any pin that is defined as  
a digital input (including the AN7:AN0  
pins), may cause the input buffer to con-  
sume current that is out of the device  
specifications.  
DS30292B-page 116  
1999 Microchip Technology Inc.