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器件3D模型￥ 20.347
PIC18F25K22-I/SO 数据手册 - Microchip（微芯）
制造商:
Microchip（微芯）
分类:
微控制器
封装:
SOIC-28
描述:
PIC18F2xK22/4xK22 8 位闪存微控制器### PIC18 微控制器
Pictures:
3D模型
符号图
焊盘图
引脚图
产品图
页面导航:
引脚图在P132P174P177P185Hot
典型应用电路图在P321P322
原理图在P14P26P28P42P55P155P156P157P160P169P174P177
封装尺寸在P512
标记信息在P509P510P511
封装信息在P509P513P514P515P517P521P522P525P526P527P528P529
技术参数、封装参数在P11P12P36P40P102P237P300P304P306P307P333P339
应用领域在P187P193P341
电气规格在P11P12P36P40P102P300P304P306P307P333P339
导航目录
PIC18F25K22-I/SO数据手册
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2010-2016 Microchip Technology Inc. DS40001412G-page 321
PIC18(L)F2X/4XK22
19.5 Measuring Time with the CTMU
Module
Time can be precisely measured after the ratio (C/I) is
measured from the current and capacitance calibration
step by following these steps:
1. Initialize the A/D Converter and the CTMU.
2. Set EDG1STAT.
3. Set EDG2STAT.
4. Perform an A/D conversion.
5. Calculate the time between edges as T = (C/I) * V,
where I is calculated in the current calibration step
(Section 19.3.1 “Current Source Calibration”),
C is calculated in the capacitance calibration step
(Section 19.3.2 “Capacitance Calibration”) and
V is measured by performing the A/D conversion.
It is assumed that the time measured is small enough
that the capacitance, C
OFFSET, provides a valid voltage
to the A/D Converter. For the smallest time measure-
ment, always set the A/D Channel Select register
(AD1CHS) to an unused A/D channel; the correspond-
ing pin for which is not connected to any circuit board
trace. This minimizes added stray capacitance, keep-
ing the total circuit capacitance close to that of the A/D
Converter itself (4-5 pF). To measure longer time
intervals, an external capacitor may be connected to an
A/D channel and this channel selected when making a
time measurement.
FIGURE 19-3: TYPICAL CONNECTIONS AND INTERNAL CONFIGURATION FOR TIME
MEASUREMENT
A/D Converter
CTMU
CTED1
CTED2
AN
X
Output
Pulse
EDG1
EDG2
CAD
RPR
Current Source
PIC18(L)FXXK22 Device
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