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參數(shù)資料
| 型號： | pic12ce674 |
| 廠商： | Microchip Technology Inc. |
| 英文描述： | 8-Pin, 8-Bit CMOS Microcontroller with A/D Converter(具A/D轉(zhuǎn)換器和EEPROM數(shù)據(jù)存儲器的8位微控制器) |
| 中文描述： | 8引腳，8位CMOS微控制器與A / D轉(zhuǎn)換器（具的A / D轉(zhuǎn)換器和EEPROM的數(shù)據(jù)存儲器的8位微控制器） |
| 文件頁數(shù)： | 33/112頁 |
| 文件大?。?/td> | 1205K |
| 代理商： | PIC12CE674 |
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1998 Microchip Technology Inc.
Preliminary
DS40181A-page 33
PIC12CE67X
7.2
When an external clock input is used for Timer0, it must
meet certain requirements. The requirements ensure
the external clock can be synchronized with the internal
phase clock (T
OSC
). Also, there is a delay in the actual
incrementing of Timer0 after synchronization.
Using Timer0 with an External Clock
7.2.1
EXTERNAL CLOCK SYNCHRONIZATION
When no prescaler is used, the external clock input is
the same as the prescaler output. The synchronization
of T0CKI with the internal phase clocks is accom-
plished by sampling the prescaler output on the Q2 and
Q4 cycles of the internal phase clocks (Figure 7-5).
Therefore, it is necessary for T0CKI to be high for at
least 2Tosc (and a small RC delay of 20 ns) and low for
at least 2Tosc (and a small RC delay of 20 ns). Refer to
the electrical specification of the desired device.
When a prescaler is used, the external clock input is
divided by the asynchronous ripple-counter type pres-
caler so that the prescaler output is symmetrical. For
the external clock to meet the sampling requirement,
the ripple-counter must be taken into account. There-
fore, it is necessary for T0CKI to have a period of at
least 4Tosc (and a small RC delay of 40 ns) divided by
the prescaler value. The only requirement on T0CKI
high and low time is that they do not violate the mini-
mum pulse width requirement of 10 ns. Refer to param-
eters 40, 41 and 42 in the electrical specification of the
desired device.
7.2.2
Since the prescaler output is synchronized with the
internal clocks, there is a small delay from the time the
external clock edge occurs to the time the Timer0 mod-
ule is actually incremented. Figure 7-5 shows the delay
from the external clock edge to the timer incrementing.
TMR0 INCREMENT DELAY
FIGURE 7-5:
TIMER0 TIMING WITH EXTERNAL CLOCK
Q1
Q2
Q3 Q4
Q1
Q2
Q3 Q4
Q1
Q2
Q3 Q4
Q1
Q2
Q3 Q4
Small pulse
misses sampling
External Clock Input or
Prescaler output
External Clock/Prescaler
Output after sampling
Increment Timer0 (Q4)
Timer0
T0
T0 + 1
T0 + 2
Note 1: Delay from clock input change to Timer0 increment is 3Tosc to 7Tosc. (Duration of Q = Tosc).
Therefore, the error in measuring the interval between two edges on Timer0 input =
±
4Tosc max.
2: External clock if no prescaler selected, Prescaler output otherwise.
3: The arrows indicate the points in time where sampling occurs.
(3)
(1)
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| PIC12CE674/JW | 功能描述:8位微控制器 -MCU 3.5KB 128 RAM 6 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
| PIC12CE674-04/JM | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontroller with A/D Converter |
| PIC12CE674-04/JW | 制造商:MICROCHIP 制造商全稱:Microchip Technology 功能描述:8-Pin, 8-Bit CMOS Microcontroller with A/D Converter and EEPROM Data Memory |
| PIC12CE674-04/P | 功能描述:8位微控制器 -MCU 3.5KB 128 RAM 6 I/O RoHS:否 制造商:Silicon Labs 核心:8051 處理器系列:C8051F39x 數(shù)據(jù)總線寬度:8 bit 最大時鐘頻率:50 MHz 程序存儲器大小:16 KB 數(shù)據(jù) RAM 大小:1 KB 片上 ADC:Yes 工作電源電壓:1.8 V to 3.6 V 工作溫度范圍:- 40 C to + 105 C 封裝 / 箱體:QFN-20 安裝風(fēng)格:SMD/SMT |
| PIC12CE674-04/P | 制造商:Microchip Technology Inc 功能描述:IC 8BIT CMOS MCU 12CE674 DIP8 |
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