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參數(shù)資料
| 型號： | R5F21274JFP |
| 元件分類： | 微控制器/微處理器 |
| 英文描述： | 16-BIT, FLASH, 20 MHz, MICROCONTROLLER, PQFP32 |
| 封裝： | 7 X 7 MM, 0.80 MM PITCH, PLASTIC, LQFP-32 |
| 文件頁數(shù)： | 9/52頁 |
| 文件大小： | 620K |
| 代理商： | R5F21274JFP |
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34
ATmega165A/PA/325A/PA/3250A/PA/645A/P/6450A/P [DATASHEET]
8285E–AVR–02/2013
9.8
Timer/Counter oscillator
Atmel ATmega169P uses the same XTAL oscillator for Low-frequency Oscillator and Timer/Counter Oscillator.
See ”Low-frequency XTAL Oscillator” on page 31 for details on the oscillator and XTAL requirements.
ATmega169P share the Timer/Counter Oscillator Pins (TOSC1 and TOSC2) with XTAL1 and XTAL2. When using
the Timer/Counter Oscillator, the system clock needs to be four times the oscillator frequency. Due to this and the
pin sharing, the Timer/Counter Oscillator can only be used when the Calibrated Internal RC Oscillator is selected
as system clock source.
Applying an external clock source to TOSC1 can be done if EXTCLK in the ASSR Register is written to logic one.
See ”Asynchronous operation of the Timer/Counter” on page 135 for further description on selecting external clock
as input instead of a 32.768kHz watch XTAL.
9.9
Clock output buffer
When the CKOUT Fuse is programmed, the system Clock will be output on CLKO. This mode is suitable when chip
clock is used to drive other circuits on the system. The clock will be output also during reset and the normal opera-
tion of I/O pin will be overridden when the fuse is programmed. Any clock source, including internal RC Oscillator,
can be selected when CLKO serves as clock output. If the System Clock Prescaler is used, it is the divided system
clock that is output when the CKOUT Fuse is programmed.
9.10
System clock prescaler
The Atmel ATmega165A/165PA/325A/325PA/3250A/3250PA/645A/645P/6450A/6450P system clock can be
divided by setting the ”CLKPR – Clock Prescale Register” on page 35. This feature can be used to decrease the
system clock frequency and power consumption when the requirement for processing power is low. This can be
used with all clock source options, and it will affect the clock frequency of the CPU and all synchronous peripher-
als. clk
9.10.1
Switching time
When switching between prescaler settings, the System Clock Prescaler ensures that no glitches occur in the clock
system and that no intermediate frequency is higher than neither the clock frequency corresponding to the previous
setting, nor the clock frequency corresponding to the new setting.
The ripple counter that implements the prescaler runs at the frequency of the undivided clock, which may be faster
than the CPU’s clock frequency. Hence, it is not possible to determine the state of the prescaler – even if it were
readable, and the exact time it takes to switch from one clock division to another cannot be exactly predicted.
From the time the CLKPS values are written, it takes between T1 + T2 and T1 + 2*T2 before the new clock fre-
quency is active. In this interval, two active clock edges are produced. Here, T1 is the previous clock period, and
T2 is the period corresponding to the new prescaler setting.
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| R5F21274JFP#U0 | 功能描述:MCU FLASH 2K FLASH 16K 32LQFP RoHS:否 類別:集成電路 (IC) >> 嵌入式 - 微控制器， 系列:R8C/2x/27 標(biāo)準(zhǔn)包裝:250 系列:80C 核心處理器:8051 芯體尺寸:8-位 速度:16MHz 連通性:EBI/EMI，I²C，UART/USART 外圍設(shè)備:POR，PWM，WDT 輸入/輸出數(shù):40 程序存儲器容量:- 程序存儲器類型:ROMless EEPROM 大小:- RAM 容量:256 x 8 電壓 - 電源 (Vcc/Vdd):4.5 V ~ 5.5 V 數(shù)據(jù)轉(zhuǎn)換器:A/D 8x10b 振蕩器型:內(nèi)部 工作溫度:-40°C ~ 85°C 封裝/外殼:68-LCC（J 形引線） 包裝:帶卷 (TR) |
| R5F21274JFP#W4 | 制造商:Renesas Electronics Corporation 功能描述:MCU 3/5V - Tape and Reel |
| R5F21274JXXXFP | 制造商:RENESAS 制造商全稱:Renesas Technology Corp 功能描述:SINGLE-CHIP 16-BIT CMOS MCU |
| R5F21274KFP | 制造商:RENESAS 制造商全稱:Renesas Technology Corp 功能描述:RENESAS 16-BIT SINGLE-CHIP MCU R8C FAMILY / R8C/2x SERIES |
| R5F21274KXXXFP | 制造商:RENESAS 制造商全稱:Renesas Technology Corp 功能描述:SINGLE-CHIP 16-BIT CMOS MCU |
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