收藏本站
Low-, medium- and high-density reset and clock control (RCC)
RM0008
If the USB interface is used in the application, the PLL must be programmed to output 48 or
72 MHz. This is needed to provide a 48 MHz USBCLK.
6.2.4
6.2.5
Note:
80/995
LSE clock
The LSE crystal is a 32.768 kHz Low Speed External crystal or ceramic resonator. It has the
advantage providing a low-power but highly accurate clock source to the real-time clock
peripheral (RTC) for clock/calendar or other timing functions.
The LSE crystal is switched on and off using the LSEON bit in Backup domain control
register (RCC_BDCR) .
The LSERDY flag in the Backup domain control register (RCC_BDCR) indicates if the LSE
crystal is stable or not. At startup, the LSE crystal output clock signal is not released until
this bit is set by hardware. An interrupt can be generated if enabled in the Clock interrupt
register (RCC_CIR) .
External source (LSE bypass)
In this mode, an external clock source must be provided. It must have a frequency of
32.768 kHz. You select this mode by setting the LSEBYP and LSEON bits in the Backup
domain control register (RCC_BDCR) . The external clock signal (square, sinus or triangle)
with ~50% duty cycle has to drive the OSC32_IN pin while the OSC32_OUT pin should be
left Hi-Z. See Figure 9 .
LSI clock
The LSI RC acts as an low-power clock source that can be kept running in Stop and
Standby mode for the independent watchdog (IWDG) and Auto-wakeup unit (AWU). The
clock frequency is around 40 kHz (between 30 kHz and 60 kHz). For more details, refer to
the electrical characteristics section of the datasheets.
The LSI RC can be switched on and off using the LSION bit in the Control/status register
(RCC_CSR) .
The LSIRDY flag in the Control/status register (RCC_CSR) indicates if the low-speed
internal oscillator is stable or not. At startup, the clock is not released until this bit is set by
hardware. An interrupt can be generated if enabled in the Clock interrupt register
(RCC_CIR) .
LSI calibration is only available on high-density and connectivity line devices.
LSI calibration
The frequency dispersion of the Low Speed Internal RC (LSI) oscillator can be calibrated to
have accurate RTC time base and/or IWDG timeout (when LSI is used as clock source for
these peripherals) with an acceptable accuracy.
This calibration is performed by measuring the LSI clock frequency with respect to TIM5
input clock (TIM5CLK). According to this measurement done at the precision of the HSE
oscillator, the software can adjust the programmable 20-bit prescaler of the RTC to get an
accurate time base or can compute accurate IWDG timeout.
Doc ID 13902 Rev 9
发布紧急采购，3分钟左右您将得到回复。

采购需求

(若只采购一条型号，填写一行即可)

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

发布成功！您可以继续发布采购。也可以进入我的后台，查看报价

*型号 *数量 厂商 批号 封装
添加更多采购

我的联系方式

*
*
*
相关PDF资料
MCBTMPM330 BOARD EVAL TOSHIBA TMPM330 SER
MCIMX25WPDKJ KIT DEVELOPMENT WINCE IMX25
MCIMX53-START-R KIT DEVELOPMENT I.MX53
MCM69C432TQ20 IC CAM 1MB 50MHZ 100LQFP
MCP1401T-E/OT IC MOSFET DRVR INV 500MA SOT23-5
MCP1403T-E/MF IC MOSFET DRIVER 4.5A DUAL 8DFN
MCP1406-E/SN IC MOSFET DVR 6A 8SOIC
MCP14628T-E/MF IC MOSFET DVR 2A SYNC BUCK 8-DFN
相关代理商/技术参数
MCBSTM32EXLU 功能描述:开发板和工具包 - ARM EVAL BOARD + ULINK2 FOR STM32F103ZG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32EXLU-ED 制造商:ARM Ltd 功能描述:KEIL STM STM32EXL EVAL BOARD
MCBSTM32EXLUME 功能描述:开发板和工具包 - ARM EVAL BOARD + ULINKME FOR STM32F103ZG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F207IG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200U 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F207IG + ULINK2 RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200UME 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F207IG ULINK-ME RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V
MCBSTM32F200UME-ED 制造商:ARM Ltd 功能描述:KEIL STM32F207IG EVAL BOARD
MCBSTM32F400 功能描述:开发板和工具包 - ARM EVAL BOARD FOR STM STM32F407IG RoHS:否 制造商:Arduino 产品:Development Boards 工具用于评估:ATSAM3X8EA-AU 核心:ARM Cortex M3 接口类型:DAC, ICSP, JTAG, UART, USB 工作电源电压:3.3 V