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C8051F91x/90x
11. When the missing clock detector is enabled, why does the MCU reset if I switch from the default
system clock (Low Power Oscillator divided by 8) to smaRTClock divided by 1?
Background:
—The missing clock detector will trigger a reset if the system clock period exceeds 100 μs.
—Switchover between clock sources occurs in 1 clock cycle of the slowest clock.
—Changing the clock divide value requires up to 128 cycles of the undivided clock source.
Since the clock source change occurs in a single cycle and the clock divide change can take up to 128
cycles, the system clock will be set to the new clock source divided by the old divide value for a brief
period of time. In this example, the actual system clock will be 4.096 kHz for up to 128 cycles of the
undivided clock source. This causes the missing clock detector to time out and reset the MCU.
The proper way of changing the system clock when both the clock source and the clock divide value are
being changed is as follows:
If switching from a fast “undivided” clock to a slower “undivided” clock:
a. Change the clock divide value.
b. Poll for CLKRDY > 1.
c. Change the clock source .
If switching from a fast “undivided” clock to a slower “undivided” clock:
d. Change the clock source .
e. Change the clock divide value.
f. Poll for CLKRDY > 1.
12. Why is the MCU pre-maturely released from reset when using a wall supply with a slow rise time?
The maximum VDD Ramp Time is specified at 3 ms. If the power supply ramp takes longer than 3 ms to
reach 0.9 V, then the device may be released from reset before the supply has reached the minimum
operating voltage. The slow ramp time (>3 ms) can occur when using a bench power supply that does not
have an output enable switch.
Rev. 0.2
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相关PDF资料
C8051F930-TB
BOARD TARGET/PROTO W/C8051F930
C8051T610DB24
DAUGHTER BOARD T610 24QFN SOCKET
C8051T630DB20
BOARD SOCKET DAUGHTER 20-QFN
CAN-100
BOARD EVAL RS232 100QFP
CANADAPT28
KIT ADAPTER CANDEMOBOARD 28PLCC
CAT24AA01WI-GT3
IC EEPROM SERIAL 1KB I2C 8SOIC
CAT24AA02WI-G
IC EEPROM SERIAL 2KB I2C 8SOIC
CAT24C01ZI-G
IC EEPROM SERIAL 1KB I2C 8MSOP
相关代理商/技术参数
C8051F912-GDI
功能描述:8位微控制器 -MCU 16kB Flash MCU RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
C8051F912-GM
功能描述:8位微控制器 -MCU 16KB 12ADC 24QFN
RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
C8051F912-GMR
功能描述:8位微控制器 -MCU 16KB 12ADC RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
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功能描述:8位微控制器 -MCU 16KB 12ADC 24QSOP
RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
C8051F912-GUR
功能描述:8位微控制器 -MCU 16KB 12ADC RoHS:否 制造商:Silicon Labs 核心:8051 处理器系列:C8051F39x 数据总线宽度:8 bit 最大时钟频率:50 MHz 程序存储器大小:16 KB 数据 RAM 大小:1 KB 片上 ADC:Yes 工作电源电压:1.8 V to 3.6 V 工作温度范围:- 40 C to + 105 C 封装 / 箱体:QFN-20 安装风格:SMD/SMT
C8051F912-TB
功能描述:开发板和工具包 - 8051 Prototyping Board w/C8051F930
RoHS:否 制造商:Silicon Labs 产品:Development Kits 工具用于评估:C8051F960, Si7005 核心: 接口类型:USB 工作电源电压:
C8051F920
制造商:SILABS 制造商全称:SILABS 功能描述:25 MIPS, 8 kB Flash, Ultra Low Power, Capacitive Sensing MCU
C8051F920-F-GM
制造商:Silicon Laboratories Inc 功能描述:32KB,10ADC,32PIN MCU - Rail/Tube 制造商:Silicon Laboratories Inc 功能描述:MCU 32KB FLASH 10BIT ADC 32QFN