参数资料
型号: XE8805AMI028LF
厂商: Semtech
文件页数: 97/156页
文件大小: 0K
描述: IC DAS 16BIT FLASH 8K MTP 64LQFP
标准包装: 160
系列: XE880x
应用: 感测机
核心处理器: Coolrisc816?
程序存储器类型: 闪存(22 kB)
控制器系列: XE8000
RAM 容量: 512 x 8
接口: UART,USRT
输入/输出数: 24
电源电压: 2.4 V ~ 5.5 V
工作温度: -40°C ~ 85°C
安装类型: 表面贴装
封装/外壳: 64-LQFP
包装: 托盘
供应商设备封装: 64-LQFP(10x10)
产品目录页面: 585 (CN2011-ZH PDF)
配用: XE8000MP-ND - PROG BOARD AND PROSTART2 CARD
Semtech 2006
www.semtech.com
7-4
XE8805/05A
7.5
Clock sources
7.5.1
RC oscillator
7.5.1.1
Configuration
The RC oscillator is always turned on and selected for CPU and system operation at power-on reset and when
exiting sleep mode. It can be turned off after the Xtal (quartz oscillator) has been started, after selection of the
external clock or by entering sleep mode.
The RC oscillator has two frequency ranges: sub-MHz (100 kHz to 1 MHz) and above-MHz (1 MHz to 10 MHz).
Inside a range, the frequency can be tuned by software for coarse and fine adjustment. See registers
RegSysRcTrim1 and RegSysRcTrim2.
Bit EnableRC in register RegSysClock controls the propagation of the RC clock signal and the operation of the
oscillator. The user can stop the RC oscillator by resetting the bit EnableRC. Entering the sleep mode disables the
RC oscillator.
Note: Before turning off the RC oscillator, the cpusel bit in RegSysClock must be set to one.
Note: The RC oscillator bias can be maintained while the oscillator is switched off by setting the bit BiasRc in
RegSysClock. This allows a faster restart of the RC oscillator at the cost of increased power consumption when
the oscillator is disabled (see section 7.5.1.3).
7.5.1.2
RC oscillator frequency tuning
The RC oscillator frequency can be set using the bits in the RegSysRcTrim1 and RegSysRcTrim2 registers.
Figure 7-2 shows the nominal frequency of the RC oscillator as a function of these bits. The absolute value of the
frequency for a given register content may change by
±50% from chip to chip due to the tolerances on the
integrated capacitors and resistors. However, the modification of the frequency as a function of a modification of
the register content is fairly precise for frequencies below 2MHz. This means that the curves in Figure 7-2 can shift
up and down but that the slope remains unchanged.
The bit RcFreqRange modifies the oscillator frequency by a factor of 10. The upper curve in the figure
corresponds to RcFreqRange=1.
The RcFreqCoarse modifies the frequency of the oscillator by a factor (RcFreqCoarse+1). The figure represents
the frequency for 5 different values of the bits RcFreqCoarse: for each value the frequency is multiplied by 2.
Incrementing the RcFreqFine code increases the frequency by about 1.4%.
The frequency of the oscillator is therefor given by:
fRC=fRcmin(1+9RcFreqRange)(1+RcFreqCoarse)(1.014)
RcFreqFine
with fRcmin the RC oscillator frequency if the registers are all 0. At higher frequencies, the frequency may deviate
from the value predicted by the equation.
Not
Recommended
for
New
Designs
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