msp430的小问题紧急求助

只看该作者 · 2012-3-19 17:51

RSEL2~RSEL0:选择某个内部电阻以决定标称频率（0最低，7最高）
1什么叫其标称频率？
2最低是多少？最高多少？
3设置不同的标称频率对单片机工作什么影响？
4一般怎么设置？如果不设置默认是多少？
对于DCOCTL
1.DCO0~DCO2:DCO Select Bit,定义了8种频率之一，而频率由注入直流发生器的电流定义
2 MOD0~MOD4:Modulation Bit,频率的微调
3，我该怎么理解？怎么设置？不设置默认是多少呢？

对于BCSCTL3=XCAP_3; // 内部电容，12.5PFCS
头文件中还有0 ，6 ， 10PF 三者有什么不同？

只看该作者 · 2012-3-20 17:59

顶一下

只看该作者 · 2012-3-21 17:32

最小在80k左右,最高在8M左右,如果用外部电阻的话就得根据阻值来了,反正都是不咋准的
这些问题手册上都有
After a PUC, the internal resistor is selected for the DC generator, RSELx =
4, and DCOx = 3, allowing the DCO to start at a mid-range frequency. MCLK
and SMCLK are sourced from DCOCLK. Because the CPU executes code
from MCLK, which is sourced from the fast-starting DCO, code execution
begins from PUC in less than 6  µs. The typical DCOx and RSELx ranges and
steps are shown in Figure 4−5.
The frequency of DCOCLK is set by the following functions:
The current injected into the DC  generator by either the  internal or  external
resistor defines the fundamental frequency. The DCOR bit selects the
internal or external resistor.
The three RSELx bits select one of eight nominal frequency ranges for the
DCO. These ranges are defined for an individual device in the
device-specific data sheet.
The three DCOx bits divide the DCO range selected by the RSELx bits into
8 frequency steps, separated by approximately 10%.
The five MODx bits, switch between the frequency selected by the DCOx
bits and the next higher frequency set by DCOx+1.  When DCOx = 07h,
the MODx bits have no effect because the DCO is already at the highest
setting for the selected RSELx range.

msp430的小问题紧急求助

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