50 lines
959 B
Markdown
50 lines
959 B
Markdown
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---
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title: 定频
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updated: 2022-01-09 02:57:28Z
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created: 2022-01-08 13:17:43Z
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tags:
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- mcu
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- pll
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- 代码块
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---
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$f_{VCO} = f_{PD} × [PLL\_N + (PLL\_NUM / PLL\_DEN)]$
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其中，$f_{VCO} / f_{PD}$ 得整数部分，$f_{VCO} \% f_{PD}$ 得小数部分， 即$PLL\_NUM / PLL\_DEN$
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与835乘以2^24得小数寄存器值不同
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PLL_DEN取fPD值的2^n（n=0,1,2,3,4）倍可简化运算（小数部分/2^n=PLL_NUM，移位即可，没有额外的除法运算），此时步进
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$f_▲=f_{PD}/PLL\_DEN=1/2^n=1，0.5，0.25，0.125，0.0625 Hz$
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R0 对应
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R36 对应PLL_N
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R37 对应MASH_SEED_EN和PFD_DLY_SEL
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R38 对应PLL_DEN[31:16]，
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R39 对应PLL_DEN[15:0]
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R40 对应MASH_SEED[31:16]，//调节相位用
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R41 对应MASH_SEED[15:0]
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R42 对应PLL_NUM[31:16]，
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R43 对应PLL_NUM[15:0]
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R44 对应A功率调节和A/B输出开关，以及MESH
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R45 对应A输入源和B功率调节
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R46 对应B输入源
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R75 对应DIV，分频数
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#PLL
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#mcu
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#代码块
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