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    參數(shù)資料
    型號(hào): 56F802
    廠商: 飛思卡爾半導(dǎo)體(中國(guó))有限公司
    英文描述: 16-bit Digital Signal Controllers
    中文描述: 16位數(shù)字信號(hào)控制器
    文件頁(yè)數(shù): 23/40頁(yè)
    文件大?。?/td> 2472K
    代理商: 56F802
    Clock Operation
    56F802 Technical Data, Rev. 7
    Freescale Semiconductor
    23
    3.5 Clock Operation
    The 56F802 device clock is derived from an on-chip relaxation oscillator. The internal PLL generates a
    master reference frequency that determines the speed at which chip operations occur.
    The PRECS bit in the PLLCR (phase-locked loop control register) word (bit 2) must be set to 0 for internal
    oscillator use.
    3.5.1
    The 56F802 internal relaxation oscillator provides the chip clock without the need for an external crystal
    or ceramic resonator. The frequency output of this internal oscillator can be corrected by adjusting the 8-bit
    IOSCTL (internal oscillator control) register. Each bit added or deleted changes the output frequency of
    the oscillator allowing incremental adjustment until the desired frequency is achieved. Figures 9 and 10
    show the typical characteristics of the 56F802 relaxation oscillator with respect to temperature and trim
    value.
    Use of On-Chip Relaxation Oscillator
    During factory production test, an oscillator calibration procedure is executed which determines an
    optimum trim value for a given device (8MHz at 25
    o
    C). This optimum trim value is then stored at address
    $103F in the Data Flash Information Block and recalled during a trim routine in the boot sequence
    (executed after power-up and RESET). This trim routine automatically sets the oscillator frequency by
    programming the IOSCTL register with the optimum trim value.
    Due to the inherent frequency tolerances required for SCI communication, changing the factory-trimmed
    oscillator frequency is not recommended. If modification of the Boot Flash contents are required, code
    must be included which retrieves the optimum trim value (from address $103F in the Data Flash
    Information Block) and writes it to the IOSCTL register. Note that the IFREN bit in the Data Flash control
    register must be set in order to read the Data Flash Information Block.
    Table 3-8 Relaxation Oscillator Characteristics
    Operating Conditions:
    V
    SS
    = V
    SSA
    = 0 V, V
    DD
    = V
    DDA
    = 3.0–3.6 V, T
    A
    = –40
    °
    to +85
    °
    C
    Characteristic
    Symbol
    Min
    Typ
    Max
    Unit
    Frequency Accuracy
    1
    1.
    Over full temperature range.
    f
    +2
    +5
    %
    Frequency Drift over Temp
    f/
    t
    +0.1
    %/
    o
    C
    Frequency Drift over Supply
    f/
    V
    0.1
    %/V
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    相關(guān)代理商/技術(shù)參數(shù)
    參數(shù)描述
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