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AM1808 GPIO翻转速度问题

Andy Xie
Prodigy 20 points
Other Parts Discussed in Thread: AM1808

最近在使用AM1808做一个项目，打算使用GPIO模拟一个CLK信号输出，不知道AM1808的GPIO翻转速度最大是多少？能否模拟输出一个8MHz的CLK信号输出？希望有了解这一块的大神指点一二，感谢！

  • 0
    TI__Mastermind 19320 points

    够呛 

    而且没有实时性，你CPU如果跑别的任务，这速度会有很大变化

    建议用PWM模块来做

  • 0 回复 Denny%20Yang99373
    Prodigy 20 points

    这个芯片的PWM最大可以做到多少MHz的频率？目前还没有仔细看datasheet。

  • 0
    TI__Mastermind 21947 points

    PWM参数

    Table 6-127 Switching Characteristics Over Recommended Operating Conditions for eHRPWM

    PARAMETERTEST 
    CONDITIONS    		1.3V, 1.2V1.1V1.0VUNIT
    MINMAXMINMAXMINMAX
    tw(PWM) Pulse duration, 
    PWMx output high/low    		 20 20 26.6 ns
    tw(SYNCOUT) Sync output 
    pulse width    		 8tc(SCO) 8tc(SCO) 8tc(SCO) cycles
    td(PWM)TZA Delay time, trip input 
    active to PWM forced high
    Delay time,
    trip input active to PWM forced low    		 no pin load; no additional programmable delay 25 25 25 ns
    td(TZ-PWM)HZ Delay time,
    trip input active to PWM Hi-Z    		 no additional programmable delay 20 20 20 ns

    或者timer

    6.30.1 Timer Electrical Data/Timing

    Table 6-130 Timing Requirements for Timer Input(1)(2) (see Figure 6-80)

    NO.1.3V, 1.2V, 1.1V, 1.0VUNIT
    MINMAX
    1 tc(TM64Px_IN12) Cycle time, TM64Px_IN12 4P ns
    2 tw(TINPH) Pulse duration, TM64Px_IN12 high 0.45C 0.55C ns
    3 tw(TINPL) Pulse duration, TM64Px_IN12 low 0.45C 0.55C ns
    4 tt(TM64Px_IN12) Transition time, TM64Px_IN12 0.05C or 10(3) ns
    (1) P = OSCIN cycle time in ns.
    (2) C = TM64P0_IN12 cycle time in ns. For example, when TM64Px_IN12 frequency is 27 MHz, use C = 37.037 ns
    (3) Whichever is smaller. P = the period of the applied signal. Maintaining transition times as fast as possible is recommended to improve noise immunity on input signals.