TOP

FAQ

    • .How to select parameters to get 4MHz RC oscillator frequency at VDD = 5V power supply?

      When use external RC oscillator circuit to obtain system clock, It is suggested as follows:
      ◆ It is suggested to use 33pf capacitor as RC oscillation capacitor, for 1 ~ 8MHz frequency, please refer to the following table (VDD=5V):

      frequency resistance capacitance
      8 MHz 1800Ω 33pf
      4 MHz 3900Ω 33pf
      2 MHz 8200Ω 33pf
      1 MHz 18000Ω 33pf

      ◆ RC oscillator clock configurations are as follows:

      ◆ It is proposed to add a 47uf capacitor to MCU power side, which can effectively improve the system stability and isolate noise outside and protect system works well.
      ※ Note: The above parameters are for reference only, there is a deviation in actual RC oscillation frequency due to resistance and capacitance accuracy of different parameters, For actual frequency please measured it.

    • .What is the meaning for "1T" mentioned in SONIX MCU specifications?

      The meaning of "1T" is MCU maximum operation clock speed, that is Fcpu = Fosc, because the vast majority of SONIX MCU instructions are single clock cycle, so the system executes an instruction for a minimum time of oscillations. Currently, SN8P2XXX series chips most support "1T", however, in some cases, or some chips can not reach "1T", such as when selecting Noise_Filter Enable in Code Option, the top speed for MCU running clock is only Fcpu = Fosc/4, which is "4T", no matter under what conditions, SN8P2614 can only run the fastest "4T".

    • .What is the state for Xout pin in the external RC oscillator mode?

      In external RC mode, the oscillation signal is input to MCU internal through Xin, at this time, the state of Xout pin can be noted as the following two points:
      1. When pin name is Xout/Fcpu, such as SN8P2700 series, Xout pin output Fcpu, and can not be used as general I/O port.
      2. When pin name is Xout/Px.x, such as SN8P2500 series, Xout pin will automatically be released for general I/O port, the state can be set by the program, it can not output Fcpu or Fosc.

    • .System board using RC oscillator, how to solve the simulation and real chip operating frequency error problem?

      It is proposed to use crystal when simulation, the actual chip with RC oscillator circuit way to develop.

      First of all, calculate external crystal and RC oscillator parameters according to chip operating frequency, plug crystal into emulator, re-compiler the program when simulation process passed, modify High_Clk option to RC, after the chip be programmed, adjust RC oscillator component parameters on target board until it meets the requirements.

      In order to adjust RC component parameters conveniently, you can use an idle I/O port to output a fixed frequency square wave, so use the oscilloscope waveform to adjust RC parameters, and also facilitate the production of debugging. If no idle I/O port can be used, you can write a simple test program, program chips to adjust.

    • .What issues should be paid attention to when using RC oscillator?

      RC oscillation frequency is mainly influenced by the following conditions:

      1.RC oscillator voltage, different voltage will affect RC oscillator frequency. when in high operating frequency, users should pay attention to the system operating voltage, if operating voltage is too low, the system will possibly work in unstable state, especially for battery-powered systems;

      2.Operating ambient temperature, different temperature will also affect the RC oscillator frequency;

      3.External interference sources, different RC combinations will have different noise filter performance, PCB layout can also improve the stability of RC oscillation, Capacitor (C) should be connected to MCU ground and should not be directly connected to external circuit.

    • .Can target board provide system clock?

      No, it can't, internal crystal oscillator of emulator is the default crystal in simulation, target board crystal does not work.

    • .What is the internal ILRC frequency?

      Operating voltage influence internal oscillator frequency ILRC greatly, when VDD = 5V, about 32KHz, when VDD = 3V, about 16KHz.

    • .When you want a higher rate of program frequency(Fcpu to 16M or 8M) and real system would work in complex situations more serious flood and disturbance, whether enable Noise_Filter will give a great i

      When users system works in high noise environment, it is suggested to open noise filter function, that is, to Enable Noise_Filter, in this way, it can filter noise or reduce the interference caused by the external environment.
      In Sonix MCU, it is announced that, when enabled Noise_Filter in Code Option, Fcpu option will automatically mask out Fosc/1 and Fosc/2. So even if you plug 16M crystal, if Noise_Filter enabled, Fcpu can only run 4M in largest.
      In view of the above two points, the user should consider all aspects and to minimize the execution rate as slow as possible. If the program does require a higher implementation rate, you can consider other ways to reduce the interference, such as adding a filter capacitor.

    Support