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Question on reset supervisor for DM6437

Anonymous
Anonymous

Hi All,

 

I would like to ask one question on reset supervisor’s configuration for DM6437.

 

 

 

 

In EVM6437 schematics sheet 33 – Reset Supervisor,  what is the purpose of the diode D10? Since D10 pass only higher voltage of its pin 1 respective to 3, then when U57 is asserts low, the low voltage signal cannot be passed to U56’s MRn pin, which renders the cascading ineffective.

 

So why D10 is still placed here? Can I remove it?

 

 

Another question is on EMU_SYS_RESETn signal. Its receiving end is pin PONRSn of EVM6437’s emulation USB which is proprietary to SpectrumDigital, so I have no idea of its internal operation. But from the schematics it seems that EMU_SYS_RESETn and RESETn probably related in that the former triggers the later, is it the case?

 

 

 

 

 

Thanks,

Zheng

  • 0
    Genius 3575 points

    I didn't design the board, so take this with a grain of salt, but D10 is probably used to isolate the emu_sys_resetn line from the sys_resetn line.  This allows the emulator logic to be reset without resetting all the other circuits on the board.  If U57 pulls its reset output low, the diode will block current from pulling down the MR/ line on U56.  On the flip side, if the user engages the switch, the diode will be forward biased, so BOTH reset lines will be pulled low.

    So no, don't remove it.  A good rule of thumb to follow is that if you don't understand a circuit, don't mess with it.   And resetn will trigger emu_sys_resetn, NOT the other way around as you have suggested.

    I'd also like to politely suggest that you begin referring questions about circuit design and layout on the evmdm6437 board directly to spectrum digital, or find a general electronics forum elsewhere online to post them.  You are flooding a DSP specific forum with general electronics questions that make it difficult for others to find the answers that they need.

  • Anonymous
    0 Anonymous in reply to MattLipsey

    Dear Matt,

    I still haven't got the question why D10 is used. If when the switch is not engaged D10 is cutoff, then when U57 or U58 (through U57) detects a low voltage, how can it be relayed to U56 and consequently reset the DSP?

    Thanks for reminding. I will try asking on other relevant forums as much as possible.

     

    Zheng