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Recommendation for reset IC in Propeller project — Parallax Forums

Recommendation for reset IC in Propeller project

agsags Posts: 386
edited 2011-08-30 21:05 in General Discussion
I'm designing a board usign the P8X and the WizNET module. I'm running out of I/O pins. Up until now, I've dedicated a Prop I/O pin to reset other components (the WizNET module, registers, etc) at startup. I'd like to reclaim that I/O pin for use in other areas. I've read that without Schmitt trigger input, a simple RC circuit won't likely work. I've searched and see there are a plethora of options (too many to search through). I was wondering if there is a standard way of doing this that is used by people on this forum. One additional complication is that I have both 3.3v and 5v chips that will need to be reset on power up. Luckily, they both have RESn (low reset). Thanks for any suggestions/tips from your experience.

Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-30 17:49
    Firs of all, will the 5V chips run with their /RST pins held at 3.3V?

    -Phil
  • agsags Posts: 386
    edited 2011-08-30 20:57
    Phil Pilgrim (PhiPi) wrote: »
    Firs of all, will the 5V chips run with their /RST pins held at 3.3V?

    -Phil

    Yes, my apologies, I should have made that clear. I'm using a 74HCT595 part; V(ih) min=2.0v, so 3.3v in to the /RES pin will take the part out of reset state. The WizNet module runs on 3.3v supply so it's also OK.
  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2011-08-30 21:05
    If you enable brownout reset on the Propeller, the /RES pin gets pulled low during power-up. It might be able to sink enough current to reset those other two chips. 'Maybe worth a try!

    -Phil
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