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Propeller and Pullup resistors? — Parallax Forums

Propeller and Pullup resistors?

Brian CarpenterBrian Carpenter Posts: 728
edited 2007-03-28 07:48 in Propeller 1
Does the Propeller have built in pullup resistors like in the SX chips.· I use the pullups in the sx to avoid these extra components on the board.· Are they present in the Propeller?

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Comments

  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2007-03-28 07:32
    Yes, they are called P-channel MOSFETs smilewinkgrin.gif

    Seriously though, NO (as far as I know). Pull-ups can be useful but unless they are implemented well they can be a nuisance. If they are non-programmable pull-ups then you lose the high-impedance input that is necessary at times plus it is harder to make the device really low-power as any inputs could be drawing current. If they are programmable then where do you stop as you can have several registers dedicated to this function alone and there will still be users who will be unhappy about how it is implemented.

    Have you heard about USERs? They are a special device that is a User Selectable External Resistor roll.gif

    *Peter*
  • T ChapT Chap Posts: 4,223
    edited 2007-03-28 07:38
    In looking at the RESn pin, it sure looks like it is floating in all the schematics. I thought it was pulled up since the NPN isn't really contributing any high to keep it there.
  • Peter JakackiPeter Jakacki Posts: 10,193
    edited 2007-03-28 07:48
    If BOE is low then the RES pin is also an input/output with a pullup of about 5K otherwise RES is a normal high-impedance CMOS input with Schmitt Trigger.

    *Peter*
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