RESET pin strength (m48/88)

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Brutte
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Posted by Brutte: Wed. Jun 8, 2011 - 09:47 PM
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Using AVRs and RESET pin is more complicated than other IOs. I just want you to confirm if I am right about this pin functionality as an IO.

RESET pin on AVRs with RSTDISBL fuse can be (part dependent):

    1) Open drain IO driver (mature tn12) 2) Weak IO driver (tn2313,tn13..)
    3) Regular strength IO driver?

QA: Datasheets of m48/88/168, usb82/162 and other AVRs with RESETDSBL fuse do not mention the difference in between RESET and a regular IO driver strength in "Pin Driver Strength" sections because:

    a) there isn't any difference. b) Atmel forgot to write about this fact, and it is still 2) type weak IO capable of 1mA sink/source?

QB: Is this pin still 12V capable, when RSTDISBL is programmed? What happens when it is on 12VDC and I set IO high?

No RSTDISBL, no fun!

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AVR Microcontrollers, megaAVR and tinyAVR
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Gold Markclawson
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Posted by clawson: Thu. Jun 9, 2011 - 09:00 AM
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QB: Once RSTDISBL is set then the only way to program the chip *is* using HV programming which involves applying +12V to the _RESET pin. As this immediately triggers the core into a "ready to be programmed" mode the CPU is not making instruction fetches and whatever software you may have in the flash is completely irrelevant as the CPU will not be running in the "normal" sense.

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