AVR-Chat

--- In AVR-Chat@yahoogroups.com, "Steve Hodge" <steve@...> wrote:
>It would seem to me that all I that needs to happen is that
>I don't use this on-board reset switch when using debugWire.
That is correct.  Applying a reset from other sources while using debugWire will probably cause failure.

One other issue is that you shouldn't have other circuitry that drives the reset line high.  A switch or open collector/drain device should not be a problem.

Don Kinzer
ZBasic Microcontrollers
http://www.zbasic.net

I am designing a circuit to use a Mega328P, which has debugWire.  When not
using debugWire I want to enable RESET and use it as an on-board reset with
a momentary push button switch.  The circuit thus simply consists of a
connection from the RESET pin (pin #1, PC6) on the uC to this switch, with a
10K pull-up to Vcc and the other side of the switch to GND.   The RESET pin
is also connected to the RESET pin of the ISP header.  There are no
capacitors involved.

This seems to satisfy the requirements outlined on p268 of the Mega328P data
sheet, which are (quote):

-- Pull-up resistors on the dW/(RESET) line must not be smaller than 10kΩ.
The pull-up resistor
is not required for debugWIRE functionality.
-- Connecting the RESET pin directly to VCC will not work.
-- Capacitors connected to the RESET pin must be disconnected when using
debugWire.
-- All external reset sources must be disconnected.

However, the last one ("all external reset sources must be disconnected")
confuses me.  Does it mean I have to electrically break the trace to the
push-button switch?  

It would seem to me that all I that needs to happen is that I don't use this
on-board reset switch when using debugWire.   Is that correct?

Steve
 

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Thanks, Don.   Do you mean failure as in smoke?   Steve

From: AVR-Chat@yahoogroups.com [mailto:AVR-Chat@yahoogroups.com] On Behalf
Of DonaldK
Sent: Saturday, November 07, 2009 2:38 PM
To: AVR-Chat@yahoogroups.com
Subject: [AVR-Chat] Re: reset & debugwire circuit

 

  

--- In AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com> , "Steve
Hodge" <steve@...> wrote:
>It would seem to me that all I that needs to happen is that
>I don't use this on-board reset switch when using debugWire.
That is correct. Applying a reset from other sources while using debugWire
will probably cause failure.

One other issue is that you shouldn't have other circuitry that drives the
reset line high. A switch or open collector/drain device should not be a
problem.

Don Kinzer
ZBasic Microcontrollers
http://www.zbasic.net



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