>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>Sent: 20 February 2006 09:14
>To: Microcontroller discussion list - Public.
>Subject: RE: [PIC] 2 questions about 18f4550
>
>
>
>
>> -----Original Message-----
>> From: piclist-bounces@mit.edu
>> [mailto:piclist-bounces@mit.edu] On Behalf Of Bob Axtell
>> Sent: Monday, February 20, 2006 9:31 AM
>> To: Microcontroller discussion list - Public.
>> Subject: Re: [PIC] 2 questions about 18f4550
>>
>> Assume for the moment that your PIC design has a credit card reader
>> attached at your PIC's pin RB0. The card reader is an output. 
>> If the PIC powered up as an  output as well, either the PIC is 
>> damaged by the credit card reader, or the  credit card 
>> reader is damaged by the PIC. MAYBE they won't be damaged... 
>> but we engineers don't tolerate things like that, it is not good 
>> practice to hope things aren't broken by just powering them up.
>> 
>
>To prevent power-up wrong behaviors is actually an important
>considerations for production quality designs.
>
>I understand your points but I think you have a wrong assumptions 
>here. You should not attached the credit card reader directly to 
>your PIC's pin RB0. That will for sure fail the ESD test. There 
>should be some circuits between them.

The credit card reader was just an example, it could have been a push button, a serial driver (MAX232 etc.), or many other devices that could cause a conflict if the PIC pins were configured to outputs at power up.

Regards

Mike

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