Martin McCormick wrote:

>Bob Axtell writes:
>  
>
>>Smart cards: do you mean MMC or SD cards? If so several of us have done 
>>those
>>sucessfully with PICs. We use the SPI channel.  
>>    
>>
>
>	Thanks for all the links and other information.
>
>	I think I mean SD.  I am new to the nomenclature but I am
>referring to the credit card sized devices that have a CPU embedded in
>the plastic with 8 gold contacts on one side and human-readable art
>work and information on the other side.
>
>	According to some of the literature I have read VIA google,
>they only actually use 6 of the 8 contacts and clock the CPU at either
>the NTSC color burst frequency of 3.579x MHZ or 4.92 MHZ, both of
>which can be divided down to something close to 9600 baud.
>
The MMC and SD card don't care at what speed they are clocked.  Use a 20Mhz
clock or crystal.


>  The cards
>are described by ISO7816 which describes the mechanical and electrical
>characteristics of the cards.  Of course, when you get to the
>application part of the card, there is lots of variation in software
>and security procedures between one use and another.
>
>	I kind of figured that the ATMEL didn't possess any particular
>magic, but was just the CPU of choice by that particular author.
>
That's about it.


>  It
>sounds like any PIC that has a SPI and 2 other I/O wires free should
>do the job.
>
ditto

>  I would think the crystal frequency should either be
>3.57x*4 or 4.92*4 so that the clock out on the PIC could be the clock
>in on the card.  I haven't gotten this far yet, but it may even be
>that the cards built around a 4.92 MHZ clock can run at 3.58 MHZ if
>you can set the SPI deviser to 512 instead of 372.
>
Clock speed doesn't matter. Really.

>  The serial data
>will be at 6992 or so baud, but the SPI should follow it just like it
>follows the 9600 baud signal.  It would only really matter if you were
>directly feeding the data to something else like a P.C.
>
>  
>
Good luck!

>	Again thanks to all for more information.
>
>Martin McCormick WB5AGZ  Stillwater, OK 
>OSU Information Technology Division Network Operations Group
>  
>


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