project of smartcard

[amr_karimm]

hi
i am making aproject of smartcard {whith fun card} and i have problem in supply the card with a clock as you know the card contain(at90s8515) and and must supply with oscillator to generate the clock but the card have only one pin to provid it with the clock so any one know how to do that
i wish any one can help me if one have asolution u can mail me

 

[Asjad]

clock signal

Dear Friend,

I think you are confused, most micros require a crystal which requires
2 pins.

A smart card requires a clock which is generated externally, you
can do this by using a 555 timer (ASTABLE).

You need to find the maximum frequency required
THe maximum voltage swing into the Smart card

 

[falleafd]

No, you can use only 1 pin of osc. osc usually have 2 pinouts. But you can select osc_in to generate oscilation.

 

[amr_karimm]

Dear Friends,

thanks for your replay ,but i use a (a16f876)pic to read frome card can i take the clock frome the (xtal2)pin of it & if i use it i conect it to the card direct or make some modivy to it ???????

 

[Nigel Goodwin]

Dear Friends,

thanks for your replay ,but i use a (a16f876)pic to read frome card can i take the clock frome the (xtal2)pin of it & if i use it i conect it to the card direct or make some modivy to it ???????

It depends on the loading the card causes, you may need to add a buffer to prevent the oscillator being stopped by the extra load.

 

[amr_karimm]

what kind of buffer???????

 

[Asjad]

possible buffer

You could use a LM311 as a buffer

OR

you could use a TTL logic buffer.

These are possible buffers, check with nigel!!!!!

 

[Nigel Goodwin]

what kind of buffer???????

A high input impedance, and a low output impedance - there are many possibilities, including a single transistor, or a logic gate. But for a start, try it without and see if it works.

 

[amr_karimm]

thanks for all friend i will try your advises and will see and by the way any one know a site have aexamples of at90s8515 microcontroler programe write with asm for project

 

[TKS]

buffer

nigel...


if i would use a NPN transistor

with the Collector to 5Volts the Emitter to the clockin line..

and the B to the OSC2Pin..

would that work..???


TKS

when i started testing it worked...connecting it directly..

but after a while and adding some Caps to the circuit..it didn't anymore

i meassure 2volts on the incoming OSC line..

and 1,8 on the 2 line.. offcourse i dunno when it takes the measurement because it will go up and down with the freq of the crystal right??

Regards,

TKS