SIM Card Detect query

Hi all,

With regard to SIM card interfacing, does anyone know if the CD pins are normally active low or active high (as in, when you insert the card should the CD line be connected high or low).

I've tried googling and checking the datasheet for the GSM Modem I'm using but it's not clear at all.

I can try it both ways obviously, but if someone here knows the answer then it means I can set it correctly first time on my prototype board! Cheers!

Brian H

Are you sure you're talking about a sim card interface? Sim cards don't have a dedicated CD line.

A lot of SIM card holder have a SIM detect switch. I've never used it as the phone modules I've used don't seem to need it.

Yes, SIM card holders commonly have a detect switch (the card simply shorts the contacts) - but many GSM modules don't use that connection anyway.