How do i clear the "err" on my Stereo in my 1990 Mazda miata?

I bought a 1990 mazda miata and the stereo has a security system . Right now there is blinking "err" and the stereo is not usable.I know there is a way to clear it ut can't find the directions. Anyone have the out there?How do i clear the "err" on my Stereo in my 1990 Mazda miata?
Should be an indented factory reset button, however if there is one it'll probably reset all radio channels etc, had the same problem last month with my kenwood stereo but fine after resetHow do i clear the "err" on my Stereo in my 1990 Mazda miata?
Try this link: http://www.miata.net/faq/faq3.html#L