On Wed, 21 Jul 1999 15:19:39 -0400 Amr Ahmed writes: >Hi, > >Please do anyone have a test code with simple circuit >for pic16f84 20mhz ? I've tested several 10 MHz ones and found they won't work at 20 MHz. About 16 MHz was the limit. You may need to buy a lot of 16F84's to find one that will work at 20 MHz. You may get one the first time, or you may never find one. You are slightly more likely to find one if you buy -10 chips, because at least that'll weed out the ones that won't work even at 10 MHz. But if Microchip was making 16F84's that work reliably at 20 MHz, they would spec them that way. It's been widely concluded that the 4 MHz and 10 MHz versions are the same chip. The only difference is the testing and the label. If they are having a "bad PIC day" at the factory and the PICs start failing the 10 MHz test, they can sell them as 4 MHz units. On the other hand, if they have a lot of -10 ones in stock, they may not bother to test any beyond 4 MHz. So the -4 ones from that day may work just fine at 10 MHz or beyond, but not even Microchip could tell you for sure. In summary the slightly lower price of a -4 chip is because it isn't guaranteed to work at 10 MHz. ___________________________________________________________________ Get the Internet just the way you want it. Free software, free e-mail, and free Internet access for a month! Try Juno Web: http://dl.www.juno.com/dynoget/tagj.