Wizard Of Oz wrote:
bluebird wrote:This may not be the answer you are looking for. Back in the 80's I had a card called a "Thunderclock". Actually it was a clone of that device. It could generate an interrupt every millisecond. Of course on a ][+ there isn't a lot you can do with that small of an interval. The //e clone I had later allowed a little more to be done but still...I want to use timer interrupt in Apple II/Apple II+/Apple IIe. For example, I want to install 300ms timer interrupt and want its ISR called periodically. Is there any example?The circuit was fairly simple. Using modern technology someone could probably put all the functionality (plus a bunch more) on a single chip. Maybe the people making hardware would consider adding a clock to their product if there isn't one there already. Of course I wonder how the system would handle multiple clocks...
As David noted, any card containing a 6522 VIA with a connected IRQ line could generate almost any interrupt interval. The Mockingboard is one (relatively) common card that can do this. -michael NadaNet and AppleCrate II: parallel computing for Apple II computers! Home page: http://home.comcast.net/~mjmahon "The wastebasket is our most important design tool--and it's seriously underused."