Hi all,

I thought I'd try out the Scenix SX chips, (since they seem able to do
everything a 16F84 can, but much faster :), but don't really want to
spend $300 on the SX-Key programmer. So, I thought I'd have a shot at
building my own. Since the SX chips I've ordered won't be here for a few
days, I'm trying to get as much of the programmer built as I can in the
meantime. I'm using a PIC 16F84 as an interface between the PC and SX.

I've written the PIC code that will talk to the SX, and in order to test
it, I've hacked together some PIC code that emulates a Scenix chip in
ISP mode (128KHz timing signal, bidirectional data transfer, etc...)
based on the Device Programming guide from www.scenix.com. So far, the
two PICS talk to each other quite happily, so if the Scenix docs are to
be believed, this part should work fine.

Now, according to the Scenix docs, in order to get the SX into ISP mode,
you have to drive OSC2 low, toggle OSC1 9 times (presumably at 5V),
release OSC2, then raise OSC1 to 12.5V. This needs to be controlled by
the PIC.

I have a 12V supply, a 7805, and a 7812. It would appear that I need to
be able to place the SX's OSC1 line at 0V, 5V and 12.5V, all under
control of the PIC - and since I'm a programmer by trade, not an
engineer, I have absolutely no idea how to proceed!

If anyone has suggestions, I'd be grateful. Alternatively, if anyone's
built a cheap scenix programmer, and released the schematics (couldn't
find any on the web), that'd be cool too.

Cheers,

Ben