Hi. I have met a really weird programming problem.
After being put away for a year or two, I got my old Ethernut board out in the daylight again. It has a Mega128 with a 14,something MHz crystal.
I hook it up to the ISP cable on my STK500 board, in order to program it, but it doesn't work. It won't work until I reduce the ISP programming clock to 4 kHz (yes, I mean kilo, not mega), but then it works fine. But it is slower than a snail that way.
The processor runs at 14,something MHz, as the serial port transmits at the programmed 115200 baud.
If I use my JTAG, I can program it at full speed without any problems, but I would prefer to use the STK500, as I need the JTAG to debug another AVR that will be connected to this one.
Any ideas? What can make a Mega128 refuse programming at higher speeds than 4 kHz, when it is running at 14 MHz?