Manfred,

"but the newer 89S52 is ISP-useable (no prommer nessesary) and has a watchdog."

Is the watchdog disabled, or if enabled, are you petting it?

I was quite baffled by a Cygnal part last week; it just wouldn't work, but the "Blinky" demo that came with the eval/JTAG board did. So I ran my program in the debugger, and it seemed to reset itself. Hmmm! So I RTFDS and realized that the watchdog is enabled by default. So, I disabled it and now things are much better.

-a