Jeroni Paul wrote:

I have a Kaon satellite/terrestrial decoder that while starting up it
will reboot several times until it works. After a lot of checking and
testing it seems the front panel micro AT89S52 sometimes won't wait
long enough for all the hardware to initialize. Precise measurements
on the communications between this micro and the main video decoder
reveal that the hardware initializes always at the same speed and it
is the AT89S52 micro that sometimes waits longer and thus starts
successfully but sometimes aborts too early. I don't know what else to
check: supply 5V to the micro perfectly clean, even added capacitors
to check, clock clean (has its own 12MHz crystal). Don't know what
else to check, I can only conclude the micro is faulty. Unfortunately
I don't have the code that runs inside so I don't know if that delay
is implemented by a loop or a hardware timer.
Any ideas?
Look on the board that has the micro for some electro caps. I work with
those types of CPU's and what I have done for a synchronized start up
is to employ a delay circuit for the CPU, a sort of power management
process. Check the caps to make all are up to snuff.. A low valued
cap is going the allow the CPU to start sooner in the power management
section. If this is a new problem, either the main unit is taking too
long, indicating a hardware problem or you do have something strange
going on. You may want to check for bad caps and solder joints, a very
common problem. Especially with today's Lead Free solders.


Jamie