Help -- 12C509A Won't Start
Spehro Pefhany email (remove spam text)
At 02:21 AM 4/5/01 -0700, you wrote:
>I've got a circuit using the 12C509A (JW part) with all pins as pure
>I/O, i.e. using Internal RC, no WDT, no code protect, and internal
>Unfortunately, it doesn't seem to show any signs of life. It programs
>and verifies OK, and the simulator suggests that it should be
>initializing I/O ports, etc, but when I hang a logic analyzer off its
>six GPIO pins I see no activity.
What program are you using? You wouldn't necessarily see "activity"
from just initializing the pins. They come up as inputs (high
impedance), even setting them as outputs successfully might not
show up as activity on your logic analyzer.
Make sure you loop your program deliberately, don't just let it
wrap the program counter. A tight loop *toggling* an output pin
(make double sure you are really setting it up as an output, the
pic has the opposite convention for the TRIS compared to most
other micros you might be familiar with) will allow you to
check it out on your logic analyzer, a logic probe or a 'scope.
Oh, cover the window, and if you are using the internal MCLR
bring the power up snappily, not cranked up slowly with your
power supply pot.
Spehro Pefhany --"it's the network..." "The Journey is the reward"
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