Jay Francis wrote: : Hi Dennis, :> For the sake of argument, I'll respond, heck, :>maybe someone will see something that I missed.
: I'm glad you responded. My intent was to help, I hope I didn't offend! : Sometimes asking the obvious and/or basic questions leads to the solution. Anyone that is easily offended should stay off the 'net.
: They usually lead me to a "Homer Simpson" moment... Doh!!! :>my MEGA8535 doc stops at figure :>130, where did you get yours?
:
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The revision in the lower right corner of each page is 2502D-AVR-09/03.
I must have gotten a very early preliminary one, I downloaded the new one and gots LOTS of new info that wasn't in the one that I had. Still, finding fuse settings in there is like searching for a needle in a haystack, or rather 4 parts of a needle in different places of the haystack...
:> I found that it did not properly reset the board on power up, that is the :>reason that I added the supervisor.
: I think this is a clue that something basic isn't quite right.
Indeed.
: Are you using the MEGA8535 or the MEGA8535L? I'll assume the MEGA8535, since : the L part has a maximum frequency of 8MHz, but let me know.
: Do you have the CKOPT fuse programmed (page 24 of the datasheet)?
I did not explicitly set this. I'll check on that one.
: Note 3 for Table 15 is interesting. Maybe your part snuck through without : being "production tested" for that parameter? You might want to try a DS1233-5 : to tighten the reset tolerance to be in line with the 4.5V minimum VCC spec of : the micro.
: What if you went back to using the on-chip power on reset and brown out : detection - but do not add any external components to the reset line (in a : previous post you mentioned having an R/C circuit on the reset line)?
:> I've looked, but for the life of me I don't find a register that tells :>me that I just had a reset
: In the datasheet I have, page 38 shows the MCUCSR register.
Yeah, I found that right after I posted. "Doh!"
:>10K, .1uf, well in the spec for the chip, which is a ds1233-10, so 4.25 to :>about 4.5V is the trip point.
: Not to be too picky, but the DS1233 datasheet recommends between 100pf and : 0.01uF when using a pushbutton switch. Do you have a switch connected?
: The internal pullup is between 3.75K and 6.25K, so your 10K resistor brings the : total resistance between 2.7K and 3.8K. Do you still have the problem with the : cap and resistor removed?
I'll try some more of these tests and checks. Some part swaps, etc. My standard RC for reset is 10K, .1uf - The DS1233 was "cockroached" on, that is why the older RC is still there, it seemed like it wasn't contraindicated as a bad combination.
: Random questions:
: What type of scope are you using to look at the VCC and reset lines?
25MHz analog scope.
: What if you run the processor slower? (i.e. 8MHz, if it doesn't require a ton : of software changes)
I noted some settings in the clock section were not recommended when running the clock near maximum settings, which I am - when all else fails, I'll try dropping the frequency.
: --Jay
You've given a wealth of insight here. I am an old hand at the PICs, but this is one of my early sortees into using Atmel as a controller, so I'm not yet hip to all of the caveats.
thanks, ============================================================================
- Dennis Clark snipped-for-privacy@frii.com
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*
- "Programming and Customizing the OOPic Microcontroller" Mcgraw-Hill 2003 * ============================================================================