Re: Programmer troubles with a new twist.

Cameron Rector wrote:
> First of all; I have to say my troubles are looking more and more self
> induced.
>
> I talked to some people on the techtool fourm and got a tip to watch A11
> with a logic probe while programming. Well intresting enough; A11 goes
> high right at 800h and stays high though the rest of the programming
> (that is what it shoud do). So this got me thinking of performing a few
> more tests.
>
> 1. first I loaded a blank eprom into ram, then I viewed the ram and saw
> it was filled with FF (which is correct). Then I performed a verify and
> it passes (and it should). I next loaded my binary file (I am assuming
> its binary) and re-ran verify and it fails (and it should). Then I
> program the ram (containing the file) into the eprom and the post
> program verify fails (and it should not). So I see it fails at 800h (as
> it always does) and it shows ram = 00 and the device = A2 (or something
> simular, I forgot the exact number). So at this point I see from 800h on
> things don't match up. I next load ram again with FF just to make sure
> it is clear and then download the device into ram. I then view the ram
> at 800h and it says 800h = 00. I again run verify and again it fails at
> 800h saying the same thing ram = 00 and the device = A2.
>
> Now how the heck can that happen? I just downloaded the device into ram
> and verified it against its own contents and it fails showing it has a
> different number than what it downloaded.
>
> 2. Just to test the hardware of the programmer. I verified a new blank
> eprom and it passed all FF. I then loaded a constant 00 into ram and
> programmed the eprom and it passes. This tells me that I can take all
> highs at all pins and change them to all lows at all pins. This also
> tell me that the programmer must be doing the hardware thing correctly.
>
> 3. I programmed another blank eprom with an abitrary constant CC and it
> passes. CC is loaded in all locations.
>
> I hope you can follow all of this.
> Thank you for all the help folks!
> Cameron

Definitely a programmer problem. As an experiment, try adding a 4.7 K
(or 4K7 if you're European) resistor from the A11 line to 5 volts at the
EPROM and see if the problem goes away.

Yes, the programmer is taking the A11 line high, BUT HOW FAST. If the
driver is bad (or missing a pullup resistor, if used) you could be
seeing the contents of 0000 instead of 0800 momentarily. To have the
problems you have this would have to be a VERY borderline timing issue.

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Received on Wed Oct 4 15:24:42 2006