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Robbyrobot
Interesat
Joined: 09 Sep 2007
Posts: 22
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 Posted: Fri Dec 07, 2007 7:05 pm Post subject: Conflicting Information, Please Clarify |
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In another thread, Victor notes:
| Quote: | ---When itester shows 1,
-the SCL must have 5.1V exaclty. If not the zener ain't good.
-SDA must have between 4.0-4.8V
---when itester shows 0:
Bothe SCL and SDA must show -(negative) 0.6V |
However, the information in the help function of Itester says:
| Quote: | | SDA &SLC signals will trigger betwen 1 and 0., after each 5 seconds. The output voltage should be 3.3-5V in high state (1) and 0.6V in low state (0). |
Now, I have built the SIPROG interface and have tested it on both a desktop computer and a laptop using Itester. The results I get are
SDA: -0.73/4.33V
SCL: -0.73/4.47V
The values vary only slightly from one computer to the other, and also only slightly from one multimeter to another (I tried two).
So my question is whether my interface has a problem, or if the values I get are within normal variation? If I go by what Victor said in the other thread, my interface must be defective (although how this should happen is a mystery to me), but if I go by the information in the help function of Itest, the values I get are reasonable.
Could you please clarify? |
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bob
S.F. Moderator
Joined: 07 Mar 2004
Posts: 802
Location: Staff
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| Posted: Sat Dec 08, 2007 12:50 am Post subject: |
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I would do that for you:
- the 5V1 zeners always give 5.1Volts, your zener could be 4V3 or the port's level is just 4.3 ( I bet it is not), that does not reach the zener's trigger. Too complicated?
Let put it this way, TTL logics need above 2.7V (3.3V would be perfect), so if your interface is showing this, it should work.
The SDA level could be a bit lower because of the SDA in impedance, the quote from Victor is from a post where he explained to a guy what is the process with SIPROG.
itester help window refers basicaly to the driven programmer which has the same output level (3.3-5V) for both signals, but the voltage is depending on what chip you use MAX232 or MAX3232, etc. No matter as long as the TTL (1) requires 3.3 V, everything is fine... |
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Robbyrobot
Interesat
Joined: 09 Sep 2007
Posts: 22
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| Posted: Sat Dec 08, 2007 10:58 am Post subject: |
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| Quote: | | - the 5V1 zeners always give 5.1Volts, your zener could be 4V3 or the port's level is just 4.3 ( I bet it is not), that does not reach the zener's trigger. Too complicated? |
Not really, just surprising, as I bought the zeners at an electronics shop where the owner himself is en electronics professional. I asked for 5.1V zeners and would have expected to get just that. Anyway, I agree that the port level probably has nothing to do with my readings, since the values were nearly identical for both the desktop and the laptop.
| Quote: | | No matter as long as the TTL (1) requires 3.3 V, everything is fine... |
And that's the main thing. Thanks for the clarification!
A few hours later...
And now I can report complete success on the first try removing the password from my T23 board.
Hooked up the probes to the 24RF08 /SDA and SCL only), put the alligator clip for the ground on the metal RAM clip and immediately got a good dump from which I had no problems extracting the password. I removed the password from the board and then got a dump of the non-passworded 24RF08 just to be prepared for possible future problems like CRC errors.
After all my fears, caution and procrastination, I was amazed how simple the procedure actually was. But of course that's only because you and the other people at ALLservice have generously made things this simple - and deserve great thanks for your efforts. |
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