Service Forum

[mgreig]

I've assembled the simple interface following the directions and photos carefully. The GND, SDA and SCL are soldered (with much sweating!) to the Amtel. Thanks to all, especially Victor on this forum for all the instructions and comments. The zeners are 5.1V and the resisters are 2200 ohms.

My COM port seems to be running at about 11 volts. Running iTester shows the SDA value to be at 1 all the time, and the SDA/SCL Out value alternating between 0 and 1.

Victor posted (in August 2006) that the SIPROG to SDA should be 3.3V Hi/-0.6V Lo and the SIPROG to SCL should be 5.1V Hi/-0.6V Lo. But on my board, I'm testing the SIPROG to SDA at +4.0V/+0.9V and the SIPROG to SCL at +4.0V/-0.9V.

I know that this isn't right and of course I'm getting the "Error: eeprom not available message" but I'm now over my head.

Any suggestions as to what I might be doing wrong?

[victor]

Hello,

I wrote that for SIPROG, SDA should be between 3V..5.1V. Due to CTS pin internal pedance, the voltage is usually below 5.1V.
What is important is that both SCL and SDA to not override 5.1V, or zeners are not working. When itester shows "0" the voltage is negative -0.5..-0.7V, or the COM port is not doing so well.

When running itester, make sure the SDA and SCL are disconnected from the eeprom.
_________________
Victor Voinea
ALLservice HQ, Romania.

[mgreig]

Thank you Victor. The first mistake I made was running iTester with the SCL and SDA leads connected to the eeprom.

Now, when using iTester (and the SDA and SCL) disconnected the the SDA In and the SDA/SCL Out indicators both change from 1 to 0 every five seconds or so together. That's good, right?

Now for the bad part. I'm testing across the zener diodes (postive tester lead on the cathode/+ side and the negative tester lead to the anode/- side) and the values are:

SCL +4.1V Hi (1) and -0.71V Lo (0)
SDA +2.4V Hi (1) and -0.71V Lo (0)

Is the SDA voltage too low? Is it a problem with the serial port? Am I testing the voltage correctly?

Any suggestions would be much appreciated. Thank you.

[victor]

Yes, 2.4 is low! when the eeprom is wired on, it will be under 2V so the SDA will stay on 0 all the time, at no avail.

Possible causes:
1. The resitors are of wrong value, I mean way higher than 2.2Kohms.
Solution: Check them with an ohmeter and replace if necessary.

2. The internal CTS impedance is lower than normal. This doesn't mean the port is not working, only that it can't support the simple programmer.
Solution: Obviuosly you have two choices: use another PC with a more reliable port or build the driven programmer.

Good luck!
_________________
Victor Voinea
ALLservice HQ, Romania.

[mgreig]

Thanks Victor, you are absolutely right!

I checked the resisters and they were 22,000 ohms!! I replaced them with 2200 ohms and now my SCL is +4.9V/-0.77V and the SDA is +4.69V/-0.78V.

iTester shows both SDA In and SDA/SCL Out alternating 1's and 0's as it should.

I ran 24RF08 and was successful in creating a 1024 byte capture of the eeprom's contents

Now, I'm a little baffled by the .bin file contents. In IBMPass 2.1 Lite (with AA On) the code at 0x338 and 0x340 is the same: "3670= " and I'm not sure how to interpret this. Can you help?

[victor]

I think is TCPA locked but to be sure gotta see it. support@ is the address.
_________________
Victor Voinea
ALLservice HQ, Romania.

[victor]

Ok, your R31 is using Alternate scancode, use Shift+F2 in IBMpass (AA must be ON). Well done!
_________________
Victor Voinea
ALLservice HQ, Romania.

[mgreig]

Victor, you're amazing.

Thank you for all your help.