| Products > Test Equipment |
| Just got a Tek 2465A, couple questions (how I screwed the calibration data)!! |
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| MarkL:
--- Quote from: alpher on March 27, 2018, 06:19:41 pm ---... I'm at loss how it got scrambled so badly? ... --- End quote --- SRAM contents are random after being powered up. The value is dependent on tiny process variations for each bit cell. |
| alpher:
I added a diode in series with vcc pin just in case programmer does something silly, like grounding the pin before reading, just being extra careful here. One resistor pulls the WE pin high also as a precaution, the other is needed because I'm reading it as a plain 27C64 eprom, and pin 26 is not connected there, but on uPD4464 pin 26 is a second chip select CE2 ant it must be high for reading. Somehow my programmer doesn't have an option to read 4464 it can only write!! |
| alpher:
--- Quote from: MarkL on March 27, 2018, 06:43:10 pm --- --- Quote from: alpher on March 27, 2018, 06:19:41 pm ---... I'm at loss how it got scrambled so badly? ... --- End quote --- SRAM contents are random after being powered up. The value is dependent on tiny process variations for each bit cell. --- End quote --- I beg to differ here, static ram sometimes can retain their data even after complete power loss, especialy in low temperature. We're talking relatively short periods of time here, seconds. |
| MarkL:
Perhaps you missed this question... Are you sure that screw pad you soldered to is connected to the ground of the board? Some of those pads could be floating. |
| alpher:
I've checked the resistance, dead short to GND. Something else must have happened, my best guess is that I may accidently somehow touched the vcc pin or anode of the CR2770 to the aluminum standoff while mounting the board back. I was trying to be extra carefull, but who knows. Other than that maybe some sort of static discharge while soldering/desoldering ?, it is pretty dry here in winter. I don't really know. Was hoping somehow that I be able to figure it out from the memory dump (it would be doable if perhaps one byte was bad), but with so many bytes evidently wrong I'm at loss, I think it's hopeless. :'( Anybody knows the way to calibrate these "on a cheap" ? |
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