Electronics > Repair
Looking for Mettler Scale ROM backup
jamarjan:
I swapped the crystal oscillator - the waveforms didn't change
the oscillator waveform itself doesn't look very bad, but the clock waveform from uC is not rectangular
on the other hand, both ADC oscillator waveforms are perfect
My integrated circuit doesn't program at all - it can be read (it's filled with blanks), but it can't be programmed
gmac34 I also ordered RAM d446c - they'll be here tomorrow
dustooff:
Hi,
with regards to the MCU oscillator, I usually scope the ALE and PSEN pins to see if the MCU is trying to access any of the external memory devices, ALE should be 1/8 of the XTAL frequency, see timing waveform on page 25.
If these external memory timing pins are active then the main XTAL clock should be fine.
Then probe each data pin and address pin to check for less than optimal logic levels, sometimes a addr/data line can be stuck.
regards
Andrew
Edit: correction ALE is 1/6 of CLK frequency.
jamarjan:
fzabkar analyzing what you wrote I made a list of my parameters and dumped rom
I'm trying to recreate the configuration of my deleted rom |O
I have problems with positions 10 and 11
can you tell me how to write it correctly
it's a bit strange that the first digit is omitted
I'll stare at this ROM dump for a while :)
jamarjangamc34Model namePM4600hexmod_hexPM4600hex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
fzabkar:
--- Code: ---10: 59 0003B 003B
11: 27136 06A00 6A00
--- End code ---
There is a typo here:
886257 D85F1 85F1
886527 D86FF 86FF <- this is correct
jamarjan:
Hi Andrew and others.
Flashed and reinstalled new EPROM - no changes :'( Still waiting for RAM chip.
On ALE i have a nice square wave of 1,23 MHz
On PSEN similar with a little bit of noise on a high state.
XTAL is about 7,3 MHz
In most cases I have no activity on pins of channel 1 (P1.X) where communication with ROM should be.
Once every few restarts there is activity with waveforms not resembling those I found in the ROM datasheet (in / out).
screenshots attached
These waveforms appear once in a while (every 5th time the scale is used), usually there is no activity or it occurs very shortly after the scale is turned on - I am not able to record it on the oscilloscope.
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