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Just got a Tek 2465A, couple questions (how I screwed the calibration data)!!
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alpher:

--- Quote ---A "spiral-add" checksum for all the cal data is stored at location 0x00.  So, if we know the checksum and we know there's only one bad word, it might be possible to reconstruct the bad word.  I don't know exactly what algorithm they mean by "spiral-add", but it could be figured out.  But then the problem is how to write the correct word back to the EAROM at 0x4C.  That could be done too, but it's not trivial.
--- End quote ---

Mark this is a quote from you on the older thread on 2465 earom, there checksum is located at 0x00 could you elaborate a little what it means?
What I'm driving at is, the location 0x00 is it somehow relative to the location of constants within the earom or is it an "absolute" first location in the chip?
I'd like to know, cause in my case memory dump at 0x00 changes from read to read, in case of 2465A would make more sense to dedicate the whole last 512 Bytes of ram to storage of constants and checksume this area only storing checksum at the end or the beginning.
Do you think that's the case here?
Why it matters ? Cause if that's the case the values that z01z posted should contain the checksum allready since there are a full 512 bytes there.

Here's the z01z data in different form, I marked the first AA constants in red since manual says that many there are,
my guess is that the remainder is for the differnt options perhaps?


--- Code: ---Offset(h) 00   02   04   06   08   0A   0C   0E   10   12   14   16   18   1A   1C   1E
[color=red]
00000000  005B 0675 266A 264D 0637 2627 082E 0822 280B 27FB 0830 0218 221A 221A 2216 2229
00000020  21F7 21FE 01FF 01FC 0212 0068 001F 0020 0023 0020 1C18 3CA8 1D1C 1D94 1FAC 3FA8
00000040  3FA1 3F79 1FB4 0236 0236 2232 2231 1E13 3CA1 3CDA 1000 3FAB 3FA2 3FAB 3FA2 3FAE
00000060  02E4 02E4 02E1 22E0 075C 2834 083C 082B 081B 0839 2823 2065 0836 283B 282F 2820
00000080  2834 081E 2063 2344 0334 2335 2672 2660 2672 065E 02F9 22DC 186B 0E8D 0E90 0724
000000A0  071E 0214 220D 015F 2146 23A9 040F 239A 0326 03D0 0345 230F 0456 0370 02FC 23A6
000000C0  2249 0531 250A 23D4 2596 04B2 04AA 06EC 04D7 03A1 2563 2297 00BF 00C4 20A9 AA66
000000E0  7DA2 032D 851B E8FD 2D47 919F 0440 A1AB 6B25 38B7 DA04 07D6 C003 0484 E87E 6C70
00000100  C76B 9550 6A81 537B F911 3038 D00C 442E 8508 12CE C57E EA21 1421 22FA 3CD5 9DE9
00000120  D8AC 2106 B052 36F9 3FD0 30EB F44E E5AD CB25 08EE E154 0859 BB11 5C93 98CA 844C
00000140  763E F08F 00E8 80C5 764A F152 6E0A 1F6D FA63 7CFD[/color] 4190 E2BA 7B01 30F5 F78E C63F
00000160  F7A8 A479 A4D8 0C53 DE26 14DA 1930 0156 C844 15EC F706 076F A7C8 68DE 6630 FE3F
00000180  FC5B 25B6 6F5B 09F9 0B3B 2D47 2AB8 DC9A 7C29 19FB 93B1 C0F6 03C5 6C9F FF19 1CB1
000001A0  B3C4 9973 FF40 3291 9A10 DACF F98C 88CF BE02 47D7 BE10 089A D46C 0EFB D752 D0FC
000001C0  C73D 28A7 8473 A467 3042 3BCC 9F2A 28FB 838A 148A 9F88 88F8 7F86 F07D 5936 AB8F
000001E0  A7AF C67C 7F64 003E DD5A 2422 322A F7D4 F238 8821 3311 D43B E804 AE72 00CB 0000

--- End code ---
MarkL:

--- Quote from: alpher on March 28, 2018, 02:30:59 pm ---Thank you Mark, now I remember I read your thread awhile ago, if I remember right you were having a similiar issue
only with a plain 2465, how did it end up for you?
Must reread your thread.

--- End quote ---
In that thread there was a user who had one bad value in their 2465 earom (maybe it was a 2445?).  We managed to find which value it was, and further what that calibration constant did (something to do with delta-V cursors).

We then tried to work backwards to replace the bad value by computing trial values with the right parity that would also match the spiral-add checksum for the whole earom.  But because Tek truncated the checksum to 8 bits before storing it, it left many possible combinations for correct solutions.  There was no way to know which match was the original value.

In short, it was a fun exercise but it didn't end up solving the user's issue.  And before anyone says it, yes, a re-cal would have been easier.  But you're missing the word "fun".
MarkL:

--- Quote from: alpher on March 28, 2018, 03:07:44 pm ---
--- Quote ---A "spiral-add" checksum for all the cal data is stored at location 0x00.  So, if we know the checksum and we know there's only one bad word, it might be possible to reconstruct the bad word.  I don't know exactly what algorithm they mean by "spiral-add", but it could be figured out.  But then the problem is how to write the correct word back to the EAROM at 0x4C.  That could be done too, but it's not trivial.
--- End quote ---

Mark this is a quote from you on the older thread on 2465 earom, there checksum is located at 0x00 could you elaborate a little what it means?
What I'm driving at is, the location 0x00 is it somehow relative to the location of constants within the earom or is it an "absolute" first location in the chip?

--- End quote ---
For the 2465, the checksum is stored at an absolute location of 0 in the EAROM.  The EAROM (ER1400) is a bit of an odd thing.  It has 100 locations of 14 bits each and is addressed serially with BCD digits.  It's not in the processor's address space like on the 2465A.


--- Quote ---I'd like to know, cause in my case memory dump at 0x00 changes from read to read, in case of 2465A would make more sense to dedicate the whole last 512 Bytes of ram to storage of constants and checksume this area only storing checksum at the end or the beginning.
Do you think that's the case here?
Why it matters ? Cause if that's the case the values that z01z posted should contain the checksum allready since there are a full 512 bytes there.

--- End quote ---
I think that's inconsistent with the 2465, assuming location 0 is the checksum on the 2465A.  As I recall, the checksum on the 2465 was static.

But you might be right that all you need to do is copy z01z's data to 0x1E00.  Caveats:  There has to be no mistakes in the data, and also that a single capture is consistent with itself (e.g., location 0x00 is not changing while you're capturing everything else, assuming that 0x00 is either the actual checksum, or 0x00 is included in the checksum it if it lives somewhere else).

--- Quote ---Here's the z01z data in different form, I marked the first AA constants in red since manual says that many there are,
my guess is that the remainder is for the differnt options perhaps?
...

--- End quote ---
It could also be settings for the scope that need to be remembered between power ups.  Maybe they're not included in the checksum because if a knob setting is not restored it's not as important, and it's annoying to recompute the checksum every time someone tweaks a knob.  Just a guess.
alpher:
Reacalibration easier?  :o Gues if I had necessary gear, maybe.
Anyway here's the z01z's calibration data in a differnt format, (guess you cannot color within code brackets).
I marked the firts AA contants, according to the service manual there shoul be AA 14bit constants in the 2465A ram CMOS memory.
What worries me is that starting from 6F there are some bigger that that ?  :-//
Should I worry or the manual is wrong here?

Offset(h)     00     02     04     06     08    0A    0C     0E     10    12     14    16     18    1A     1C     1E

00000000  005B 0675 266A 264D 0637 2627 082E 0822 280B 27FB 0830 0218 221A 221A 2216 2229
00000020  21F7 21FE 01FF 01FC 0212 0068 001F 0020 0023 0020 1C18 3CA8 1D1C 1D94 1FAC 3FA8
00000040  3FA1 3F79 1FB4 0236 0236 2232 2231 1E13 3CA1 3CDA 1000 3FAB 3FA2 3FAB 3FA2 3FAE
00000060  02E4 02E4 02E1 22E0 075C 2834 083C 082B 081B 0839 2823 2065 0836 283B 282F 2820
00000080  2834 081E 2063 2344 0334 2335 2672 2660 2672 065E 02F9 22DC 186B 0E8D 0E90 0724
000000A0  071E 0214 220D 015F 2146 23A9 040F 239A 0326 03D0 0345 230F 0456 0370 02FC 23A6
000000C0  2249 0531 250A 23D4 2596 04B2 04AA 06EC 04D7 03A1 2563 2297 00BF 00C4 20A9 AA66
000000E0  7DA2 032D 851B E8FD 2D47 919F 0440 A1AB 6B25 38B7 DA04 07D6 C003 0484 E87E 6C70
00000100  C76B 9550 6A81 537B F911 3038 D00C 442E 8508 12CE C57E EA21 1421 22FA 3CD5 9DE9
00000120  D8AC 2106 B052 36F9 3FD0 30EB F44E E5AD CB25 08EE E154 0859 BB11 5C93 98CA 844C
00000140  763E F08F 00E8 80C5 764A F152 6E0A 1F6D FA63 7CFD 4190 E2BA 7B01 30F5 F78E C63F
00000160  F7A8 A479 A4D8 0C53 DE26 14DA 1930 0156 C844 15EC F706 076F A7C8 68DE 6630 FE3F
00000180  FC5B 25B6 6F5B 09F9 0B3B 2D47 2AB8 DC9A 7C29 19FB 93B1 C0F6 03C5 6C9F FF19 1CB1
000001A0  B3C4 9973 FF40 3291 9A10 DACF F98C 88CF BE02 47D7 BE10 089A D46C 0EFB D752 D0FC
000001C0  C73D 28A7 8473 A467 3042 3BCC 9F2A 28FB 838A 148A 9F88 88F8 7F86 F07D 5936 AB8F
000001E0  A7AF C67C 7F64 003E DD5A 2422 322A F7D4 F238 8821 3311 D43B E804 AE72 00CB 0000

alpher:

--- Quote from: MarkL on March 28, 2018, 03:47:35 pm ---
--- Quote from: alpher on March 28, 2018, 03:07:44 pm ---

Here's the z01z data in different form, I marked the first AA constants in red since manual says that many there are,
my guess is that the remainder is for the differnt options perhaps?
...

--- End quote ---
It could also be settings for the scope that need to be remembered between power ups.  Maybe they're not included in the checksum because if a knob setting is not restored it's not as important, and it's annoying to recompute the checksum every time someone tweaks a knob.  Just a guess.

--- End quote ---

I don't think these are settings of the scope as read the memory many times after I changed the settings, powered it up and down and the last 512 bytes never change.
There's a lot of changes in the lower memory locations though.
I've included a few of the reads in the attached zip file.
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