[time-nuts] Dallas NV-SRAM replacement? (in 3458A)
phk at phk.freebsd.dk
Tue Jun 8 18:05:32 UTC 2010
In message <20100608164407.A9783112AD9 at mail.ebirds.it>, Marco IK1ODO -2 writes:
>Speaking of the 3458A, it has three DS1235Y-150 non volatile SRAM on
>the CPU board. Each is a 32K x 8 bit, so there is a lot of info inside.
>As the useful life of those is in the order of 10 years and most
>3458A a re now 10 to 20 year old, is there a possible replacement?
>Possibly with a more modern component?
I replaced all the NVRAM's in mine last month, no issues.
There are plenty of NVRAMs to be had as new.
>Also, of course it would be a good idea to read and save the contents
>of the SRAMs before replacing, but... is any custom data in them that
>cannot be rewritten with a complete recalibration?
The CALRAM contains a number of "magic" counters, one of which is
called "destructive overloads" that a calibration cannot possibly
But from a functional point of view: no.
You can read out the memory with the undocumented "MREAD" command,
but the CALRAM is protected by various tricks, so you cannot just
use the MWRITE command to restore it.
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