[volt-nuts] MREAD 3458A

Poul-Henning Kamp phk at phk.freebsd.dk
Thu Aug 26 21:26:19 UTC 2010

In message <4C76C67B.3010101 at freenet.de>, "Dr. Frank Stellmach" writes:

>as far as I remember your recent post, you were not able to read
>all memory locations by MREAD,

You can read any memory location, but you cannot write the CALRAM
(with the MWRITE command) because it is protected by a couple of
layers of protection in hardware.

You can write the CALRAM by downloading a M68K program that does
the right gyrations to open the protection mechanisms.  There does
not seem to be any published data on this however, I had to disassemble
the code in the ROMS to find out how that worked.

But if you read a copy with MREAD and save that, you can always
program a new CALRAM chip in a EPROM-programmer or by other means.


Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
phk at FreeBSD.ORG         | TCP/IP since RFC 956
FreeBSD committer       | BSD since 4.3-tahoe    
Never attribute to malice what can adequately be explained by incompetence.

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