[volt-nuts] Prema 6048 Cal switch confusion

[Tom Miller]

How about copying the contents of the old nvram to the new one?


----- Original Message ----- 
From: "David C. Partridge" <david.partridge at perdrix.co.uk>
To: "'Discussion of precise voltage measurement'" <volt-nuts at febo.com>
Sent: Thursday, November 02, 2017 2:58 PM
Subject: Re: [volt-nuts] Prema 6048 Cal switch confusion


> Update - when I tried this I was using a brand new DS1220AD-100IND (blank) 
> to replace the DS1220Y.
>
> Reinstalling the DS1220Y and it worked as expected!  Processor must detect 
> cal mode by writing to NVRAM - if succeeds, then in Cal mode??? Maybe
>
> Is there some obscure incompatability between the DS1220AD and the 
> DS1220Y???
>
> Dave
>
> -----Original Message-----
> From: volt-nuts [mailto:volt-nuts-bounces at febo.com] On Behalf Of David C. 
> Partridge
> Sent: 02 November 2017 18:23
> To: 'Discussion of precise voltage measurement'
> Subject: [volt-nuts] Prema 6048 Cal switch confusion
>
> I've got a Perma 6048 that I've trying to put into Cal mode.  It just 
> won't!
>
> The switch on the rear panel works OK, AFAICT when in the Cal position it 
> connects ~WE on the DS1220 (pin 21) and ~W on the $864 SRAM (pin 27) to a
> 4K7 pullup to +5V and to the output of an LS00 which should be strobing 
> the
> Write lines low as needed.   I can't see any way in which the processor 
> can
> be informed of the switch setting!  In measure mode it just connects ~WE 
> on the DS1220 to a 10k pullup to +5V.
>
> The schematic is on page 120 (Figure 11.4) of the user manual and also 
> page
> 9-7 of the service manual.
>
> Clearly I'm missing something - as a friend reports that his does go into 
> cal mode.
>
> Confused ...
> Thanks
> Dave
>
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