Re: Which programmer to use to read/write dallas DS1486?


 

On Mon, Sep 21, 2020 at 08:31 AM, tgerbic wrote:


The info in the datasheet is probably not clear because "you should not need
to know this". Based on looking at this and other family datasheets it seems
as if the difference between the W and non-W version is the power fail voltage
level. Both chips seem to be ok with 6V on any pin so I suspect they both work
on 5V but the W version should not be used in a 5V environment because of the
power fail level being so low. This is just a guess from looking at the
datasheets so it is your choice to try it. I would probably pop it into my
Xeltek or Unisite and program it that way but if I did not have either, I
would try programming as a 5V part.
Alternately, if you are worried, you could try the Arduino driving SRAM method
I mentioned to Rogerio on this thread. In that case you could drive it at
3.3V.

I ran into a similar won't work problem with one of my HP 16xx logic analyzers
and its LAN interface. Turns out if the MAC address is not programmed in Flash
(battery died in a timekeeping device), the LAN interface will not come up at
all. I just programmed in a typical value for an HP device (random MAC) and it
came right up. Guess this is the same as your problem.
Hi Tony,
Thanks for your comments. 5 V seemed to be OK for the DS1742W because the data sheet made no distinction between the 3.3 V and 5 V version re. Vcc max. and the idea that the difference in Vpf did not indicate any other differences in the chip.
That was until I saw the data sheet of newer devices, where a Vcc max of 4.6 V is specified for the 3.3 V part. Could all be the reason you mentioned but I have no spare DS1742W in case it dies and can't easily get one, although alternatives exist. That's the main reason for being so careful and hesitant.
I decided to connect/cloak my DS1742W as a DS1750W, although the latter is much larger but it's supported in my programmer (TL866II Plus). Connecting the DS1742W seems quite easy, with most pins straight through and just two wiring changes.
I'll keep your hint re. an Arduino in mind.

ISTR a similar problem with HP's 16702A/B LA's.

Raymond

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