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FIC 486-VP-IO lose BIOS settings

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First post, by CuPid

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hello,
My FIC 486-VIP-IO (DOC : 13690) does not keep its BIOS settings. The card is in really good shape, and not damaged at all. I got it like this and I don't know if it has ever worked.
It uses a Dallas DS12885Q that is directly soldered on the mainboard. I've checked the VBAT pin with a multimeter and it is well at ~3V. There is no apparent damage.
At that point my knowledge is not complete enough to figure out what could be wrong, and what possible alternate solution I could use to get the problem fixed.
Would someone have an idea ?

Thanks !

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I need a vacation.

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Reply 2 of 9, by CuPid

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evasive wrote on 2020-05-20, 14:06:

Could be a bad flash chip. Do you have another new one to substitute?

Yes I think I could try another one. If that chip was bad would the mainboard boot anyway ?

I need a vacation.

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Reply 6 of 9, by CuPid

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Predator99 wrote on 2020-05-20, 20:47:

No, CMOS data is not stored on the flash.....

What is the status of your J7 (clear CMOS jumper)?

J7 is opened (= normal operation)

quicknick wrote on 2020-05-20, 20:56:

Agreed, CMOS data gets stored on the DS12885. I would try with a 4.5 volts battery pack connected to the external battery header, just to see if anything changes.

Yes good idea.

I need a vacation.

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Reply 7 of 9, by CuPid

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I plugged a 4.5V battery to the external battery header, measured +4.5V on the VBAT pin of the Dallas to be sure, but still settings are not kept after a cold reboot 🙁

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I need a vacation.

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Reply 8 of 9, by quicknick

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From the DS12885 datasheet:

Active-Low RAM Clear. The RCLR pin is used to clear (set to logic 1) all the
general-purpose RAM, but does not affect the RAM associated with the RTC. To
clear the RAM, RCLR must be forced to an input logic 0 during battery-backup
mode when VCC is not applied. The RCLR function is designed to be used
through a human interface (shorting to ground manually or by a switch) and not
to be driven with external buffers. This pin is internally pulled up. Do not use an
external pullup resistor on this pin.

Based on this, check what happens to the RCLR pin when you power off the board, and if it falls to 0 you must find out what's pulling it low.
Another thing, does it reset the time/date also, or only the cmos settings?

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