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SiriusHardware · 25th Feb 2022, 6:13 pm

I didn't look too closely but I thought the protect-from-write on supply failure was implied by the fact that the active-low CE lines pass through the transistors, so when the power fails the RAM CE pins are disconnected from anything which can pull them low, preventing write operation.

At the same time, the battery maintains the +5V supply to the RAM but its power consumption is very low when CE is not asserted.

Having actually used that Maplin CPU (I still have it) I can't recall it ever losing or corrupting the backed up memory contents, unless of course I left it for so long that the battery ran down.

25th Feb 2022, 6:13 pm	#18
SiriusHardware Dekatron Join Date: Aug 2011 Location: Newcastle, Tyne and Wear, UK. Posts: 11,586	Re: Genuine DS1210 NVRAM controllers I didn't look too closely but I thought the protect-from-write on supply failure was implied by the fact that the active-low CE lines pass through the transistors, so when the power fails the RAM CE pins are disconnected from anything which can pull them low, preventing write operation. At the same time, the battery maintains the +5V supply to the RAM but its power consumption is very low when CE is not asserted. Having actually used that Maplin CPU (I still have it) I can't recall it ever losing or corrupting the backed up memory contents, unless of course I left it for so long that the battery ran down.