In an ISA board I'm testing there is a Dallas DS1321 Nonvolatile
controller used to Convert for banks of SRAM into nonvolatile memory.
The chip is configured to behave so that I conntect to it 4 banks with 1
SRAM each (Mode pin, pin 9 in the 16-Pin DIP case, connected to GND).
Everything works perfectly if I have a battery connected to the Vbat
input (pin 2 of the DS1321 in the 16-Pin DIP case), but, as usually
occurs during testing, I take out the lithium battery, the chip startup
with a different memory configuration. It behaves as Mode pin was left
floating (one banks with 4 RAMS).
I've even connected directly with a wire the GND to this pin, but nothing
changed. Finally I've solved this connecting with a diode/resistor net
that keep the Vbat input below the trip point of 2.6V, but I don't like
this solution. I want to undestand why the device works differently that
what is specified on the Data sheet.
Has someone observed this behaviour previouly?
One final note, the chips I'm using was bought in '99 springs, the data
sheet I've is date september '99, is something changed in the middle?
dott. Ing. Pietro F. Maggi p.maggi AT studiomaggi DOT com