Quote:
Originally Posted by SiriusHardware
Ah, right. Changing the value of that pullup resistance may have unintended consequences, as observed earlier. The value seems important, or to be more precise, based on earlier observation, it ideally needs to be no more than 4K7.
If you remember, the capacitors appear to fix some sort of timing relationship between the rate of change of the states of A8-A11 and NWDS but raising the value of the pullup resistor (thereby slowing the rate of change of NWDS) actually cancels out some of the effect of the capacitors.
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Well there's no reason not to change R3 to 4.7k, so that the pullup is always at least 4.7k. With the WE switch closed it will only go down to about 3.2k which isn't going to cause a problem. I will change the schematic appropriately.