Hi David,

I think, there are many stages with several delay times involved to generate RD/WR from XTAL2.

So under some conditions it can be, that the falling edge generate RD/WR. But on lower crystal, temperature or voltage it can be the opposite.
This meets still the data sheet, since never any maximal or minimal timing parameters defined related to XTAL2.

So any usage, which need such relations should fail.

Nevertheless XTAL2 can be used as clock for peripherals. E.g. I use it for the LAN91C96. But this chip need no special relations between clock and the RD/WR inputs.


Peter