Richard -

You could generate e-clock, though perhaps not in the way you suggest. We use e-clock to trigger the hand shaking strobes, and did the design under the assumption that it always ran.

Your method generates a single e-clock for the R/W cycle, and I suspect that the strobes would not work correctly. I think that there would need to be a few more e-clocks before everything settled out.

I must admit that I did this chip back in 1999, and I am pushing my memory here. I would have to pull out the design files to make sure.

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The 6811 was designed to interface with the 6824. There are even dual-mapped registers between the two devices. It is really simple to hook them together, since all of the hard work is done in hardware. I think this is a case where the Motorola (now Freescale) engineers learned from Intel's mistakes.

Had Intel done as good a job, then half the threads on this forum (8255) wouldn't be here.