10 Jul
2006
10 Jul
'06
2:20 p.m.
The 6522 is sometimes nice but hard to find. and for
many the 68721 is
even harder to find.
As someone said, 8255s, the roads paved with them. Also how often do
you have to turn a port around? Apps where I needed that I found that
there were other approaches that worked better.
A trivial example that I have done many times : You can bit-bang I2C
through a couple of port lines on a 6522 (or 6821), and all you have to
add is a couple of pull-up resistors. You can't do it with an 8255 so
easily (you need 2 ouputs, 2 inputs, and external buffers).
-tony