> I like to know what is RMW? and shadow register?

A graphical example of rmw. An SX pin driving a CMOS 4000

http://sxlist.com/techref/scenix/sxrmw.htm

Back in the days when I thought, nah, rmw will never get me .....

The solution here was to use either a shadow register or extra
nops, and it worked perfectly thereafter. Amazing how such a
simple and, at the time, elusive, problem can be so frustrating

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