Enormous thanks to all who responded and helped me sort out my dog's
breakfast of an ISR.  It's amazing that anything worked at all, what with W
being trashed so often.  It's now blatantly obvious the port itself was
fine, but was only being observed (as is virtually everything) via the
abused accumulator.  When the revised code ran flawlessly, I felt like
buying a Volvo.  Thanks for being so generous with your time and expertise,
Jan-Erik, Olin, Jinx and Russell.

Rob Robson

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