Also consider the behavior of the 24-bit data. Is it captured in a register waiting for you to read it or is it a changing value, like a counter.

Your 24-bit read operation will be at least three byte accesses. If the external data value is changing, you may read invalid data.

Here's an example from the Triscend support knowledge base. You'll be asked to log in but it's only like a guest book.

Are There Problems Reading a Multi-byte Counter?
http://portal.knowledgebase.net/article.a...9451&p=171