On Sun, 19 Oct 2003, Ken Pergola wrote:

> Would you mind given me a lesson on the caveats of using string packing?

The string packing code places two seven-bit ASCII characters in one
14-bit program word, and relies on the ability to read program memory
to fetch a string.  It's not always safe to assume program memory can
be read, since the PIC's interface to program memory is shared with
its interface to internal EEPROM.  This could be a problem, for
example, if you have an interrupt-driven EEPROM write queue.  Say
you're in the middle of transferring a packed string to your LCD, and
EEIF pops.  When your ISR returns, the string unpacking code continues
reading program memory, which fails because an EEPROM write is in
progress.

--
John W. Temples, III

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