There are a group of obscure internal properties exposed
to protect against an hardware defect in certain batches of
the B7 die of some DS18x20 chips. See
http://www.1wire.org/en-us/pg_18.html or request AN247.pdf
from Dallas directly.
Two character manufacturing die lot. "B6"
"B7" or "C2"
32 bit trim value in the EEPROM of the chip. When written,
it does not seem to read back. Used for a production problem
in the B7 Read allowed for all chips. Only the B7 chips can
be written.
Writing non-zero (=1) puts a default trim value in the chip.
Only applied to the B7 Reading will be true (non-zero) if
trim value is the blanket value. Again, only B7 chips will
register true, and since the written trim values cannot be
read, this value may have little utility.
Is the value in the valid range? Non-zero if true, which
includes all non-B7 chips.