HT-CM400 NXP Semiconductors, HT-CM400 Datasheet - Page 99

• Manufacturer Part Number: HT-CM400
• Description: Ht Cm400; Ht Rm440 Family; Ht Rm800 Family Interface Protocol Reader - Host
• Manufacturer: NXP Semiconductors

98-02-10
5.3.2.2 Incorrect Procedures Changing Keys
The same scenario applies if you first change one or both of the keys on the transponder but leave
the keys on the read/write device unchanged (transport keys).
ATTENTION:
If neither Key A nor Key B of the transponder and the read/write device are identical, you
cannot access the secret area on that transponder! Access to the plain area of the
transponder (e.g. serial number) is possible in any case.
5.3.2.3 Changing Logdata
To change logdata use the same procedure as described for changing keys. Be careful to change
them by pairs (on the read/write device and on the transponder):
1.
2.
3.
4.
Again, you need to know the old values before they can be changed on the read/write
device.
For changing the logdata of a big number of tags we recommend to doing it in the same way as
described in the former chapter „Changing Keys“ in the note.
When you change a key, this does not mean that you also have to change the corresponding
logdata and the other way round.
You change both keys on the read/write device and then try to access the transponder. This is
not possible because there is no identity between any of the keys on the transponder and the
read/write device.
You change only one key (e.g.: Key A) on the read/write device; the second key (in this
example B) remains the Transport Key. Then you try again to access the transponder. This can
be possible, only if your system works with both keys and checks one after the other, because
one key (here it is Key B) on the transponder and the read/write device is still identical.
Change, for example, Logdata 0A on the transponder (by overwriting Page 5).
Change Logdata 0A on the read/write device to the new value.
Change Logdata 1A on the transponder (by overwriting Page 6).
Change Logdata 1A on the read/write device to the new value.
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