Datasheet

DS1922L/DS1922T
Temperature Logger iButton with 8KB
Data-Log Memory
26 ______________________________________________________________________________________
Before enabling password checking, passwords for
read-only access as well as for full access
(read/write/control) must be written to the password
registers. Setting up a password or enabling/dis-
abling the password checking is done in the same
way as writing data to a memory location; only the
address is different. Since they are located in the
same memory page, both passwords can be rede-
fined at the same time.
The Read Access Password must be transmitted exact-
ly in the sequence RP0, RP1…RP62, RP63. This pass-
word only applies to the Read Memory with CRC
function. The DS1922L/DS1922T deliver the requested
data only if the password transmitted by the master was
correct or if password checking is not enabled.
The full-access password must be transmitted exactly
in the sequence FP0, FP1…FP62, FP63. It affects the
functions Read Memory with CRC, Copy Scratchpad,
Clear Memory, Start Mission, and Stop Mission. The
DS1922L/DS1922T execute the command only if the
password transmitted by the master was correct or if
password checking is not enabled.
Due to the special behavior of the write-access logic,
the Password Control register and both passwords
must be written at the same time. When setting up new
passwords, always verify (read back) the scratchpad
before sending the Copy Scratchpad command. After a
new password is successfully copied from the scratch-
pad to its memory location, erase the scratchpad by fill-
ing it with new data (Write Scratchpad command).
Otherwise, a copy of the passwords remains in the
scratchpad for public read access.
Read Access Password Register Bitmap
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0228h RP7 RP6 RP5 RP4 RP3 RP2 RP1 RP0
0229h RP15 RP14 RP13 RP12 RP11 RP10 RP9 RP8
… …
022Eh RP55 RP54 RP53 RP52 RP51 RP50 RP49 RP48
022Fh RP63 RP62 RP61 RP60 RP59 RP58 RP57 RP56
Full Access Password Register Bitmap
ADDRESS BIT 7 BIT 6 BIT 5 BIT 4 BIT 3 BIT 2 BIT 1 BIT 0
0230h FP7 FP6 FP5 FP4 FP3 FP2 FP1 FP0
0231h FP15 FP14 FP13 FP12 FP11 FP10 FP9 FP8
0236h FP55 FP54 FP53 FP52 FP51 FP50 FP49 FP48
0237h FP63 FP62 FP61 FP60 FP59 FP58 FP57 FP56
Note: There is only write access to this register. Attempting to read the password reports all zeros. The password cannot be
changed while a mission is in progress.
Note: There is only write access to this register. Attempting to read the password reports all zeros. The password cannot be
changed while a mission is in progress.