DS1922T-F5 MAXIM [Maxim Integrated Products], DS1922T-F5 Datasheet - Page 23

• Manufacturer Part Number: DS1922T-F5
• Description: Temperature Logger iButton With 8kB Datalog Memory
• Manufacturer: MAXIM [Maxim Integrated Products]

Device Configuration Byte
There is only read access to this register.
SECURITY BY PASSWORD
The DS1922L/T is designed to use two passwords that control read access and full access. Reading from or writing
to the scratchpad as well as the forced conversion command does not require a password. The password needs to
be transmitted right after the command code of the memory or control function. If password checking is enabled the
password transmitted is compared to the passwords stored in the device. The data pattern stored in the Password
Control register determines whether password checking is enabled.
Password Control Register
During a mission, there is only read access to this register.
To enable password checking, the EPW bits need to form a binary pattern of 10101010 (AAh). The default pattern
of EPW is different from AAh. If the EPW pattern is different from AAh, any pattern will be accepted, as long as it
has a length of exactly 64 bits. Once enabled, changing the passwords and disabling password checking requires
the knowledge of the current full-access password.
Before enabling password checking, passwords for read-only access as well as for full access (read/-
write/control) need to be written to the password registers. Setting up a password or enabling/disabling 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 redefined at the same
time.
Read Access Password Register
There is only write access to this register. Attempting to read the password will report all zeros. The password
cannot be changed while a mission is in progress.
The Read Access Password needs to be transmitted exactly in the sequence RP0, RP1… RP62, RP63. This
password only applies to the function “Read Memory with CRC”. The DS1922L/T will deliver the requested data
only if the password transmitted by the master was correct or if password checking is not enabled.
Full Access Password Register
ADDR
ADDR
ADDR
022Eh
022Fh
ADDR
0226h
0226h
0226h
0226h
0227h
0228h
0229h
0230h
0231h
0236h
0237h
—
—
b7
RP15
RP55
RP63
FP15
FP55
FP63
0
0
0
0
RP7
FP7
b7
b7
b7
b6
0
0
1
1
RP14
RP54
RP62
FP14
FP54
FP62
RP6
FP6
b6
b6
b6
b5
0
1
0
1
b4
RP13
RP53
RP61
FP13
FP53
FP61
0
0
0
0
RP5
FP5
b5
b5
b5
b3
0
0
0
0
RP12
RP52
RP60
FP12
FP52
FP60
RP4
FP4
b4
b4
b4
…
—
b2
0
0
0
0
EPW
b1
RP11
RP51
RP59
FP11
FP51
FP59
0
0
0
0
RP3
FP3
23 of 50
b3
b3
b3
b0
0
0
0
0
RP10
RP50
RP58
FP10
FP50
FP58
RP2
FP2
b2
b2
b2
DS2422
DS1923
DS1922L
DS1922T
RP49
RP57
FP49
FP57
RP1
RP9
FP1
FP9
b1
b1
b1
RP48
RP56
FP48
FP56
RP0
RP8
FP0
FP8
b0
b0
b0
—
—
DS1922L/DS1922T