DS1977 查看數據表（PDF） - Maxim Integrated
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DS1977 Datasheet PDF : 29 Pages
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DS1977
Read Access Password
This password only applies to the function "Read Memory with Password”. If passwords are enabled (EPW = AAh,
see Password Control register), the 64-bit data pattern that the 1-Wire master has to transmit with the command
flow is compared to the passwords stored in the DS1977 iButton. The DS1977 delivers the requested data only if
the password transmitted by the master was correct or if password checking is not enabled.
Read Access Password Register
ADDR b7
b6
b5
b4
b3
b2
b1
b0
7FC0h RP7 RP6 RP5 RP4 RP3 RP2 RP1 RP0
7FC1h RP15 RP14 RP13 RP12 RP11 RP10 RP9 RP8
—
—
—
7FC6h RP55 RP54 RP53 RP52 RP51 RP50 RP49 RP48
7FC7h RP63 RP62 RP61 RP60 RP59 RP58 RP57 RP56
There is only write access to this register. The Read Access Password needs to be transmitted exactly in the
sequence RP0, RP1… RP62, RP63.
Full Access Password
This password applies to the functions "Read Memory with Password” and "Copy Scratchpad with Password”. If
passwords are enabled (EPW = AAh, see Password Control register), the 64-bit data pattern that the 1-Wire
master has to transmit with the command flow is compared to the passwords stored in the DS1977 iButton. The
DS1977 executes the command only if the password transmitted by the master was correct or if password
checking is not enabled.
Full Access Password Register
ADDR b7
b6
b5
b4
b3
b2
b1
b0
7FC8h FP7 FP6 FP5 FP4 FP3 FP2 FP1 FP0
7FC9h FP15 FP14 FP13 FP12 FP11 FP10 FP9 FP8
—
—
—
7FCEh FP55 FP54 FP53 FP52 FP51 FP50 FP49 FP48
7FCFh FP63 FP62 FP61 FP60 FP59 FP58 FP57 FP56
There is only write access to this register. The Full Access Password needs to be transmitted exactly in the
sequence FP0, FP1… FP62, FP63.
Password Control Register
The data pattern stored in the Password Control Register determines whether password checking is enabled. If
password checking is enabled, the password transmitted is compared to the passwords stored in the device.
Reading from or writing to the scratchpad does not require a password.
Password Control Register Bitmap
ADDR b7
b6
b5
b4
b3
b2
b1
b0
7FD0h
EPW
Register Details
BIT DESCRIPTION
EPW: Enable Passwords
BIT(S)
b0 to b7
DEFINITION
This byte enables or disables the password protection, which applies
to reading from and writing to the memory except for the scratchpad.
If the EPW bits form a pattern of 10101010 (AAh), the device will
execute these commands only if the correct password is transmitted.
The default pattern of EPW is different from AAh.
To enable password checking, the EPW bits need to form a binary pattern of 10101010 (AAh). If the EPW pattern
is different from AAh, any password will be accepted, as long as it has a length of exactly 64 bits. Before enabling
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